Chapter 11

The Prokaryotes: Domains of Bacteria

and Archaea

© 2013 Pearson Education, Inc.

Presented by

D. Mona Othman AlbureikanLectures

(11, 12, 13,14,15)

The Prokaryotes Groups

Domain Bacteria

• Proteobacteria

– Gram-negative

– Chemoheterotrophic

– It separated into five classes: alphaproteobacteria, beta proteobacteria, gammaproteobacteria, delta proteo bacteria, and epsilonproteobacteria.

The Alphaproteobacteria

• Pelagibacter ubique

• it is play an important role in the Earth's carbon cycle.

• 20% of prokaryotes in oceans.

• 1354 genes

• Human pathogens

– Bartonella

• B. henselae: cat-scratch disease

– Brucella: brucellosis

– Ehrlichia: ehrlichiosis (a sometimes fatal disease)

– Rickettsia: arthropod-borne, spotted feversR. prowazekii: epidemic typhus (transmitted by lice)R. typhi: endemic murine typhus (transmitted by rat fleas)R. rickettsii: Rocky Mountain spotted fever (transmitted by ticks)

• Obligate intracellular parasites

– Ehrlichia: ehrlichiosis (a sometimes fatal disease)

– Rickettsia: ,R. prowazekii: ,R. typhi: , R. rickettsii:

The Alphaproteobacteria

• Wolbachia: live in insects and other animals.

• The most common infectious bacterial genus in the world.

Wolbachia are red inside the cells of this fruit fly embryo.

• Have prosthecae

– Caulobacter: stalked bacteria found in lakes

– Hyphomicrobium: budding bacteria found in lakes

Caulobacter.

Hyphomicrobium, a type of budding bacterium.

Hypha

BudBud

Holes infilter

The Alphaproteobacteria

• Plant pathogen

– Agrobacterium: insert a plasmid into plant cells, inducing a tumor.

The Alphaproteobacteria

Crown gall disease on a rose plant.

Crown gall

Oxidize nitrogen for energy

– Fix CO2

• Nitrobacter: NH3 NO2–

• Nitrosomonas: NO2– NO3

–

The Alphaproteobacteria

• Nitrogen-fixing bacteria

– Azospirillum

• Grow in soil, using nutrients excreted by plants

• Fix nitrogen

– Rhizobium

• Fix nitrogen in the roots of plants

• Produce acetic acid from ethanol

– Acetobacter

– Gluconobacter

The Alphaproteobacteria

• Thiobacillus– Oxidize sulfur: H2S SO4

2– (important in the sulfur cycle)

• Sphaerotilus

– Form sheaths

The Betaproteobacteria

Sphaerotilus natans.

Bacterial cell

Sheath

The Betaproteobacteria

• Bordetella

– B. pertussis

– Rods, cause of pertussis, or whooping cough.

• Burkholderia

– Nosocomial infections

- Zoogloea , is important in the

sewage-treatment processes, such

as the activated sludge system .

- Neisseria , pathogenic species

include bacterium Neisseria

gonorrhoea and N. meningitidis the

agent of meningococcal meningitis.

The gram-negative coccus Neisseriagonorrhoeae.

Capsule

Fimbriae

• Pseudomonadales

– Pseudomonas

• Opportunistic pathogens, it can infect the urinary tract, burns, and wounds, and can cause blood infections (sepsis).

The Gammaproteobacteria

Pseudomonas

• Pseudomonadales

– Moraxella

• Conjunctivitis

– Azotobacter and Azomonas

• Nitrogen- fixation

• Legionellales

– Legionella

• Found in streams, warm-water pipes, cooling towers

• L. pneumophilia

– Coxiella

• Q fever transmitted via aerosols or milk

The Gammaproteobacteria

• Vibrionales

– Found in coastal water

• Vibrio cholerae causes cholera

• V. parahaemolyticuscauses gastroenteritis.

Coxiella burnetii, the cause of Q fever.

Vibrio cholerae.

• Enterobacteriales (called enterics)

• Peritrichous flagella; facultatively anaerobic, produce proteins called bacteriocins that cause the lysis of closely related species of bacteria.

• Enterobacter , can cause urinary tract infections and hosp ital-acquired infections.

• Erwinia, species are plant pathogens

• Escherichia, is not usually pathogenic

• Klebsiella, Many isolates arc capable of fixing nitrogen from the atmosphere, Klebsiella pneumoniae causes pneumonia in humans.

• Proteus, many infections of the urinary tract and in wou nds.

• Salmonella, Almost all members of the genus Salmonella are potentially pathogenic.

• Serratia, cause of many urinary and respiratory tract infections in hospitals.

• Shigella, responsible for a disease called bacillary dysentery, or shigellosis.

• Yersinia, causes plague, the Black Death of medieval Europe.

The Gammaproteobacteria

• Pasteurellales

– Pasteurella

• Cause pneumonia and septicemia

– Haemophilus

• Require X (heme) and V (NAD+, NADP+) factors

The Gammaproteobacteria

• Beggiatoa

– Oxidize H2S to S0 for energy

• Francisella

– causes the disease tularemia.

• Desulfovibrionales

– Use S instead of O2 as final electron acceptor

The Deltaproteobacteria

Bdellovibrio bacteriovorus.

Myxococcales. (Myxoeoceus)

MyxosporesMyxospores are resistant resting cells released from sporangioles upon favorable conditions.

GerminationMyxospores germinate and form gram-negative vegetative cells, which divide to reproduce.

Vegetative growth cycleVegetative myxobacteria are motile by gliding, forming visible slime trails.

