LS 204 Microbiology Chapter 7

Student Learning Outcomes:

• 1. Name some organisms that are microorganisms

• 2. Explain the importance of microorganisms to our everyday lives

• 3. Describe the importance of and differences between viruses, viroids, and prions

• 4. Discuss why it is important to understand the growth requirements, metabolism, and genetics of bacteria

• 5. Explain how microbes cause disease and how we control them, both inside and outside of the body

Questions starting:

• What sorts of organisms would be called microorganisms – give examples

• What are some ways we benefit from microbes?

• What is a virus?

• How do bacteria divide?

• What are some ways the human body defends itself against disease?

Examples of microorganisms of 3 Domains (Fig. 7.1):

• Bacteria Archaea Eukarya

Example microorganisms of the three Domains

• Domain Archaea = prokaryotes; ‘extremophiles’; Halobacterium; Pyrococcus No human pathogens; many unusual metabolic patterns

• Domain Bacteria = prokaryotes; Escherichia coli, Staphylococcus aureus; Bacillus anthracisBeneficial organisms and human pathogens;

also unusual metabolic patterns

• Domain Eukarya: • Kingdom Protista – pathogens like Amoeba, Trypanosoma, • Kingdom Fungi – pathogens include yeast like Candida• Kingdom Animalia – worms include Schistosoma• Kingdom Plantae – algae like Chlamydomonas

Importance of microorganisms• Pathogens cause disease in humans, other organisms

• Beneficial organisms: • cyanobacteria and algae in oceans do photosynthesis

and produce sugar and oxygen• fungi and Bacteria recycle waste products, organic

molecules, oil spill• fungi and Bacteria produce food and drinks (yoghurt,

beer, wine)• normal microbiota = microbes on our skin, digestive

system that protect from pathogens

Naming microbes• Bacteria = Domain Bacteria;• bacteria = prokaryotes, includes Domain Archaea• 1 bacterium, 2 bacteria

• Binomial nomenclature: Species genus • ex. Escherichia coli• Spell out genus first time it’s used, • Afterwards, can abbreviate: E. coli• Write names in italics

Hierarchy in Domain Bacteria

• The groupings help understand shared characteristics, antibiotics that will kill them

• Ex. E. coli is Domain Bacteria, Phylum Proteobacteria; Family Enterobacteriaceae

• Family includes other intestinal inhabitants and pathogen genera such as Salmonella, Enterobacter, Shigella)

Names can reflect shapes, sizes, arrangement of cells

• Coccus (cocci plural) = round • Bacillus (bacilli) = rod• Spirilla = spiral-shaped

• Strepto = chains• Staphylo = clusters• • Diplo- = two

Names can indicate properties

• Escherichia coli Eponym for Dr. Escher; coli for colon

• Micrococcus roseus small red circles

• Mycobacterium tuberculosiswaxy cell walls, causes tuberculosis (tubercles in lungs)

• Streptococcus pneumoniaround cells in chains, causes pneumonia

• Bacillus megaterium very large rod-shaped organism

• Thiobacillus rod-shaped organism that eats sulfur

More microbes: Viruses, Viroids, Prions

• Not considered ‘living’ since not cells, lack ability to reproduce on own (use host resources).

• Virus (Fig. 7.4) has nucleic acid (DNA OR RNA) wrapped in protein coat

• Some also have envelope (made of host’s membrane with viral proteins)

• [Bacteriophages infect bacteria]• Animal viruses infect animals

HPV

Virus examples

herpesvirus

Shapes of virus capsids

Virus quantification

Plaque assay – grow viruses on lawn of susceptible host cells; Infection of host cell, replication and infection of adjacent cells -> hole or plaque

Virus life cycle (Fig. 7.4):

• Attachment: specific molecules on virus and receptors on host

• Penetration: all or some of virus enters• Uncoating: protein coat removed• Biosynthesis: of viral nucleic acids and proteins• mRNA -> proteins using host ribosomes; • DNA or RNA of genome is reproduced• Release: virus breaks out of cell or buds

through membrane

Virus life cycle (Fig. 7.4)

HerpesvirusA DNA virus

Retrovirus life cycle (Fig. 7.4)

