piece at age 6. Girolamo Fracastoro Viruses, Bacteria ... · 1903 The Pittsburgh Pirates and ......
Transcript of piece at age 6. Girolamo Fracastoro Viruses, Bacteria ... · 1903 The Pittsburgh Pirates and ......
Viruses BacteriaProtists andFungiWhat Yoursquoll LearnChapter 18
Viruses and Bacteria
Chapter 19Protists
Chapter 20Fungi
Unit 6 ReviewBioDigest amp Standardized Test Practice
Why Itrsquos ImportantAlthough the world we encounter is largely limited to what we can see that representation is misleading Even though the world is filled with plants and animals that are easily distinguishable much of the real diversity lies in the things we cannot see We rely on bacteria and fungi to act as decomposers that keep nutrients cycling through the food chain In addition to bacteria nonliving things such as viruses act as disease agents on both plants and animals
1546Girolamo Fracastorotheorizes that dis-eases are caused byinvisible organisms
Understanding the PhotoThese Coprinus mushrooms grow in thickclumps on the forest floor The mushroomsare the reproductive forms of the funguswhich lives mostly underground and getsnutrition by decomposing the organisms thatfall to the forest floor
472
1761Wolfgang Amadeus Mozartcomposes his first musicalpiece at age 6
Taylor F Lockwood
cabdolglencoecomwebquest
The following standardsare covered in Unit 6Investigation andExperimentation 1k 1mBiologyLife Sciences 1c 1d
California Standards
0472-0473 UO6 BDOL-829900 8404 624 PM Page 472
1815Francersquos armiesare defeated atWaterloo
1861A funguslike protist causes the Irish potatoblight leading to a mass famine
1892The first virustobacco mosaicvirus is identified
1941Penicillin is first used as an antibioticfor humans
2002The genome for theparasite that causesmalaria is fullysequenced
1796Edward Jennerintroduces thefirst vaccine inorder to pre-vent smallpox
1903The Pittsburgh Pirates andthe Boston Red Sox play inthe first World Series
473
A political drawingduring the Irishpotato blight
Color-enhanced TEMMagnification 30 000
Tobacco mosaic virus
(tl)HultonArchive (tr)Scott CamazineSS Billota BestPhoto Researchers
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474Eye of SciencePhoto Researchers
Visit tobull study the entire chapter
onlinebull access Web Links for more
information and activities onviruses and bacteria
bull review content with theInteractive Tutor and self-check quizzes
Viruses cannot function withouta host This photo taken withan electron microscope shows agroup of viruses called phagesinfecting an E coli bacteriumThe viruses have attached them-selves to the outside of the bac-terium and are injecting it withtheir nucleic acid
Understandingthe Photo
What Yoursquoll Learn You will identify the struc-
tures and characteristics ofviruses and bacteria
You will explain how virusesand bacteria reproduce
You will recognize the med-ical and economic importanceof viruses and bacteria
Why Itrsquos ImportantViruses and bacteria are impor-tant because many cause diseasesin plants and animals Bacteriaplay an important role in creat-ing foods and drugs as well ashelping to recycle nutrients
Viruses and BacteriaViruses and BacteriaColor-enhanced SEM Magnification 90 000
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181SECTION PREVIEWObjectivesIdentify the differentkinds of viruses and theirstructuresCompare and contrastthe replication cycles ofviruses
Review Vocabularynucleic acid a complex
macromolecule eitherRNA or DNA that storesgenetic information (p 163)
New Vocabularyvirushost cellbacteriophagecapsidlytic cyclelysogenic cycleprovirusretrovirusreverse transcriptaseprionviroid
181 VIRUSES 475
What is a virusYoursquove probably had the flumdashinfluenzamdashat some time during your life
Nonliving particles called viruses cause influenza Viruses are composedof nucleic acids enclosed in a protein coat and are smaller than the small-est bacterium To appreciate how very tiny viruses are try the MiniLab onthe next page
Most biologists consider viruses to be nonliving because they donrsquotexhibit all the criteria for life They donrsquot carry out respiration grow ordevelop All viruses can do is replicatemdashmake copies of themselvesmdashandthey canrsquot even do that without the help of living cells A cell in which avirus replicates is called the host cell
Because they are nonliving viruses were not named in the same way asorganisms Viruses such as rabies viruses and polioviruses were namedafter the diseases they cause Other viruses were named for the organ ortissue they infect For example scientists first found the adenovirus (uh DEN uh vi ruhs) which is one cause of the common cold in adenoidtissue between the back of the throat and the nasal cavity
Today most viruses are given a genus name ending in the word ldquovirusrdquoand a species name However sometimes scientists use code numbers todistinguish among similar viruses that infect the same host For exampleseven similar-looking viruses that infect the common intestinal bacteriaEscherichia coli have the code numbers T1 through T7 (T stands forldquoTyperdquo) A virus that infects a bacterium is called a bacteriophage(bak TIHR ee uh fayj) or phage for short
Getting a VaccinationUsing Prior Knowledge As a child you probably received several vaccines Children are regularly vaccinated against diseases that could otherwise be life threatening Vaccines are injections of particles of viruses or bac-teria that provide the human body with a defense against disease Thanks to vaccines many devastating diseases of the past are now rarely encounteredResearch Make a list of the vaccines you received as a child Next to each vaccine list the disease that the vaccine prevents and what microorganism causes the disease
Viruses
Aaron HauptPhoto Researchers
Children are vaccinated againstseveral diseases
Standard 1c Students know howprokaryotic cells eukaryotic cells and viruses differ incomplexity and general structure
California Standards
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BDOL-181
null
7444423
Viral structureA virus has an inner core of nucleic
acid either RNA or DNA and an outerprotein coat called a capsid Some rel-atively large viruses such as human fluviruses may have an additional layercalled an envelope surrounding theircapsids Envelopes are composed pri-marily of the same materials found inthe plasma membranes of all cells Youcan learn about capsids and envelopesin the Focus On on pages 1074ndash1075
The core of nucleic acid contains avirusrsquos genetic material Viral nucleicacid is either DNA or RNA and con-tains instructions for making copies ofthe virus Some viruses have only fourgenes while others have hundredsThe arrangement of proteins in thecapsid of a virus determines the virusrsquosshape Four different viral shapes areshown in Figure 181 The proteinarrangement also plays a role in deter-mining what cell can be infected andhow the virus infects the cell
Attachment to a host cellBefore a virus can replicate it must
enter a host cell Before it can enter itmust first recognize and attach to areceptor site on the plasma membraneof the host cell
A virus recognizes and attaches to ahost cell when one of its proteins inter-locks with a molecular shape that is thereceptor site on the host cellrsquos plasmamembrane A protein in the tail fibersof the bacteriophage T4 shown inFigure 181 recognizes and attachesthe T4 to its bacterial host cell In otherviruses the attachment protein is in thecapsid or in the envelope The recogni-tion and attachment process is like twopieces of a jigsaw puzzle fittingtogether The process might alsoremind you of two spaceships docking
Compare and con-trast the structures of viruses to cells
476 VIRUSES AND BACTERIAOliver MeckeseosGelderblomPhoto Researchers
Measure in SIMeasuring a Virus Can you use a light microscope to view avirus Find out by measuring the size of a polio virus in thephoto below and then comparing it to 02 microm the size limitfor viewing objects with a light microscope
Procedure Copy the data table below
Examine the photo The horizontal line you see wouldmeasure only 04 micrometer (microm) in length if the photowas not magnified 180 000 Use this line for reference
Calculate the diameter of one poliovirus First measurethe length of the reference line in millimeters Record thevalue in the table Then measure the diameter of a polio-virus in millimeters Record the value in the table
$ Use the following equation to calculate the actual diame-ter of the poliovirus (X) Record your answer in the table
photo line length in mm (A)
04 microm
diameter of virus in mm (B) diameter of virus in microm (X)
Analysis1 Interpret Data Explain why you cannot see viruses with a
light microscope Use specific numbers in your answer2 Use Numbers An animal cell may be 100 microm in size How
many polioviruses could fit across the top of such a cell
Data Table
Values to Measure and Calculate Measurement
Length of photo line in mm
Diameter of poliovirus in mm
Diameter of poliovirus in microm
Color-enhanced TEM Magnification 180 000
Reference line
0474-0483 C18S1 BDOL-829900 8404 1218 AM Page 476
477(tl)Dr Linda Stannard UCTScience Photo LibraryPhoto Researchers (tr)Dr Jeremy BurgessScience Photo LibraryPhoto Researchers (bl)Dr Kari LounatmaaScience Photo LibraryPhoto Researchers
(br)Biozentrum University of BaselScience Photo LibraryPhoto Researchers
Attachment is a specific processEach virus has a specifically shaped
attachment protein Therefore eachvirus can usually attach to only a fewkinds of cells For example the T4phage can infect only certain types of
E coli because the T4rsquos attachmentprotein matches a surface molecule ofonly these E coli A T4 cannot infecta human animal or plant cell oreven another bacterium In generalviruses are species specific and some
