Transcript Chapter 11
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 gramnegative Domain Archaea • Binary fission, fragmentation or budding • Most are morphologically similar to bacteria (rods, cocci, and helixes); but some are very unusual Disk-shaped Pyrodictium abyssi Figure 11.25 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 chemoheterotrophs • Include agriculturally important bacteria, and several plant and human pathogens The (alpha) Proteobacteria • Some have unusual morphology • prosthecae: protrusions such as stalks or buds – Caulobacter. Stalked bacteria found in lakes – Hyphomicrobium. Budding bacteria found in lakes Figure 11.2 & 3 The (alpha) Proteobacteria • 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 • R. typhi • R. rickettsii Epidemic typhus Endemic murine typhus Rocky Mountain Spotted Fever The (alpha) Proteobacteria Figure 11.1 The (alpha) Proteobacteria • 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 Figure 9.17 The (alpha) Proteobacteria • 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 Figure 27.5 The (alpha) Proteobacteria – 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 – Gluconobacter Both produce acetic acid from ethyl alcohol 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 The (beta) Proteobacteria • Human pathogens – Neisseria : chemoheterotrophic, cocci • N. meningitidis • N. gonorrhoeae – Bordetella: chemoheterotrophic, rods • B. pertussis – Burkholderia: cause nosocomial infections 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 The (beta) Proteobacteria • Environmentally important genera – Thiobacillus: Chemoautotrophic, important in sulfur cycle by oxidizing sulfur (H2S SO42–) • Industrially important genera – Zoogloea: Slimy masses in aerobic sewagetreatment processes The (gamma) Proteobacteria • Largest subgroup of the proteobacteria; include a great variety of physiological types • Many are human and plant pathogens The (gamma) Proteobacteria The (gamma) Proteobacteria • Pseudomonadales: – Pseudomonas • Opportunistic pathogens • Metabolically diverse • Polar flagella – Azotobacter and Azomonas: Nitrogen fixing – Moraxella: Conjunctivitis Figure 11.7 The (gamma) Proteobacteria • Legionellales: – Legionella • Found in streams, warm-water pipes, cooling towers • L. pneumophilia – Coxiella • Q fever transmitted via aerosols or milk Figure 24.15b The (gamma) Proteobacteria • Vibrionales: – Found in coastal water • Vibrio cholerae causes cholera • V. parahaemolyticus causes gastroenteritis Figure 11.8 The (gamma) Proteobacteria • The (gamma) Proteobacteria – Enterobacteriales (enterics): • Peritrichous flagella, facultatively anaerobic – – – – – – – – – Enterobacter Erwinia Escherichia Klebsiella Proteus Salmonella Serratia Shigella Yersinia The (gamma) Proteobacteria Figure 11.9a, b The (gamma) Proteobacteria • 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 Actinobacteria • • • • • • • Actinomyces Corynebacterium Frankia Gardnerella Mycobacterium Nocardia Propionibacteriu m • Streptomyces Figure 11.20b Actinobacteria • • • • • • • Actinomyces Corynebacterium Frankia Gardnerella Mycobacterium Nocardia Propionibacteriu m • Streptomyces Figure 11.20b The (delta) Proteobacteria • Include some bacteria that are predators on other bacteria. • Contributors to the sulfur cycle The (delta) Proteobacteria – 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 Figure 11.10a The (delta) Proteobacteria Figure 11.1b The (epsilon) Proteobacteria • Slender gram-negative rods; helical or vibroids The (epsilon) Proteobacteria • Vibroid: helical bacteria that do not have a complete turn • Human pathogens – Campylobacter: one polar flagellum; microaerophilic vibrios; cause gastroenteritis • C. fetus • C. jejuni Figure 11.1a The (epsilon) Proteobacteria – Helicobacter: multiple flagella; microaerophilic curbed rods • H. pylori causes peptic ulcers & Stomach cancer Figure 11.11