Prokaryote Lifestyle

Prokaryote Lifestyle • 1) rapidly reproducing cells: 1-3 h • 20-50 minutes/generation in E. coli • deep soil bacteria: 70-100 years! (1000 yrs) • 2) tremendous growth if: • enough nutrients • not poisoned by metabolic waste • 3) adaptation to changing environment

Example of sharing plasmid: Microbes in Dry Valleys of Antarctica • harsh conditions, slow growth • UV, dry, windy, metals • gen. time 100 days • live within rock • 1/3 strains resistant to chromium, metals • new strains get plasmid with genes for resistance

diversity of prok. in soils • sequencing study • pH is most critical factor • neutral soils most diverse • Peruvian rainforest acidic, less diversity

Examples of Quorum Sensing • flashlight fish (Fig 27.20) • Vibrio fischeri • mutualism (both benefit) • cholera • Vibrio cholerae • parasitism (parasite eats host) • pathogen (parasite causes disease) • exotoxin secreted • Idea: instead of antibiotics, stop communication

Endotoxins from gram negative bacteria: lipopolysaccharides released when cell dies Fig 27.3, p 557

Swarming • coordinated, rapid movement • cover solid surface • eg. Rhizobium etli

complex behavior • Myxobacteria • mxyo = slime • when no nutrients • swarm, aggregate • release spores • huge genome

Biofilms • community w/complex structure • lose flagella, excrete matrix • polysaccharides, proteins, nucleic acids • diverse, resistant • examples • medical implants, ships hulls • dental plaque, cow’s rumen

human microbiome • body is ecosystem. many symbioses • mostly commensalism, mutualism • 500—1000 species of bacteria • 10x as many bacterial as human cells • unique combination of prokaryotes • diversity: skin, gut (mouth-> intestines) • Bacteroides thetaiotaomicron • Helicobacter pylori causes stomach ulcers • makes ammonia to buffer stomach acid • other chronic diseases?

problems with antibiotics • 1) disrupt native prokaryotes • make vitamins, digest food • compete with pathogens • 2) select for resistant prok. • a few w/resistance mutation survive • reproduce rapidly without competitors

prok evolve so antibiotics won’t work • Some resistant to many antibiotics: • Mycobacterium tuberculosis (prisons) • methicillin resistant Staph. aureus (hosp) • Antibiotics in environment: waste from humans & factory farm animals • good news: revert quickly without

how to minimize problem • take antibiotics only when necessary • use bleach: true antibacterial—acts like cannon (antibiotic has specific target) • avoid “antibacterial” products incl. triclosan • soaps, toothpaste, socks, cutting boards • wash hands with ordinary soap • avoid alcohol-based soapless cleaners & too much hand washing • remove oils (natural defense)

Application: genetic engineering with Agrobacterium • Infects plants w/plasmid (Fig 20.25) • introduce genes • (eg. resistance to virus) • ecological consideration: • unintended results? • Bacillus thuringiensis Bt toxin • insecticide • requires gut bacteria in insect

Methanotrophs • use methane for energy & carbon • anaerobic archaea • aerobic proteobacteria • cycle: use methane from methanogens or from underwater volcanoes • enzyme breaks down methane and 250 other compounds: bioremediation • can convert toxic waste to salt & CO2

Chemical Cycles • prok recycle nutrients: N, P, S, CH4 • parasites absorb nutrients from living hosts • saprobes absorb nutrients from dead organic matter • metabolically critical • decomposers, recyclers • decomposition of waste products & organisms

Compost: example of nutrient recycling • C (brown plants) • N (green plants) • air & water • fungi, prokaryotes • esp actinobacteria • worms, insects

Prokaryote Lifestyle