Capsid
Nucleic acid
Capsid Nucleic acid
Figure 181The different proteins inviral capsids produce a wide variety of viral shapes
Nucleicacid
Envelope
Capsid
An envelope studded with projections covers someviruses including the influenza virus (photo) andthe AIDS-causing virus (inset)
C This T4 virus which infects E coli consists of apolyhedral-shaped head attached to a cylindricaltail with leglike fibers
D
Polyhedral viruses such as the papilloma virusthat causes warts resemble small crystals
A The tobacco mosaic virus has a longnarrow helical shape
B
Capsid
Nucleicacid
Tail fiber
Tail
Color-enhanced TEMMagnification 100 000
Color-enhanced TEMMagnification 76 000
Color-enhanced TEMMagnification 34 000
Color-enhanced TEMMagnification 65 000
0474-0483 C18S1 BDOL-829900 8404 1218 AM Page 477
also are cell-type specific For exam-ple polio viruses normally infect onlyintestinal and nerve cells
The species specific characteristicof viruses is significant for controllingthe spread of viral diseases For exam-ple by 1980 the World HealthOrganization had announced thatsmallpox which is a deadly humanviral disease had been eradicated Theeradication was possible partlybecause the smallpox virus infects onlyhumans A virus such as the one thatcauses the flu is not species specificand infects animals as well as humanstherefore it is difficult to eradicate Avirus such as West Nile virus infectsmainly birds horses and humans
Summarize why avirus can attach to only a few spe-cific host cells
Viral Replication CyclesOnce attached to the plasma
membrane of the host cell the virusenters the cell and takes over itsmetabolism Only then can the virusreplicate Viruses have two ways ofgetting into host cells The virusmay inject its nucleic acid into thehost cell like a syringe injects a vac-cine into your arm as shown inFigure 182 The capsid of the virusstays attached to the outside of thehost cell An enveloped virus entersa host cell in a different way Afterattachment the plasma membraneof the host cell surrounds the virusand produces a virus-filled vacuoleinside the host cellrsquos cytoplasmThen the virus bursts out of thevacuole and releases its nucleic acidinto the cell
478 VIRUSES AND BACTERIA
Attachment Entry
Lysis and Release
Assembly
Replication
Bacteriophage
The bacteriophageinjects its nucleic acidinto the bacterial cell
New virus particles are assembled
The hostlsquos metabolic ma-chinery makes viral nucleic acid and proteins
The host cell breaks open andreleases new virus particles
Nucleicacid
Bacterial DNA
Bacterialhost cell
Figure 182In a lytic cycle a virus usesthe host cellrsquos energy andraw materials to makenew viruses A typical lyticcycle takes about 30 min-utes and produces about200 new viruses
AA BB
CC
DD
EE
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Lytic cycleOnce inside the host cell a virusrsquos
genes are expressed and the sub-stances that are produced take overthe host cellrsquos genetic material Theviral genes alter the host cell to makenew viruses The host cell uses itsown enzymes raw materials andenergy to make copies of viral genesthat along with viral proteins areassembled into new viruses whichburst from the host cell killing itThe new viruses can then infect andkill other host cells This process iscalled a lytic (LIH tik) cycle Followthe typical lytic cycle for a bacterio-phage shown in Figure 182
Lysogenic cycleNot all viruses kill the cells they
infect Some viruses go through alysogenic cycle a replication cycle in which the virusrsquos nucleic acid is
integrated into the host cellrsquos chro-mosome A typical lysogenic cycle fora virus that contains DNA is shown inFigure 183
A lysogenic cycle begins in thesame way as a lytic cycle The virusattaches to the host cellrsquos plasmamembrane and its nucleic acid entersthe cell However in a lysogeniccycle instead of immediately takingover the hostrsquos genetic material theviral DNA is integrated into the hostcellrsquos chromosome
Viral DNA that is integrated intothe host cellrsquos chromosome is called aprovirus A provirus may not affectthe functioning of its host cell whichcontinues to carry out its own meta-bolic activity However every timethe host cell reproduces the provirusis replicated along with the host cellrsquoschromosome Therefore every cellthat originates from an infected host
181 VIRUSES 479
LYTIC CYCLE
LYSOGENIC CYCLE
AA Attachment and EntryProvirus FormationBB
A lysogenic virusinjects its nucleicacid into a bacterium
The viral nucleic acid is calleda provirus when it becomespart of the hostrsquos chromosome
Althoughthe provirusis inactiveit replicatesalong withthe host cellrsquoschromosome
Bacterial hostchromosome
Provirus
The provirus leavesthe chromosome
Viral nucleic acid and proteins are made
The cell breaks openreleasing viruses
CC Cell Division
Figure 183In a lysogenic cycle avirus does not destroythe host cell at onceRather the viral nucleicacid is integrated intothe genetic material ofthe host cell and repli-cates with it for a whilebefore entering a lyticcycle
lytic from theGreek word lyeinmeaning to ldquobreakdownrdquo The hostcell is destroyedduring a lytic cycle
0474-0483 C18S1 BDOL-829900 8404 1219 AM Page 479
Figure 184Before the influenza virus leaves a host cell it is wrapped ina piece of the hostrsquos plasma membrane making an envelopewith the same structure as the hostrsquos plasma membrane
Color-enhanced TEM Magnification 17 150
CNRIScience Photo LibraryPhoto Researchers
cell has a copy of the provirus Thelysogenic phase can continue formany years However at any time theprovirus can be activated and enter alytic cycle Then the virus replicatesand kills the host cell Try to distin-guish the human diseases caused bylysogenic viruses from those caused bylytic viruses in the Problem-Solving Labon this page
Disease symptoms of provirusesThe lysogenic process explains the
reoccurrence of cold sores which arecaused by the herpes simplex I virusEven though a cold sore heals theherpes simplex I virus remains in yourcells as a provirus When the provirusenters a lytic cycle another cold soreerupts No one knows what causes aprovirus to be activated but some sci-entists suspect that physical stresssuch as sunburn and emotional stresssuch as anxiety play a role
Many disease-causing viruses havelysogenic cycles Three examples ofthese viruses are herpes simplex I her-pes simplex II that causes genital her-pes and the hepatitis B virus thatcauses hepatitis B Another lysogenicvirus is the one that causes chickenpox Having chicken pox which usually occurs before age ten giveslifelong protection from anotherinfection by the virus However somechicken pox viruses may remain asproviruses in some of your bodyrsquosnerve cells Later in your life theseproviruses may enter a lytic cycle andcause a disease called shinglesmdashapainful infection of some nerve cells
Release of virusesEither lysis the bursting of a cell or
exocytosis shown in Figure 184 theactive transport process by whichmaterials are expelled from a cellreleases new viruses from the host cell
Characteristics of Some Viral Diseases
Disease Symptom Incubation
Measles Rash fever 9ndash11 days
Shingles Pain itching on skin Years
Warts Bumpy areas on skin Months
Influenza Body aches runny nose fever 1ndash4 days
HIV Fatigue weight loss fever 2ndash5 years
Analyze InformationWhat type of virus causes disease The symptoms andincubation time of a disease can indicate how the virus actsinside its host cell
Solve the ProblemThe table below lists symptoms and incubation times for someviral diseases Use the table to predict which diseases lytic virusesmight cause and which diseases lysogenic viruses might cause
Thinking Critically1 Observe How much time is associated with the replication
cycle of a lytic virus A lysogenic virus2 Describe What diseases may lytic viruses cause Explain
your answer3 Describe What diseases may lysogenic viruses cause
Explain your answer4 Infer What is a possible consequence of the fact that a per-
son infected with HIV may have no symptoms for years
0474-0483 C18S1 BDOL-829900 8404 555 AM Page 480
181 VIRUSES 481
In exocytosis a newly produced virusapproaches the inner surface of thehost cellrsquos plasma membrane Theplasma membrane surrounds the virusenclosing it in a vacuole that then fuseswith the host cellrsquos plasma membraneThen the viruses are released to theoutside
RetrovirusesMany viruses such as the human
immunodeficiency virus (HIV) thatcauses the disease AIDS are RNAvirusesmdashRNA being their onlynucleic acid The RNA virus with themost complex replication cycle is theretrovirus (reh tro VY rus) How canRNA be integrated into a host cellrsquoschromosome which contains DNA
Once inside a host cell the retro-virus makes DNA from its RNA Todo this it uses reverse transcriptase(trans KRIHP tayz) an enzyme it car-ries inside its capsid This enzymehelps produce double-strandedDNA from the viral RNA Then thedouble-stranded viral DNA is inte-grated into the host cellrsquos chromo-some and becomes a provirus Ifreverse transcriptase is found in a
person it is evidence for infection bya retrovirus You can see how a retro-virus replicates in its host cell inFigure 185
Mark E Gibson
Dairy Farmer
D id you grow up on a farm ordo you wish you did Would
you enjoy a chance to work withanimals and be outdoors Perhapsyou should be a dairy farmer
Skills for the JobIn the past most dairy farms were
