chapter 11 the prokaryotes: domains bacteria and archaea part 1

Chapter 11

The Prokaryotes: Domains Bacteria and Archaea

Part 1

The Prokaryotes: Domains Bacteria and Archaea

• One circular chromosome (no histones), not in a membrane (no nucleus)

• No organelles

• 70S ribosomes

• Peptidoglycan cell walls (mainly bacteria)

• Binary fission

Domain Archaea

• Discovered in late 1970s; highly diverse group

• rRNA sequence differ from Domains Bacteria & Eukarya

• Cell wall lacks peptidoglycan; a few lack cell wall

• Some are gram-positive and some are gram-negative

• Binary fission, fragmentation or budding

• Most are morphologically similar to bacteria (rods, cocci, and helixes); but some are very unusual

Domain Archaea

Figure 11.25

Disk-shaped Pyrodictium abyssi

Domain Archaea

• Physiologically diverse (aerobic, facultative anaerobe, and strict/obligate anaerobe)

• Chemoautotrophs, photoautotrophs, and chemoheterotrophs

• Frequent inhabitants of extreme environments (heat, cold, acidity, and pressure)

Domain Archaea

• Hyperthermophiles– Pyrodictium– Sulfolobus

• Methanogens (economic importance)– Methanobacterium derive energy from

combining hydrogen with carbon dioxide to form methane

• Extreme halophiles – Halobacterium– Halococcus

Domain Bacteria• Proteobacteria

– Mythical Greek god, Proteus, who could assume many shapes

– Gram-negative; many are chemoheterotrophic bacteria

– presumed to have arisen from a common photosynthetic ancestor; few are photosynthetic today

• The alpha () proteobacteria– As a group, most are capable of growth at very

low levels of nutrients

The (alpha) Proteobacteria

• Chemoautotrophs and chemo- heterotrophs

• Include agriculturally important bacteria, and several plant and human pathogens

• Some have unusual morphology

• prosthecae: protrusions such as stalks or buds– Caulobacter. Stalked

bacteria found in lakes– Hyphomicrobium.

Budding bacteria found in lakes

The (alpha) Proteobacteria

Figure 11.2 & 3

• Human pathogens:– Bartonella: several members are human

pathogens• B. hensela Cat-scratch disease

– Brucella: small nonmotile coccobacilli; obligate parasites of mammals and cause diseases brucellosis

The (alpha) Proteobacteria

• Obligate intracellular parasites: reproduce only within a mammalian cell– Ehrlichia: tick-borne, cause ehrlichiosis – Rickettsia: arthropod-borne (e.g. lice, rat fleas, and

ticks), cause spotted fevers• R. prowazekii Epidemic typhus

• R. typhi Endemic murine typhus

• R. rickettsii Rocky Mountain Spotted Fever

The (alpha) Proteobacteria

The (alpha) Proteobacteria

Figure 11.1

• Wolbachia. Live in insects and other animals– infect over a million

species of insects as well as spiders, millipedes, mites, crustaceans, and nematodes.

The (alpha) Proteobacteria

• Plant pathogen:– Agrobacterium

tumefaciens• causes a

disease called crown gall by inserting a (Ti) plasmid into plant cells, & inducing a tumor

The (alpha) Proteobacteria

Figure 9.17

• Agriculturally important genera (Nitrogen-fixing & nitrifying bacteria)– Azospirillum

• Grow in soil, using nutrients excreted by plants

• Fix nitrogen

– Rhizobium• Fix nitrogen in the

roots of plants

The (alpha) Proteobacteria

Figure 27.5

– Nitrobacter oxidize nitrogen (ammonium to nitrite) for energy

– Nitrosomonas oxidize nitrogen (nitrite to nitrate) for energy

– Both are chemoautotrophic (fix CO2 as C source) . • Important for the environment and to agriculture

• Industrially important genera– Acetobacter Both produce acetic acid– Gluconobacter from ethyl alcohol

The (alpha) Proteobacteria

The (beta) Proteobacteria

• Considerable overlap between the - and -proteobacteria, esp. among the nitrifying bacteria

