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Transcript
LECTURE 12 Let’s look at some of the basal branches of the Bacterial tree…. THE BACTERIA Aquifex and Thermotoga Thermotoga has a sheath, like a toga • oldest branches of the Bacteria • hyperthermophiles • Aquifex spp. are H2 oxidizers and fix CO2 by running the TCA cycle backwards. One of the only hyperthermophic aerobes Use of H2 by so many beeply branching thermophiles suggests H2 was very common on the early earth Thermotoga lives near submarine hydrothermal vents, have a protein sheath (“toga”). Anaerobic fermentors….. Deinococcus - Thermus Deinococcus-Thermus • 2 main groups: > Deinococci > Thermales • Deinococcus can survive extremely high levels of UV and Gamma radiation. Is Gm- but outer membrane is surrounded by a protein sheath (S-layer) thus it stains Gm+. Has several copies of chromosome per cell and is very efficient at DNA repair….. The Proteobacteria • largest cultured group of bacteria - 380 genera & at least 1500 species! • 5 major groups (“classes”): !Alphaproteobacteria !Betaproteobacteria !Gammaproteobacteria !Deltaproteobacteria !Epsilonproteobacteria ALPHAPROTEOBACTERIA (cont.) ALPHAPROTEOBACTERIA Rickettsia • many important pathogens e.g. cause Rocky Mountain spotted fever, Typhus….. • genome sequencing shows that they are very similar to mitochondria - probably ancestor of Rickettsia was involved in endosymbiotic event. ALPHAPROTEOBACTERIA (cont.) Caulobacteraceae & Hyphomicrobiaceae These 2 groups of bacteria have some sort of appendage: > A prostheca - an extension of the cell that is narrower than the mature cell • Some Hyphomicrobium species are methylotrophs - can use methane or other 1-carbon compounds as energy and carbon sources > Reproduction by budding (see lec. 5) - reproduction via a small protrusion that enlarges to form a new cell. Fig. 11.24. Budding in Hyphomicrobium Fig. 11.23. Caulobacter life cycle ALPHAPROTEOBACTERIA (cont.) Rhizobium - symbionts within root nodules of plants and fix nitrogen Fig. 11.20. A crown gall - plant tumor induced chemically by Agrobacterium Agrobacterium - does not stimulate root nodule formation or fix nitrogen. Instead, these bacteria invade plant tissues and cause tumors - crown gall disease. ALPHAPROTEOBACTERIA (cont.) Rhizobium is the most intensively studied symbiotic (mutualistic) bacterium. Very important agriculturally (think soy beans, beans, clover & other legumes etc.) Plant exudes hormone-like flavonoid compounds to attract Rhizobium Live intracellularly Chemotactic to roots Fig. 30.14 & Fig. 11.21 ALPHAPROTEOBACTERIA (cont.) BETAPROTEOBACTERIA Nitrifying Bacteria Nitrobacter (Nitrosomonas and others are in other groups of the proteobacteria) Purple Nonsulfur Bacteria • use anoxygenic photosynthesis • but can sometimes be chemoheterotrophs Important groups: • Neisseriales - Neisseria - gonorrhea, some meningitis • Bordetella - whooping cough Other members of this order (Burkholderiales) have a sheath GAMMAPROTEOBACTERIA • largest group of Proteobacteria • many familiar genera - Escherichia, Salmonella, Pseudomonas • incredibly diverse • Colorless sulfur bacteria - Thiobacillus GAMMAPROTEOBACTERIA (cont.) GAMMAPROTEOBACTERIA (cont.) Purple Sulfur Bacteria Pseudomonas • motile - polar flagella • usually anaerobes • photosynthetic (anoxygenic) • oxidize H2S to S0 (and sometimes S0 to SO42-) 1) Involved in mineralization - taking organic compounds back to inorganic substances. 2) Useful model organisms e.g. Pseudomonas aeruginosa (also an opportunistic pathogen, esp. in CF patients and burn victims see next slide..). GAMMAPROTEOBACTERIA (cont.) Vibrios • some are important pathogens, e.g. Vibrio cholerae Fig. 26.7 • some Vibrio (and Photobacterium) species are capable of bioluminescence These bacteria can live symbiotically with squid or fish (Fig. 11.26). Pseudomonas aeruginosa - plate shows diffusing green fluorescent pigment (a siderophore). Bottom shows polar, monotrichous flagellum. Very top is too gross to show in class - green discolored skin on a burn patient. Enzyme luciferase is involved same as in fire flies GAMMAPROTEOBACTERIA (cont.) Enterobacteria (grouped together because they are found intestines) • look similar - metabolic properties are useful in classification - flow charts • contains many common bacteria - E. coli, Salmonella, etc. DELTAPROTEOBACTERIA Two main groups: 1) Predatory bacteria: bdellovibrios and myxobacteria 2) Sulfate- and sulfur-reducing bacteria The Life Cycle of Bdellovibrio Fig. 11.25 DELTAPROTEOBACTERIA (cont.) DELTAPROTEOBACTERIA (cont.) Myxobacteria Myxospores are dessication resistant - may survive up to 10 years! • soil bacteria • complex life cycle Fig. 11.18 • most are micropredators or scavengers secrete digestive enzymes that lyse cells of yeast and other bacteria Communal living may allow them to digest prey more efficiently (wolf pack as opposed to lone predator like Bdellovibrio) • many produce antibiotics DELTAPROTEOBACTERIA (cont.) Sulfate- and Sulfur-reducing Bacteria • use these sulfur compounds as electron acceptors - anaerobic respiration EPSILONPROTEOBACTERIA • Smallest of 5 proteobacteria groups • 2 important genera: • Desulfovibrio > Campylobacter • Desulfuromonas > Helicobacter • Important in sulfur cycle in nature • Helicobacter pylori cause ulcers (will discuss more later…. Fig. 30.12 Campylobacter - some are pathogens