family owned but now corporationsown some of these farms A person canlearn dairy farming on the job or by completingtwo- and four-year college programs in agriculture Adegree in agriculture can lead to certification as a farmmanager Dairy farmers must keep their herds healthy andproducing both milk and calves Like all farming dairyfarming is a risky business that depends on factors such asthe weather the cost of feed the amount of milk the herdsproduce and the market price for milk and milk products
For more careers in related fields visit
Retrovirus Cycle
Retrovirus
Reversetranscriptase
Enteringcell
Exitingcell
New virusforming
New virus parts
Provirus inhost chromosome
RNA
RNA
mRNA
DNA
DNA is made fromthe viral RNA
Figure 185Retroviruses have anenzyme that transcribestheir RNA into DNA Theviral DNA becomes aprovirus that steadilyproduces small numbersof new viruses withoutimmediately destroyingthe cell Infer How dodoctors often discoverthat someone has aretrovirus infection
cabdolglencoecomcareers
0474-0483 C18S1 BDOL-829900 8404 1220 AM Page 481
HIV An infection of white blood cells
Once inside a human host HIVinfects white blood cells Newly madeviruses are released into the bloodstream by exocytosis and infect otherwhite blood cells Infected host cellsstill function normally because theviral genetic material is a provirusthat produces only a small number ofnew viruses at a time Because theinfected cells are still able to functionnormally an infected person may notappear sick but they can still transmitthe virus in their body fluids
An HIV-infected person can expe-rience no AIDS symptoms for a longtime However most people with anHIV infection eventually get AIDSbecause over time more white bloodcells are infected and produce newviruses Figure 186 People gradu-ally lose white blood cells becauseproviruses enter a lytic cycle and killtheir host cells Because white bloodcells are part of a bodyrsquos disease-fighting system their destructioninterferes with the bodyrsquos ability toprotect itself from organisms thatcause disease a symptom of AIDS
Cancer and VirusesSome viruses have been linked to
certain cancers in humans and ani-mals For example the hepatitis Bvirus has been shown to play a role incausing liver cancer These virusesdisrupt the normal growth and divi-sion of cells in a host causing abnor-mal growth and creating tumors
Prions and viroidsResearchers have recently discov-
ered some particles that behave some-what like viruses and cause infectiousdiseases Prions are composed of proteins but have no nucleic acid tocarry genetic information Prions arethought to act by causing other pro-teins to fold themselves incorrectlyresulting in improper functioningPrions are responsible for many animaldiseases such as mad cow disease andits human equivalent Creutzfeldt-Jakob disease
Viroids are composed of a singlecircular strand of RNA with no proteincoat Viroids have been shown to causeinfectious diseases in several plantsThe amount of viroid RNA is muchless than the amount found in viruses
(l)Andrew SyredScience Photo LibraryPhoto Researchers (r)NIBSCScience Photo LibraryPhoto Researchers
AA
BBColor-enhanced
SEMMagnification
6000
Color-enhanced SEM Magnification 3500
Figure 186Normal white blood cells are an essential partof a humanrsquos immune system (A) In an HIV-infected person white blood cells are eventu-ally destroyed by HIV proviruses (shown asred objects) that enter lytic cycles (B)
482 VIRUSES AND BACTERIA
0474-0483 C18S1 BDOL-829900 8404 1222 AM Page 482
Understanding Main Ideas1 Why is a virus considered to be nonliving2 What is the difference between a lytic cycle and
a lysogenic cycle3 What is a provirus4 How do retroviruses convert their RNA to DNA
Thinking Critically5 Describe the state of a herpes virus in a person
who had cold sores several years ago but whodoes not have them now
6 Make and Use Graphs A microbiologist addedsome viruses to a bacterial culture Every hourfrom noon to 400 PM she determined the num-ber of viruses present in a sample of the cultureHer data were 3 3 126 585 and 602 Graphthese results How would the graph look if theculture had initially contained dead bacteria Formore help refer to Make and Use Graphs in theSkill Handbook
SKILL REVIEWSKILL REVIEW
181 VIRUSES 483(l)Jack M BostrackVisuals Unlimited (r)WaysideVisuals Unlimited
Figure 187Tobacco mosaic viruscauses yellow spots ontobacco leaves makingthem unmarketable (A)In contrast another viruscauses the beautifulstripes of Rembrandttulips making them moredesirable (B)
AA BB
Plant virusesThe first virus to be identified was a
plant virus called tobacco mosaic virusthat causes disease in tobacco plantsThere are more than 400 viruses that infect a variety of plants Theseviruses cause as many as 1000 plantdiseases and are named according totheir host plant Viruses can causestunted growth and yield losses intheir host plants Plant viruses requirewounds or insect bites to enter andinfect a host and do not use surfacerecognition They do not undergolytic or lysogenic phases
Not all viral plant diseases are fatalor even harmful Some mosaicviruses cause striking patterns ofcolor in the flowers of plants Theinfected flowers like the ones shown
in Figure 187B have streaks ofvibrant contrasting colors in theirpetals These viruses are easily spreadamong plants when you cut aninfected stem and then cut healthystems with the same tool
Origin of VirusesYou might assume that viruses rep-
resent an ancestral form of lifebecause of their relatively uncompli-cated structure This is probably notso For replication viruses need hostcells therefore scientists suggest thatviruses might have originated fromtheir host cells Some scientists sug-gest that viruses are nucleic acids thatbreak free from their host cells whilemaintaining an ability to replicateparasitically within the host cells
cabdolglencoecomself_check_quiz
0474-0483 C18S1 BDOL-829900 8404 1222 AM Page 483
182
Diversity of ProkaryotesRecall that prokaryotes are unicellular organisms that do not have a
nucleus or membrane-bound organelles They are classified in two king-domsmdasharchaebacteria and eubacteria Many biochemical differencesexist between these two types of prokaryotes For example their cell wallsand the lipids in their plasma membranes differ In addition the structureand function of the genes of archaebacteria are more similar to those ofeukaryotes than to those of eubacteria
Because they are so different many scientists propose that archaebacte-ria and eubacteria arose from a common ancestor several billion years ago
Archaebacteria The extremistsThere are three types of archaebacteria that live mainly in extreme
habitats where there is usually no free oxygen available You can see someof these environments in Figure 188 One type of archaebacterium lives
SECTION PREVIEWObjectivesCompare the types ofprokaryotesExplain the characteristicsand adaptations of bacteriaEvaluate the economicimportance of bacteria
Review Vocabularyprokaryote unicellular
organism whose celllacks a nucleus andinternal membrane-bound organelles (p 173)
New Vocabularychemosynthesisbinary fissionconjugationobligate aerobeobligate anaerobeendosporetoxinnitrogen fixation
Viruses and Bacteria Make the following Foldable to help you organize information about viruses and bacteria
Virus Bacteria
Structure
Replication
Kinds
Harmful
Beneficial
Fold one piece of paper lengthwise into thirds
Fold the paper widthwise into six sections
Unfold lay the paper verticallyand draw lines along the folds
Label your table as shown
STEP 1
STEP 3
STEP 2
STEP 4
484 VIRUSES AND BACTERIA
Archaebacteria and Eubacteria
Compare and Contrast As you read Section 182 complete the table by describing the characteristics of viruses and bacteria
Standard 1c Students know how prokaryotic cells eukaryotic cells(including those from plants and animals) and viruses differ in complexity and general structure
California Standards
0484-0501 C18S2 BDOL-829900 8404 616 AM Page 484
BDOL-182
null
96869934
in oxygen-free environments and pro-duces methane gas These methane-producing archaebacteria live inmarshes lake sediments and thedigestive tracts of some mammalssuch as cows They also are found atsewage disposal plants where theyplay a role in the breakdown ofsewage
A second type of archaebacteriumlives only in water with high concen-trations of salt such as in UtahrsquosGreat Salt Lake and the Middle EastrsquosDead Sea A third type lives in thehot acidic waters of sulfur springs
This type of anaerobic archaebac-terium also thrives near cracks deep inthe ocean floor where it is theautotrophic producer for a uniqueanimal communityrsquos food chain
Eubacteria The heterotrophsEubacteria the other kingdom of
prokaryotes includes those prokary-otes that live in places more hos-pitable than archaebacteria inhabitand that vary in nutritional needsThe heterotrophic eubacteria livealmost everywhere and use organicmolecules as their food source
182 ARCHAEBACTERIA AND EUBACTERIA 485(t)Fritz PolkingVisuals Unlimited (bl)Emory KristofNational Geographic Society Image Collection (br)Kaj R SvenssonScience Photo LibraryPhoto Researchers
Figure 188Archaebacteria live in extreme environments
Heat- and acid-loving archaebacteria live around deep oceanvents where water temperatures are often above 100degC
C
Methane-producing archaebacteriaflourish in this swamp and also live inthe stomachs of cows
A
Salt-loving archaebacteria live in thesesalt pools left after this lake in BritishColumbia Canada evaporated Thesepools have high levels of magnesiumand potassium salts
B
0484-0501 C18S2 BDOL-829900 8304 1138 PM Page 485
Some bacterial heterotrophs areparasites obtaining their nutrientsfrom living organisms They are notadapted for trapping food that con-tains organic molecules or for mak-ing organic molecules themselvesOthers are saprophytesmdashorganismsthat feed on dead organisms ororganic wastes Recall that sapro-phytes break down and recycle thenutrients locked in the body tissuesof dead organisms