• Many use nutrient substances that diffuse away form areas of anaerobic decomposition of organic matter

• Chemoautotrophs & chemoheterotrophs• Include several important pathogenic

bacteria

The (beta) Proteobacteria

• Human pathogens– Neisseria :

chemoheterotrophic, cocci

• N. meningitidis

• N. gonorrhoeae

– Bordetella: chemo-heterotrophic, rods

• B. pertussis

– Burkholderia: cause nosocomial infections

The (beta) Proteobacteria

Figure 11. 6

The (beta) Proteobacteria

• Sphaerotilus– Chemoheterotophic– form sheaths – Cause problem in

sewage treatment

• Spirillum– Chemoheterotrophic– Helical shaped, but

use flagella (no axial filaments)

Figures 11.4 & 11.5

• Environmentally important genera– Thiobacillus: Chemoautotrophic, important in

sulfur cycle by oxidizing sulfur (H2S SO42–)

• Industrially important genera– Zoogloea: Slimy masses in aerobic sewage-

treatment processes

The (beta) Proteobacteria

The (gamma) Proteobacteria

• Largest subgroup of the proteobacteria; include a great variety of physiological types

• Many are human and plant pathogens

The (gamma) Proteobacteria

• Pseudomonadales:– Pseudomonas

• Opportunistic pathogens

• Metabolically diverse

• Polar flagella

– Azotobacter and Azomonas: Nitrogen fixing– Moraxella: Conjunctivitis

The (gamma) Proteobacteria

Figure 11.7

• Legionellales:– Legionella

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

• L. pneumophilia

– Coxiella• Q fever transmitted

via aerosols or milk

The (gamma) Proteobacteria

Figure 24.15b

• Vibrionales:– Found in coastal water

• Vibrio cholerae causes cholera

• V. parahaemolyticus causes gastroenteritis

The (gamma) Proteobacteria

Figure 11.8

• The (gamma) Proteobacteria– Enterobacteriales (enterics):

• Peritrichous flagella, facultatively anaerobic– Enterobacter– Erwinia– Escherichia– Klebsiella– Proteus– Salmonella– Serratia– Shigella– Yersinia

The (gamma) Proteobacteria

The (gamma) Proteobacteria

Figure 11.9a, b

• Pasteurellales:– Pasteurella

• Cause pneumonia and septicemia

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

The (gamma) Proteobacteria

• Beggiatoa– Chemoautotrophic, oxidize H2S to S0 for

energy

• Francisella– Chemoheterotrophic, tularemia

The (gamma) Proteobacteria

• Actinomyces

• Corynebacterium

• Frankia

• Gardnerella

• Mycobacterium

• Nocardia

• Propionibacterium

• Streptomyces

Actinobacteria

Figure 11.20b

• Actinomyces

• Corynebacterium

• Frankia

• Gardnerella

• Mycobacterium

• Nocardia

• Propionibacterium

• Streptomyces

Actinobacteria

Figure 11.20b

The (delta) Proteobacteria

• Include some bacteria that are predators on other bacteria.

• Contributors to the sulfur cycle

– Bdellovibrio: prey on other gram-negative bacteria

– Desulfovibrionales: sulfur reducing bacteria; use S instead of O2 as final electron acceptor

• Release millions of tons of H2S into the atmosphere every year and plays a key part in the sulfur cycle

– Myxococcales: gliding; cells aggregate to form myxospores; also predatory on other bacteria

The (delta) Proteobacteria

The (delta) Proteobacteria

Figure 11.10a

The (delta) Proteobacteria

Figure 11.1b

The (epsilon) Proteobacteria

• Slender gram-negative rods; helical or vibroids

• Vibroid: helical bacteria that do not have a complete turn

• Human pathogens– Campylobacter: one polar flagellum;

microaerophilic vibrios; cause gastroenteritis• C. fetus

• C. jejuni

The (epsilon) Proteobacteria

Figure 11.1a

– Helicobacter: multiple flagella; microaerophilic curbed rods

• H. pylori causes peptic ulcers & Stomach cancer

The (epsilon) Proteobacteria

Figure 11.11