AggregationUnder favorable conditions, the vegetative cells swarm to central locations, forming an aggregation.

Mounding Aggregations of cells heap up into a mound, an early fruiting body.

Mounds of myxobacteria differentiate into a mature fruiting body, which produces myxospores packed within sporangioles.

Sporangiole

Myxobacteria fruiting body

Myxospores

• Campylobacter

– Gastroenteritis

• Helicobacter

– Peptic ulcers

– Stomach cancer

The Epsilonproteobacteria

Heliobacter pylori.

The Gram-Positive Bacteria

- The gram-positive bacteria can be divided into two groups.- Those that have a high G + C ratio, and those that have a low G + C Ratio.

Firmicutes (Low G + C)

Firmicutes (Low G + C)

• Clostridium

– Endospore-producing

– Botulism, caused and gas gangrene.

• Epulopiscium

Endospore

(Clostridiales)

Clostridium difficile. Epulopiscium fishelsoni.

• Bacillus

– Endospore-producing rods

– Only a few are pathogenic to humans.

– Bacillus anthracis causes anthrax.

– Several species produce antibiotics.

• Staphylococcus

– Cocci.

– It produces an enterotoxin that causes vomiting and nausea when ingested; it is one of the most common causes of food poisoning.

Firmicutes (Low G + C)

(Bacillales)

• Lactobacillus (used commerciall y in the production of sauerkraut, pickles, buttermilk, and yogurt)

– Streptococcus (responsible for more illnesses)

• Enterococcus (responsible for much of the infections of surgical wounds and the urinary tract)

– Listeria (serious damage to the fetus)

Firmicutes (Low G + C)

(Lactobacillales)

(Mycoplasmatales)

- Pleomorphic because they lack a cell wall - M. pneumoniae cause of pneumonia.

Actinobacteria (High G + C)

The Gram-Positive Bacteria

• Actinomyces

• Corynebacterium

• Frankia

• Gardnerella

• Mycobacterium

• Nocardia

• Propionibacterium

• Streptomyces

Actinobacteria (High G + C)

Filaments

Conidiosporesin coils

Streptomyces.

Drawing of a typical streptomycete showing filamentous, branching growth with asexual reproductive conidiospores at the filament tips.

Actinomyces.

Actinobacteria (High G + C)

• Oxygenic photosynthesis

• Anoxygenic photosynthesis

Phototrophic

2H2O + CO2

light(CH2O) + H2O + O2

2H2S + CO2

light(CH2O) + H2O + 2S0

Nonproteobacteria Gram-Negative Bacteria

Oxygenic Photosynthetic Bacteria

• Cyanobacteria

– Gliding motility, Fix nitrogen

Phototrophic

Nonproteobacteria Gram-Negative Bacteria

Heterocysts

(b) A unicellular, nonfilamentous cyanobacterium, Gloeocapsa. Groups of these cells, which divide

by binary fission, are held together by the surrounding glycocalyx.

(a) Filamentous cyanobacterium showing heterocysts, in which nitrogen-fixing

activity is located. Cyanobacteria

• The planctomycetes, a group of gram-negative, budding bacteria.• Gemmata obscuriglobus

– Double internal membrane around DNA

Nonproteobacteria Gram-Negative Bacteria

Planctomycetes

Nucleoid

Nuclear envelope

Gemmata obscuriglobus.

• Chlamydia trachomatis ( Trachoma)

• Chlamydophila pneumoniae

Nonproteobacteria Gram-Negative Bacteria

Chlamydias

– Anaerobic

• Bacteroides are found in the mouth and large intestine

• Cytophaga: degrade cellulose in soil

Nonproteobacteria Gram-Negative Bacteria

Bacteroidetes

Fusobacterium

Are found in the mouthMay be involved in dental diseases

Spirochaetes

- Treponema pallidlum cause of syphilis

- Borrelia Members of the genus Borrelia cause serious diseases that are

usually transmitted by ticks or lice,

- Leptospira Leptospirosis is a disease usually spread to humans by water

contaminated by Leptospira .

This cross section of a spirochete shows numerous axial filaments between the dark cell and the outer sheath.

This micrograph of a portion of Treponemapallidum shows the sheath, which has shrunk away from the cell, and two axial filaments attached near one of the cell under the sheath.

Axial filaments

Sheath

Axial filaments

Sheath

Spirochetes.

Nonproteobacteria Gram-Negative Bacteria

• Purple sulfur

• Purple nonsulfur

• Green sulfur

• Green nonsulfur

Anoxygenic Photosynthetic Bacteria

Purple sulfur bacteria.

Domain Archaea

Extremophiles

• Hyperthermophiles

– Pyrodictium

– Sulfolobus

• Methanogens

– Methanobacterium

• Extreme halophiles

– Halobacterium

Figure 11.27 Archaea.

Microbial Diversity

• bacteria as small as 0.02 to 0.03 µm (nanobacteria)

• Few of the total number of different prokaryotes have been isolated and identified .

• PCR can be used to uncover the presence of bacteria that can't be cultured in the laboratory.

• The polymerase chain reaction (PCR)

• PCR indicates up to 10,000 bacteria per gram of soil

• Many bacteria have not been identified because they– Have not been cultured

– Need special nutrients

– Are a part of complex food chains requiring the products of other bacteria

– Need to be cultured to understand their metabolism and ecological role

Microbial Diversity

References

• Microbiology: An Introduction Plus MasteringMicrobiology with eText - Access Card Package (11th Edition) Hardcover – January 2, 2012 by Gerard J. Tortora, Berdell R. Funke, Christine L. Case.

• Some pictures from different sits.