Eubacteria Photosynthetic autotrophs
A second type of eubacterium is thephotosynthetic autotroph Theseeubacteria live in places with sunlightbecause they need light to make theorganic molecules that are their foodCyanobacteria are photosyntheticautotrophs They contain the pig-ment chlorophyll that traps the sunrsquosenergy which they then use in photo-synthesis Most cyanobacteria likethe Anabaena shown in Figure 189
are blue-green and some are red oryellow in color Cyanobacteria com-monly live in ponds streams andmoist areas of land They are com-posed of chains of independent cells
Eubacteria Chemosynthetic autotrophs
A third type of eubacterium is thechemosynthetic autotroph Like pho-tosynthetic bacteria these bacteriamake organic molecules that are theirfood However unlike the photosyn-thetic bacteria the chemosyntheticbacteria do not obtain the energy theyneed to make food from sunlightInstead they break down and releasethe energy of inorganic compoundscontaining sulfur and nitrogen in the process called chemosynthesis(kee moh SIHN thuh sus) Somechemosynthetic bacteria are veryimportant to other organisms becausethey are able to convert atmosphericnitrogen into the nitrogen-containingcompounds that plants need
What is a bacteriumA bacterium consists of a very
small cell Although tiny a bacterialcell has all the structures necessaryto carry out its life functions
The structure of bacteriaProkaryotic cells have ribosomes
but their ribosomes are smaller thanthose of eukaryotes They also havegenes that are located for the mostpart in a single circular chromosomerather than in paired chromosomesWhat structures can protect a bac-terium Look at Figure 1810 on thenext page to learn about other struc-tures located in bacterial cells
One structure that supports andprotects a bacterium is the cell wallThe cell wall protects the bacteriumby preventing it from bursting
486 VIRUSES AND BACTERIA
cyanobacteriumfrom the Greekwords kyanosmeaning ldquobluerdquoand bakterionmeaning ldquosmallrodrdquo The cyano-bacteria are blue-green bacteria
Michael AbbeyPhoto Researchers
Figure 189Cyanobacteria such asAnabaena are photo-synthetic and have ablue-green color
LM Magnification 250
0484-0501 C18S2 BDOL-829900 8304 1138 PM Page 486
A Typical Bacterial CellFigure 1810Bacteria are microscopic prokaryotic cells Bacteriaare unicellular A typical bacterium such as Escherichiacoli shown at the right would have some or all of thestructures shown in this diagram of a bacterial cellCritical Thinking Which structures of bacteria areinvolved in reproduction
182 ARCHAEBACTERIA AND EUBACTERIA 487
Flagellum Somebacteria have longwhiplike protrusionscalled flagella (singularflagellum) that enablethem to move
DD
Pilus Some bacteria have pilimdashhairlikestructures emerging from the cell surface Ahairlike pilus helps a bacterium stick to asurface By helping them stick to oneanother pili help bacteria exchange DNA
FF
Plasma membraneA plasma membranesurrounds the cell andregulates what entersand leaves the cell
GG
Chromosome A single DNAmolecule arranged as a circularchromosome and not enclosedin a nucleus contains most ofthe bacteriumrsquos genes
CC
Plasmid A few genes arelocated in a small circularchromosome piece called aplasmid A bacterium mayhave one or more plasmids
EE
Cell wall A cell wallsurrounds the plasmamembrane It gives thecell its shape andprevents osmosis frombursting the cell
BB
Capsule Some bacteria have asticky gelatinous capsule around thecell wall A bacterium with a capsuleis more likely to cause disease than abacterium without a capsule
AA
Escherichia coli
Color-enhanced TEM Magnification 3000
Dr Linda Stannard UCTScience Photo LibraryPhoto Researchers
0484-0501 C18S2 BDOL-829900 8304 1139 PM Page 487
Because most bacteria live in a hypo-tonic environment one in whichthere is a higher concentration ofwater molecules outside than insidethe cell water is always trying toenter a bacterial cell A bacterial cellremains intact however and doesnot burst open as long as its cell wallis intact If the cell wall is damagedwater will enter the cell by osmosiscausing the cell to burst Scientistsused a bacteriumrsquos need for an intactcell wall to develop a weapon againstbacteria that cause disease
In 1928 Sir Alexander Flemingaccidentally discovered penicillin thefirst antibioticmdasha substance thatdestroys bacteriamdashused in humansHe was growing bacteria when an air-borne mold Penicillium notatum con-taminated his culture plates Henoticed that the mold shown inFigure 1811 secreted a substancemdashnow known as the antibiotic peni-cillinmdashthat killed the bacteria he wasgrowing Later biologists discoveredthat penicillin can interfere with the
ability of some bacteria to make cellwalls When such bacteria grow inpenicillin holes develop in their cellwalls water enters their cells andthey rupture and die
Identifying bacteriaScientists have developed ways to
distinguish among bacteria Forexample one trait that helps catego-rize bacteria is how they react toGram stain Gram staining is a tech-nique that distinguishes two groups ofbacteria because the stain reflects abasic difference in the composition ofbacterial cell walls The cell walls ofall bacteria are made of interlinkedsugar and amino acid molecules thatdiffer in arrangement and react differ-ently to Gram stain After stainingGram-positive bacteria are purpleand Gram-negative bacteria are pinkGram-positive bacteria are affectedby different antibiotics than thosethat affect Gram-negative bacteria
Not only do bacterial cell wallsreact differently to Gram stain butthey also give bacteria differentshapes Shape is another way to cate-gorize bacteria The three most com-mon shapes are spheres called cocci rods called bacilli and spiralscalled spirilla An example of eachshape is shown in Figure 1812 Inaddition to having one of theseshapes bacterial cells often grow incharacteristic patterns that provideanother way of categorizing themDiplo- is a prefix that refers to a pairedarrangement of cell growth The pre-fix staphylo- describes an arrangementof cells that resemble grapes Strepto-is a prefix that refers to an arrange-ment of chains of cells
Describe whatshape and growth pattern youwould expect Staphylococcusbacteria to have
488 VIRUSES AND BACTERIAArthur M SiegelmanVisuals Unlimited
Figure 1811The mold known asPenicillium notatumshown above in itsgrowth stages producesthe antibiotic penicillin
0484-0501 C18S2 BDOL-829900 8304 1140 PM Page 488
Reproduction by binary fissionBacteria cannot reproduce by
mitosis or meiosis because they haveno nucleus and instead of pairs ofchromosomes they have one circularchromosome and varying numbers ofsmaller circular pieces of DNA calledplasmids Therefore they have otherways to reproduce
Bacteria reproduce asexually by aprocess known as binary fission Toreproduce in this way a bacteriumfirst copies its chromosome Then theoriginal chromosome and the copybecome attached to the cellrsquos plasmamembrane for a while The cell growslarger and eventually the two chro-mosomes separate and move to oppo-site ends of the cell Then a partitionforms between the chromosomes asshown in Figure 1813 This parti-tion separates the cell into two simi-lar cells Because each new cell haseither the original or the copy of the
chromosome the resulting cells aregenetically identical
Bacterial reproduction can berapid In fact under ideal conditionssome bacteria can reproduce every 20minutes producing enormous num-bers of bacteria quickly If bacteriaalways reproduced this fast theywould cover the surface of Earthwithin a few weeks But bacteria donrsquotalways have ideal growing conditionsThey run out of nutrients and water
(tl)D
avid
MP
hilli
psV
isua
ls U
nlim
ited
(tc
)Sco
tt C
amaz
ine
Pho
to R
esea
rche
rs
(tr)
Mik
e P
eres
Cus
tom
Med
ical
Sto
ck P
hoto
(b
)AB
Dow
sett
Sci
ence
Pho
to L
ibra
ryP
hoto
Res
earc
hers
Figure 1812Bacteria exist in threemain shapes
Figure 1813This Escherichia coli cell is starting to divideThe newly forming partition is visible in thecenter of the cell
These spherical Gram-positiveStreptococcus pneumoniaebacteria cause pneumonia
A
Color-enhanced SEM Magnification 34 000
This rodlike Gram-positive bacter-ium Bacillus anthracis commonly exists in the soil It can cause anthraxin cattle sheep and humans
B
Color-enhanced SEM Magnification unavailable
This spiral-shaped Gram-negativeSpirillum volutans bacterium hasflagella
C
LM Magnification 250
Color-enhanced TEM Magnification 16 500
0484-0501 C18S2 BDOL-829900 8304 1140 PM Page 489
they poison themselves with theirown wastes and predators eat them
Sexual reproductionIn addition to binary fission some
bacteria have a form of sexual repro-duction called conjugation Duringconjugation (kahn juh GAY shun) onebacterium transfers all or part of itschromosome to another cell throughor on a bridgelike structure called apilus (plural pili) that connects the twocells In Figure 1814 you can see howthis genetic transfer occurs Conjuga-tion results in a bacterium with a newgenetic composition This bacteriumcan then undergo binary fission pro-ducing more cells with the samegenetic makeup
Try the MiniLab on this page to seesome bacterial staining reactions cellshapes and patterns of growth
Adaptations in BacteriaBased on fossil evidence some scien-
tists propose that anaerobic bacteriawere probably among the first photo-synthetic organisms producing notonly their own food but also oxygen Asthe concentration of oxygen increased
490 VIRUSES AND BACTERIA(t)Oliver MeckesPhoto Researchers (b)Dr L CaroScience Photo LibraryPhoto Researchers