HIV (Human immunodeficiency virus)A retrovirus: RNA genome, converts to DNA

• Viroid : nucleic acid only – some plant diseases

• Prions – only protein – animal diseases:• Spongiform encephalopathy (Mad Cow disease, elk wasting

disease) Creutzfeld-Jacob disease (CJD)

Examples of microorganisms of 3 Domains (Fig. 7.1):

• Bacteria Archaea Eukarya

How bacteria work tiny factories of only 1 cell compartment

• Growth and nutrition:• Divide by binary fission (Fig. 7.5) – 1 cell ->2 cells -> 4 cells

• Many different metabolic, nutrition patterns –

more diverse than eukaryotes• Latin terms refer to metabolic patterns:

How bacteria work tiny factories of only 1 cell compartment

• Producers include Photoautotrophs (photosynthesis, use CO2 + H2O to make sugars + O2)

• Human pathogens are mostly Mesophiles (grow at middle temperatures) • Some bacteria are thermophiles (high temperatures)• Some bacteria are psychrophiles (low temperatures)

cyanobacteria

Oxygen requirements:• obligate aerobes (skin, lungs)

– Pseudomonas aeruginosa • facultative anaerobes (gut)

– Escherichia coli• obligate anaerobes (puncture wound)

– Clostridium tetani

• Metabolism: similar to eukaryotes, especially for pathogens, but only 1 compartment

• Catabolism to take apart molecules and gain ATP, building blocks;

• Anabolism uses ATP and small molecules to build macromolecules

Typical metabolism:Glycolysis: 6C sugar (glucose) -> to 3-C pyruvate + ATP +

NADH (e- carriers)• occurs in cytoplasm of bacteria and eukaryotes

Krebs cycle (citric acid cycle): 3-C pyruvate -> CO2 + ATP + NADH + FADH2

Electron transport chain (aerobic respiration):• NADH + FADH2 + O2 -> lots of ATP + H2O + NAD + FAD • Occurs in cytoplasm of bacteria; mitochondria of eukaryotes

Metabolism cont.Fermentation: alternative path that does not

require oxygen: occurs in cytoplasm• Pyruvate -> an organic molecule; a low energy

path that recycles the NADH

• Yeast make alcohol + CO2; (muscle cells lactic acid)• Bacteria make lactic acid, butyric acid, other products• (Fig. 7.6 concept map of relationships of pathways)

Microbial GeneticsDNA -> RNA -> protein

(Fig. 7.7)

• Transcription is DNA copied into rRNA, tRNA or mRNA

• Translation is synthesis of protein from mRNA on the ribosome

Examples of microorganisms of 3 Domains (Fig. 7.1):

• Bacteria Archaea Eukarya

Bacterial gene transfer

Bacteria can transfer some genes from one to another (even between species) (Fig. 7.8):

• Transformation = piece of DNA can go into another cell • Transduction = piece of bacterial DNA packaged in

bacteriophage coat goes into other cell• Conjugation = two bacteria attach and one donates copy

of some genes

*** Antibiotic-resistant bacteria can transfer these genes to other bacteria

Bacterial gene transfer

methods

Microbial control – how we control them.

• Physical and chemical agents:• Disinfectants• Sterilants (gas, autoclave) • Sanitizers • Radiation

• Chemotherapeutics (antibiotics) – compounds taken inside us to kill them

Principles of disease• Each pathogen has its niche – temperature, humidity,

cell type, oxygen

• Epidemiology – study of epidemics, or sudden large numbers of cases of disease in population.

• Epidemiologists look for patterns of disease, moniter numbers

• Note Latin terms, name of disease for body part: • meningitis = inflammation of meninges• bacteremia = bacteria in the blood system

Defenders against disease (Table 7.9)

• Innate immunity (nonspecific)• First line = intact skin, mucus membranes, normal microbiota

• Second line = natural killer cells phagocytic white blood cells, inflammation, fever

Adaptive (specific) immunity

• Specialized lymphocytes: T cells and B cells• Antibodies produced by B cells circulate in blood stream• Antibodies recognize specific antigens (structures) on the pathogen• Vaccines stimulate production of ‘memory’ T cells and B cells to defend future infection