Figure 1814The E coli at the bottom is attachedto the other bacteria by pili throughor on which genetic material is beingtransferred Infer How would con-jugation be a useful addition tobinary fission
Color-enhanced TEM Magnification 5000
ObserveBacteria Have DifferentShapes Bacteria come inthree shapes spherical (coccus) rodlike (bacillus)and spiral shaped (spiril-lum) They may appearsingly or in pairs chains orclusters Each species has atypical shape and reaction toGram stain
Procedure Obtain slides of bacteria from your teacher Using low power locate bacteria of one shape Switch to
high power Look for individual cells and observe theirshape Also observe the size of the cells and their colorThen look for groups of bacterial cells to determine theirarrangement CAUTION Use caution when working with a microscope and microscope slides
Repeat step 2 for bacteria with the other shapes Thencompare the sizes of the bacteria
$ Draw a diagram of each type of bacteria
Analysis1 Measure How do the sizes of the three bacteria compare2 Classify Which of the bacteria were Gram negative3 Explain What adaptive advantage might there be for
bacteria to form groups of cells
Staphylococcus bacteria
Color-enhanced SEM Magnification 50 000
0484-0501 C18S2 BDOL-829900 8304 1140 PM Page 490
in Earthrsquos atmosphere some bacteriaprobably adapted over time to useoxygen for respiration
Diversity of metabolismRecall that breaking down food to
release its energy is called cellular res-piration Modern bacteria havediverse types of respiration
Many bacteria require oxygen forrespiration These bacteria are calledobligate aerobes Mycobacteriumtuberculosis the organism that causesthe lung disease called tuberculosisis an obligate aerobe There areother bacteria called obligateanaerobes that are killed by oxy-gen Among bacteria that are obli-gate anaerobes is the bacteriumTreponema pallidum that causes syph-ilis a sexually transmitted diseaseand the bacterium that causes botu-lism a type of food poisoning thatyou will learn more about soonThere are still other bacteria that canlive either with or without oxygenreleasing the energy in food aerobi-cally by cellular respiration or anaer-obically by fermentation
A survival mechanismSome bacteria when faced with
unfavorable environmental condi-tions produce endospores shown inFigure 1815 An endospore is a tinystructure that contains a bacteriumrsquosDNA and a small amount of its cyto-plasm encased by a tough outer cov-ering that resists drying outtemperature extremes and harshchemicals As an endospore the bac-terium rests and does not reproduceWhen environmental conditionsimprove the endospore germinatesor produces a cell that begins to growand reproduce Some endosporeshave germinated after thousands ofyears in the resting state
Although endospores are useful tobacteria they can cause problems forpeople Endospores can survive a tem-perature of 100degC which is the boilingpoint of water To kill endosporesitems must be sterilizedmdashheated underhigh pressure in either a pressurecooker or an autoclave Under pres-sure water will boil at a higher temper-ature than its usual 100degC and thishigher temperature kills endospores
182 ARCHAEBACTERIA AND EUBACTERIA 491AB DowsettScience Photo LibraryPhoto Researchers
Figure 1815This TEM magnificationshows bacteria in threedifferent stages ofendospore production
Color-enhanced TEM Magnification 12 500
0484-0501 C18S2 BDOL-829900 8404 616 AM Page 491
Canned foods must be sterilizedand acidified This is because theendopores of the bacterium calledClostridium botulinum easily get intofoods being canned These bacteriabelong to the group clostridiamdashallobligate anaerobic bacteria that form endospores If the endospores ofC botulinum get into improperly ster-ilized canned food they germinateBacteria grow in the anaerobic envi-ronment of the can and produce apowerful and deadly poison called atoxin as they grow This deadly toxinsaturates the food and if eaten causesthe disease called botulism Althoughrare botulism is often fatal and it canbe transmitted in many ways otherthan poorly canned food as shown inFigure 1816 Try the Problem-Solving Lab on this page to learn moreabout C botulinum
A different bacterium Bacillusanthracis lives in the soil B anthraciscauses anthrax a disease that com-monly infects cattle and sheep butcan also infect humans Most humananthrax infections are fairly harmlessand occur on the skin as a result ofhandling animals The bacterialspores can become airborne howeverand if inhaled in large amounts can
492 VIRUSES AND BACTERIA
HypothesizeCan you get food poison-ing from eating home-canned foods Clostridiumbotulinum is a bacterialspecies that causes food poisoning
Solve the ProblemC botulinum is an obligateanaerobic soil bacterium andit easily spreads onto plantsIt forms endospores that arehighly heat-resistant and germinate only in anaerobicconditions The bacteriumproduces a heat-resistant toxin that can kill humansCommercially canned foods are heated to 121degC for a mini-mum of 20 minutes to ensure that all spores are killed
Thinking Critically1 Hypothesize Why donrsquot you get food poisoning if you
eat fresh vegetables that are contaminated with the endo-spores of C botulinum
2 Hypothesize How do the endospores of C botulinum getinto home-canned vegetables
3 Hypothesize How can C botulinum endospores surviveinadequate home-canning procedures
4 Explain Why do endospores of C botulinum germinateinside canning jars
(t)Larry LefeverGrant Heilman Photography (b)KS Studios
Figure 1816CAUTION When a foil-wrappedpotato is baked any Clostridiumbotulinum spores on its skin cansurvive If the potato is eaten imme-diately the spores cannot germi-nate However if the still-wrappedpotato cools at room temperaturethe spores can germinate in theanaerobic environment of the foiland the bacteria will produce theirdeadly toxin
0484-0501 C18S2 BDOL-829900 8304 1141 PM Page 492
germinate in a personrsquos lungs causingan infection This infection is moreserious than a skin infection and oftenfatal The infection harms the lungs byproducing toxins that damage lung tis-sue and the circulatory system Becauseanthrax can be easily spread throughthe air it has been used to intentionallyharm people as a biological weapon
The Importance of Bacteria
When you think about bacteriayour first thought may be disease Butdisease-causing bacteria are few com-pared with the number of harmlessand beneficial bacteria on EarthBacteria help to fertilize fields torecycle nutrients on Earth and toproduce foods and medicines
Nitrogen fixationMost of the nitrogen on Earth
exists in the form of nitrogen gas N2which makes up about 80 percent of
the atmosphere All organisms neednitrogen because the element is acomponent of their proteins DNARNA and ATP Yet few organismsincluding most plants can directlyuse nitrogen from the air
Several species of bacteria haveenzymes that convert N2 into ammo-nia (NH3) in a process known asnitrogen fixation Other bacteriathen convert the ammonia into nitrite(NO2
) and nitrate (NO3) which
plants can use Bacteria are the onlyorganisms that can perform thesechemical changes
Some nitrogen-fixing bacteria livesymbiotically within the roots ofsome trees and legumesmdashplants suchas peas peanuts and soybeansmdashinswollen areas called nodules You cansee some nodules in Figure 1817Farmers grow legume crops after theharvesting of crops such as cornwhich depletes the soil of nitrogenNot only do legumes replenish thesoilrsquos nitrogen supply they are an eco-nomically useful crop
182 ARCHAEBACTERIA AND EUBACTERIA 493(l)David M DennisTom Stack amp Associates (c)Grant HeilmanGrant Heilman Photography (r)G Shih amp R KesselVisuals Unlimited
Figure 1817Soybean plants haveswellings called noduleson their roots (A) Thenodules (B) contain bacte-ria called Rhizobium (C)that convert nitrogen gasinto ammonia In thissymbiotic association theplant gains usable nitro-gen and the bacteriagain food
Color-enhanced SEMMagnification 7400
AA
BB
CC
PhysicalScience
Connection
Classify everydaymatter Elementsare substances withthe same numberof protons in thenucleus of theiratoms Forexample allnitrogen atoms (N)in nitrogen gas (N2)have 7 protonsCompounds suchas ammonia (NH3)consist of morethan one elementpresent in fixedproportions Theratio of nitrogen tohydrogen atoms inammonia always is1 to 3
0484-0501 C18S2 BDOL-829900 8304 1141 PM Page 493
494 VIRUSES AND BACTERIA
Recycling of nutrientsYou learned that life could not exist
if decomposing bacteria did not breakdown the organic materials in deadorganisms and wastes returningnutrients both organic materials andinorganic materials to the environ-ment Autotrophic bacteria and alsoplants and algae which are at the bot-tom of the food chains use the nutri-ents in the food they make
This food is passed from one het-erotroph to the next in food chainsand webs In the process of makingfood many autotrophs replenish thesupply of oxygen in the atmosphereYou can see from all this that otherlife depends on bacteria
Food and medicinesSome foods that you eatmdashmellow
Swiss cheese shown in Figure 1818crispy pickles tangy yogurtmdashwouldnot exist without bacteria During
respiration different bacteria pro-duce diverse products many of whichhave distinctive flavors and aromasAs a result specific bacteria are usedto make different foods such as vine-gar cheeses and sauerkraut Bacteriaalso inhabit your intestines and pro-duce vitamins and enzymes that helpdigest food
In addition to food some bacteriaproduce important antibiotics thatdestroy other types of bacteria Strep-tomycin erythromycin bacitracinand neomycin are some of theseantibiotics How do you know whichantibiotic you need when you aresick The BioLab at the end of thischapter will help you learn how scien-tists have obtained such information
Bacteria cause diseaseBacteria cause diseases in plants and
animals causing crops and livestocklosses that impact humans indirectly
(l)Kunio OwakiThe Stock Market (c)Steve NeedhamEnvision (r)UFCSIMVisuals Unlimited
AA
BB
CCFigure 1818Bacteria not only give Swiss cheese (A)its flavor but also its holes as they produce carbon dioxide that bubblesthrough the cheese (B) Useful bacteria are grown in large industrial fermenting vats (C)
0484-0501 C18S2 BDOL-829900 8304 1142 PM Page 494
Understanding Main Ideas1 Describe six parts of a typical bacterial cell State
the function of each2 What are endospores How do they help bacteria
survive3 Explain how penicillin affects a bacterial cell4 Explain how bacteria avoid osmotic rupture
Thinking Critically5 Some scientists have proposed that bacterialike
cells were probably among the earliest organisms
to live on Earth Draw up a list of reasons whysuch a suggestion is feasible Then explain eachreason on your list
6 Make and Use Tables Construct a table compar-ing and contrasting archaebacteria and eubacte-ria Include at least three ways they are alike andthree ways they are different For more help referto Make and Use Tables in the Skill Handbook
SKILL REVIEWSKILL REVIEW
182 ARCHAEBACTERIA AND EUBACTERIA 495
Table 181 Diseases Caused by Bacteria
Disease Transmission Symptoms Treatment
Strep throat Inhale or Fever sore throat Antibiotic(Streptococcus) ingest through swollen neck glands
mouthTuberculosis Inhale Fatigue fever night Antibiotic
sweats cough weightloss chest pain
Tetanus Puncture Stiff jaw muscle Open and clean woundwound spasms paralysis antibiotic give antitoxin
Lyme disease Bite of Rash at site of bite Antibioticinfected tick chills body aches
joint swellingDental Bacteria in Destruction of tooth Remove and fill thecavities (caries) mouth enamel toothache destroyed area of toothDiphtheria Inhale or Sore throat fever Vaccination to prevent
close contact heart or breathing antibioticsfailure
Bacteria also cause many human dis-eases some of which you can seelisted in Table 181 Disease-causingbacteria can enter human bodiesthrough openings such as the mouthThey are carried in air food andwater and sometimes invade humansthrough skin wounds Bacterial dis-eases harm people in two ways Thegrowth of the bacteria can interferewith the normal function of body tis-sue or it can release a toxin thatdirectly attacks the host
In the past bacterial illnesses hada greater effect on human popula-tions than they do now As recentlyas 1900 life expectancy in the
United States was only 47 yearsThe most dangerous diseases at thattime were the bacterial illnessestuberculosis and pneumonia In thelast 100 years human life expectancyhas increased to about 75 years Thisincrease is due to many factorsincluding better public health sys-tems improved water and sewagetreatment better nutrition and bet-ter medical care These improve-ments along with antibiotics havereduced the death rates from bacter-ial diseases to low levels Howeverthis is starting to change as you canread in the Biology and Society featureat the end of this chapter
cabdolglencoecomself_check_quiz
0484-0501 C18S2 BDOL-829900 8304 1142 PM Page 495
Before YouBegin
Doctors must know whichantibiotic kills each typeof disease-causing bac-terium You can use a testsimilar to the one in thisBioLab to discover thisinformation You will usesterile agar-containingpetri dishes and sterileantibiotic disks When youplace a disk on the agarthe antibiotic diffuses intothe agar A clear ring thatdevelops around a diskmdashazone of inhibitionmdashiswhere the antibiotic killedsusceptible bacteria
How sensitive are bacteriato antibiotics
ProblemHow can you determine which antibiotic most effectivelykills specific bacteria
HypothesesDecide on one hypothesis that you will test Your hypothesismight be that the antibiotic with the widest zone of inhibi-tion most effectively inhibits growth of that bacteria
ObjectivesIn this BioLab you will Compare how effectively different antibiotics kill specific
bacteria Determine the most effective antibiotic to treat an infec-
tion that these bacteria might cause
Possible Materialscultures of bacteria marking pensterile nutrient agar long-handled cotton swabs
petri dishes forcepsantibiotic disks 37degC incubatorsterile disks of blank metric ruler
filter paper
Safety PrecautionsCAUTION Always wear goggles in the lab Although the bac-teria you will work with are not disease-causing do not spillthem Wash your hands with antibacterial soap immediatelyafter handling any bacterial culture Clean your work areaafter you finish Follow your teacherrsquos instructions aboutdisposal of your swabs cultures and petri dishes
Skill HandbookIf you need help with this lab refer to the Skill Handbook
PREPARATIONPREPARATION
Matt Meadows
0484-0501 C18S2 BDOL-829900 8304 1144 PM Page 496
182 ARCHAEBACTERIA AND EUBACTERIA 497
1 Examine the materials provided by your teacher and study the photos inthis lab As a group agree on one way that your group could investigateyour hypothesis Design an experiment in which you can collect quantita-tive data
2 Make a list of numbered directions and include the amounts of each mate-rial you will need If possible use no more than one petri dish for eachperson
3 Design and construct a table for recording data To do this carefully con-sider what data you need to record and how you will measure the data Forexample how will you measure what happens around the antibiotic disks asthe antibiotic diffuses into the agar
Check the PlanDiscuss the following points with other group members1 How will you set up your petri dishes How many antibiotics
can you test on one petri dish How will you measure theeffectiveness of each antibiotic What will be your control
2 Will you add the bacteria or the antibiotic disks first3 What will you do to prevent other bacteria from contaminat-
ing the petri dishes4 How often will you observe the petri dishes5 Make sure your teacher has approved your experimental
plan before you proceed further6 Carry out your experiment CAUTION Wash your hands with antibacterial
soap and water after handling dishes of bacteria7 Consult with your teacher in order to make wise
choices in the disposal of bacterial cultures and antibiotics CLEANUP AND DISPOSAL
PLAN THE EXPERIMENTPLAN THE EXPERIMENT
ANALYZE AND CONCLUDEANALYZE AND CONCLUDE
1 Measure in SI How did you measure the zones of inhibition Why did you do it thisway
2 Draw Conclusions Suppose you were aphysician treating a patient infected withthese bacteria Which antibiotic would youuse Why
3 Analyze the Procedure What limitationsdoes this technique have If these bacteria wereinfecting a person what other tests mightincrease your confidence about treating theperson with the most effective antibiotic
Application Use a similar procedure to testthe effectiveness of four commercial antibac-terial soaps and evaluate their promotionalclaims Check your plan with your teacherthen prepare your disks by soaking them inthe different soap solutions
Web Links To find out more about antibiotics visitcabdolglencoecomantibiotics
Matt Meadows
0484-0501 C18S2 BDOL-829900 8404 1209 AM Page 497
Antibiotics have prevented millions of deaths from bacterial diseases in the past century
Today however many disease-causing bacteriahave developed resistance to the antibiotics that used to kill them The spread of antibiotic-resistant bacteria carries with it the threat ofincurable disease Microbiologists are working to develop new drugs to defeat these ldquosuperbugsrdquo
Perspectives During the past 50 years antibi-otics have been used for preventive medical rea-sons and in agriculture With the developmentof resistant bacteria these uses are beingreassessed
How much is too much Because antibioticshave worked well and had few side effects somephysicians prescribe them for preventive reasonsFor example physicians may prescribe antibioticsbefore surgery to prevent the chance of infectionfrom bacteria during the surgery In additionsome physicians prescribe antibiotics for patientswith viral infections because a viral infectionmakes a body vulnerable to a bacterial infection
Because antibiotics hasten the growth of heal-thy cattle chickens and other domestic animalsmany animal feeds contain small amounts ofantibiotics Similarly antibiotics are used to coatfruit and other agricultural products These anti-biotics may produce resistant bacteria whichpass to people when they eat the food
Emerging resistance Many antibiotics areavailable and several bacteria that they oncekilled are now resistant to one or more of them
Superbugs Defy Drugs
KS Studios
498 VIRUSES AND BACTERIA
Tuberculosis for example is a deadly highlycontagious disease that a combination of antibi-otics usually treats effectively But strains ofresistant tuberculosis bacteria have appearedand the disease continues to claim lives afteronce being targeted for elimination throughantibiotic use
Some Staphylococcus bacteria which cause seri-ous infections in hospital patients were previouslyresistant to all antibiotics except vancomycin anantibiotic usually reserved as a last-resort anti-biotic Now vancomycin resistance has turned upin another common ldquohospital bugrdquo EnterococcusResistance genes spread easily among bacteria andvancomycin-resistant staphylococcus infectionshave recently appeared
Developing better antibiotics Microbiologistsare experimenting with bacterial viruses or bacte-riophages to develop new antibiotics Bacterio-phages commonly called phages prevent bacteriafrom building outer cell walls weakening andkilling the bacteria Researchers believe phageDNA can be used to produce antibiotics thatwould attack bacterial cell walls When bacterialstrains develop resistance the phagersquos DNA codecould be manipulated to create an antibiotic thatattacks a different point in the cell wall
Genetics may provide another weapon in thefight against disease One bacterium Streptomycescoelicolor is used to produce several antibioticsThe recent sequencing of its genome could leadto new antibiotics as researchers mix and matchthe genes to produce new compounds and medicines
Prescription antibiotics
Think Critically Not all bacteria are harmful Howmight microbiologists use genetics to target specific disease-causing bacteria with new antibiotics
To find out more about bacteria that are antibiotic-resistant visit cabdolglencoecombiology_society
0484-0501 C18S2 BDOL-829900 8404 617 AM Page 498
Section 181Key Concepts Viruses are nonliving particles that have a
nucleic acid core and a protein-containingcapsid
To replicate a virus must first recognize ahost cell then attach to it and finally enterthe host cell and take over its metabolism
During a lytic cycle a virus replicates andkills the host cell In a lysogenic cycle avirusrsquos DNA is integrated into a chromo-some of the host cell but the host cell doesnot die
Retroviruses contain RNA Reverse tran-scriptase is an enzyme that helps convertviral RNA to DNA which is then inte-grated into the host cellrsquos chromosome
Prions and viroids are virus-like particlesPrions are composed of only a proteinwhile a viroid is a singular strand of RNA
Viruses probably originated from theirhost cells
Vocabularybacteriophage (p 475)capsid (p 476)host cell (p 475)lysogenic cycle (p 479)lytic cycle (p 479)prion (p 482)provirus (p 479)retrovirus (p 481)reverse transcriptase
(p 481)viroid (p 482)virus (p 475)
Viruses
Key Concepts There are two kingdoms of prokaryotes
archaebacteria and eubacteria Archae-bacteria inhabit extreme environmentsEubacteria live almost everywhere elseThey probably arose separately from acommon ancestor billions of years ago
Bacteria are varied Some are heterotrophssome are photosynthetic autotrophs andothers are chemosynthetic autotrophsBacteria can be obligate aerobes obligateanaerobes or both aerobic and anaerobic
Bacteria usually reproduce by binary fis-sion Some have a type of sexual reproduc-tion called conjugation Some bacteriaform endospores that enable them to sur-vive when conditions are unfavorable
Vocabularybinary fission (p 489)chemosynthesis (p 486)conjugation (p 490)endospore (p 491)nitrogen fixation
(p 493)obligate aerobe (p 491)obligate anaerobe
(p 491)toxin (p 492)
Archaebacteriaand Eubacteria
STUDY GUIDESTUDY GUIDE
CHAPTER 18 ASSESSMENT 499(t)Dr Kari LounatmaaScience Photo LibraryPhoto Researchers (bl)Fritz PolkingVisuals Unlimited (br)Michael AbbeyPhoto Researchers
To help you reviewviruses and bacteria use the Organiza-tional Study Fold on page 484
Section 182
cabdolglencoecomvocabulary_puzzlemaker
Color-enhanced TEM Magnification 76 000
LM Magnification 250
0484-0501 C18S2 BDOL-829900 8404 618 AM Page 499
500 CHAPTER 18 ASSESSMENT
Review the Chapter 18 vocabulary words listed inthe Study Guide on page 499 Match the wordswith the definitions below
1 a cell in which a virus replicates2 retrovirus uses this enzyme to make DNA
from its RNA3 viral DNA that is integrated into the host
cellrsquos chromosome4 method bacteria use to reproduce asexually5 tiny structure that contains bacterial DNA
encased by a tough outer covering
6 A ________ is never a part of a virusA nucleic acid C viral envelopeB protein coat D cell wall
7 Which of the following is NOT a commonbacterial shapeA B C D
8 What characteristic do viruses share with allliving organismsA respiration C replicationB metabolism D movement
9 During a lytic cycle after a virus enters thecell the virus ________A forms a provirusB replicatesC diesD becomes inactive
10 Prokaryotic cells have ________A organellesB a nucleusC mitochondriaD a cell wall
11 In ________ bacteria convert gaseous nitro-gen into ammonia nitrates and nitritesA nitrogen fixationB binary fissionC conjugationD attachment
12 Bacteria that require ________ for respira-tion are called ________A foodmdashobligate saprophytesB hydrogenmdasharchaebacteriaC oxygenmdashobligate anaerobesD oxygenmdashobligate aerobes
13 Some bacteria when faced with unfavorableenvironmental conditions produce struc-tures called ________A pili C toxinsB capsules D endospores
14 Which of the following would be most likelyto live in Utahrsquos Great Salt LakeA archaebacteriaB staphylococciC eubacteriaD viruses
15 Open Ended Scientists cannot grow about99 percent of all bacteria in the laboratoryHow might this inability interfere withunderstanding bacteria
16 Compare and Contrast What characteris-tics of life do viruses have Describe theways in which viruses differ from living cells
17 Open Ended Summarize the role ofmicroorganisms such as bacteria in main-taining and disrupting equilibrium includ-ing diseases in plants and animals
18 In addition toviruses prions such as bovine spongiformencephalopathy (mad cow disease) can causediseases Like viruses prions are nonlivingparticles What restrictions and regulationsdoes the United States government have inplace to prevent mad cow disease from com-ing to the US Research the answers andreport back to your class by making a posterdiscussing the prevention of this disease inthe US
REAL WORLD BIOCHALLENGE
cabdolglencoecomchapter_test
0484-0501 C18S2 BDOL-829900 8404 619 AM Page 500
CHAPTER 18 ASSESSMENT 501
Multiple ChoiceUse the diagram to answer questions 19 and 20
19 Which structure is the genetic material of the virusA AB BC CD D
20 Which structure is used for attachment to ahost bacteriumA A C CB B D D
21 Complete the concept map by using the fol-lowing vocabulary terms host cells viruseslysogenic cycle bacteriophages lytic cycle
One milliliter of E coli culture was added to eachof three petri dishes (I II and III) The dishes wereincubated for 36 hours and then the number ofbacterial colonies on each were counted
Study the table and the paragraph above andanswer questions 22ndash24
22 Which of the above dishes demonstrate thatcarbohydrates are necessary for the growthof E coliA dish I aloneB dishes I and IIC dishes II and IIID dish III
23 Which of the above dishes demonstrate thatvitamins enhance the growth of E coliA dishes I and IIB dishes II and IIIC dishes I and IIID none of the dishes
24 Which is an independent variable in thisexperimentA E coliB agarC carbohydratesD number of colonies
such as
1
2
to reproduce at once in a
to reproduce eventually in a
4 5
3
use
Growth of E coli Under Various Conditions
Petri Dish ColoniesNumber Medium Per Dish
I Agar and 35carbohydrates
II Agar carbohydrates 250and vitamins
III Agar and vitamins 0
A
B
C
D
cabdolglencoecomstandardized_test
Constructed ResponseGrid InRecord your answers on your answer document
25 Open Ended Describe the role of viruses in causing diseases and conditions such as acquiredimmune deficiency syndrome and smallpox
26 Open Ended Bacteria interact with humans in several ways Identify and describe the role of bacteria in both maintaining health such as digestion and causing disease in humans Cite specific examples
1c
1c
The assessed California standard appears next to the question
0484-0501 C18S2 BDOL-829900 8404 620 AM Page 501
- Biology The Dynamics of LifemdashCalifornia Edition
-
- Contents in Brief
-
- The California Biology Handbook
-
- California BiologyLife Sciences Content Standards
-
- California Content Standards to Biology The Dynamics of Life
- Biology The Dynamics of Life to California Content Standards
-
- How to Master the Content Standards
- Standards Practice Countdown
-
- Table of Contents
-
- Unit 1 What is biology
-
- Chapter 1 Biology The Study of Life
-
- Section 11 What is biology
-
- MiniLab 11 Predicting Whether Mildew Is Alive
- Careers in Biology Nature Preserve Interpreter
-
- Section 12 The Methods of Biology
-
- MiniLab 12 Testing for Alcohol
- Problem-Solving Lab 11
- Inside Story Scientific Methods
-
- Section 13 The Nature of Biology
-
- Problem-Solving Lab 12
- MiniLab 13 Hatching Dinosaurs
- Internet BioLab Collecting Biological Data
- Biology and Society Organic Food Is it healthier
-
- Chapter 1 Assessment
-
- BioDigest What is biology
- Unit 1 Standardized Test Practice
-
- Unit 2 Ecology
-
- Chapter 2 Principles of Ecology
-
- Section 21 Organisms and Their Environment
-
- MiniLab 21 Salt Tolerance of Seeds
- Problem-Solving Lab 21
- Careers in Biology Science Reporter
-
- Section 22 Nutrition and Energy Flow
-
- Problem-Solving Lab 22
- Physical Science Connection Conservation of Energy
- Physical Science Connection Conservation of Mass
- MiniLab 22 Detecting Carbon Dioxide
- Inside Story The Carbon Cycle
- Design Your Own BioLab How can one population affect another
- Biology and Society The EvergladesmdashRestoring an Ecosystem
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- Chapter 2 Assessment
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- Chapter 3 Communities and Biomes
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- Section 31 Communities
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- MiniLab 31 Looking at Lichens
- Problem-Solving Lab 31
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- Section 32 Biomes
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- Physical Science Connection Salinity and Density of a Solution
- Problem-Solving Lab 32
- MiniLab 32 Marine Plankton
- Inside Story A Tropical Rain Forest
- Investigate BioLab Succession in a Jar
- Connection to Literature Our National Parks by John Muir
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- Chapter 3 Assessment
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- Chapter 4 Population Biology
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- Section 41 Population Dynamics
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- MiniLab 41 Fruit Fly Population Growth
- Inside Story Population Growth
- Problem-Solving Lab 41
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- Section 42 Human Population
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- Problem-Solving Lab 42
- MiniLab 42 Doubling Time
- Investigate BioLab How can you determine the size of an animal population
- Connection to Chemistry Polymers for People
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- Chapter 4 Assessment
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- Chapter 5 Biological Diversity and Conservation
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- Section 51 Vanishing Species
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- MiniLab 51 Field Investigation
- Problem-Solving Lab 51
- Physical Science Connection Environmental Impact of Generating Electricity
- Physical Science Connection Wave Energy
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- Section 52 Conservation of Biodiversity
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- MiniLab 52 Conservation of Soil
- Problem-Solving Lab 52
- Internet BioLab Researching Information on Exotic Pets
- Connection to Art Photographing Life
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- Chapter 5 Assessment
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- BioDigest Ecology
- Unit 2 Standardized Test Practice
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- Unit 3 The Life of a Cell
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- Chapter 6 The Chemistry of Life
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- Section 61 Atoms and Their Interactions
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- Problem-Solving Lab 61
- Physical Science Connection Chemical Bonding and the Periodic Table
- Physical Science Connection Conservation of Mass in Chemical Reactions
- Careers in Biology WeedPest Control Technician
- MiniLab 61 Determine pH
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- Section 62 Water and Diffusion
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- Physical Science Connection The Structure of Water Molecules
- Physical Science Connection Density of Liquids
- Problem-Solving Lab 62
- MiniLab 62 Investigate the Rate of Diffusion
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- Section 63 Life Substances
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- Inside Story Action of Enzymes
- Design Your Own BioLab Does temperature affect an enzyme reaction
- BioTechnology The Good News and the Bad News About Cholesterol
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- Chapter 6 Assessment
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- Chapter 7 A View of the Cell
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- Section 71 The Discovery of Cells
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- Physical Science Connection Lenses and the Refraction of Light
- MiniLab 71 Measuring Objects Under a Microscope
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- Section 72 The Plasma Membrane
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- Problem-Solving Lab 71
- Physical Science Connection Solubility and the Nature of Solute and Solvent
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- Section 73 Eukaryotic Cell Structure
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- Problem-Solving Lab 72
- MiniLab 72 Cell Organelles
- Physical Science Connection Conservation of Energy
- Inside Story Comparing Animal and Plant Cells
- Investigate BioLab Observing and Comparing Different Cell Types
- Connection to Literature The Lives of a Cell by Lewis Thomas
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- Chapter 7 Assessment
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- Chapter 8 Cellular Transport and the Cell Cycle
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- Section 81 Cellular Transport
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- MiniLab 81 Cell Membrane Simulation
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- Section 82 Cell Growth and Reproduction
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- Problem-Solving Lab 81
- Problem-Solving Lab 82
- Inside Story Chromosome Structure
- MiniLab 82 Seeing Asters
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- Section 83 Control of the Cell Cycle
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- Problem-Solving Lab 83
- Investigate BioLab Where is mitosis most common
- Connection to Health Skin Cancer
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- Chapter 8 Assessment
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- Chapter 9 Energy in a Cell
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- Section 91 The Need for Energy
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- Problem-Solving Lab 91
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- Section 92 Photosynthesis Trapping the Suns Energy
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- MiniLab 91 Separating Pigments
- MiniLab 92 Use Isotopes to Understand Photosynthesis
- Inside Story The Calvin Cycle
- Biotechnology Careers Biochemist
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- Section 93 Getting Energy to Make ATP
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- Inside Story The Citric Acid Cycle
- Problem-Solving Lab 92
- MiniLab 93 Determine if Apple Juice Ferments
- Internet BioLab What factors influence photosynthesis
- Connection to Chemistry Plant Pigments
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- Chapter 9 Assessment
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- BioDigest The Life of a Cell
- Unit 3 Standardized Test Practice
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- Unit 4 Genetics
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- Chapter 10 Mendel and Meiosis
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- Section 101 Mendels Laws of Heredity
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- MiniLab 101 Looking at Pollen
- Problem-Solving Lab 101
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- Section 102 Meiosis
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- Problem-Solving Lab 102
- MiniLab 102 Modeling Crossing Over
- Inside Story Chromosome Mapping
- Internet BioLab How can phenotypes and genotypes of plants be determined
- Connection to Math A Solution from Ratios
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- Chapter 10 Assessment
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- Chapter 11 DNA and Genes
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- Section 111 DNA The Molecule of Heredity
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- Problem-Solving Lab 111
- Inside Story Copying DNA
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- Section 112 From DNA to Protein
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- Problem-Solving Lab 112
- MiniLab 111 Transcribe and Translate
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- Section 113 Genetic Changes
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- Physical Science Connection Gamma Radiation as a Wave
- Careers in Biology Genetic Counselor
- Problem-Solving Lab 113
- MiniLab 112 Gene Mutations and Proteins
- Investigate BioLab RNA Transcription
- BioTechnology Scanning Probe Microscopes
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- Chapter 11 Assessment
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- Chapter 12 Patterns of Heredity and Human Genetics
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- Section 121 Mendelian Inheritance of Human Traits
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- MiniLab 121 Illustrating a Pedigree
- Problem-Solving Lab 121
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- Section 122 When Heredity Follows Different Rules
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- Problem-Solving Lab 122
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- Section 123 Complex Inheritance of Human Traits
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- Inside Story The ABO Blood Group
- Problem-Solving Lab 123
- MiniLab 122 Detecting Colors and Patterns in Eyes
- Design Your Own BioLab What is the pattern of cytoplasmic inheritance
- Connection to Social Studies Queen Victoria and Royal Hemophilia
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- Chapter 12 Assessment
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- Chapter 13 Genetic Technology
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- Section 131 Applied Genetics
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- Problem-Solving Lab 131
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- Section 132 Recombinant DNA Technology
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- MiniLab 131 Matching Restriction Enzymes to Cleavage Sites
- Inside Story Gel Electrophoresis
- Problem-Solving Lab 132
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- Section 133 The Human Genome
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- MiniLab 132 Storing the Human Genome
- Biotechnology Careers Forensic Analyst
- Problem-Solving Lab 133
- Investigate BioLab Modeling Recombinant DNA
- BioTechnology New Vaccines
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- Chapter 13 Assessment
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