Transcript Phylogenetic Relationships

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
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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
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when no nutrients
swarm, aggregate
release spores
huge genome
complex behavior
• Myxobacteria
– mxyo = slime
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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
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– 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
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C (brown plants)
N (green plants)
air & water
fungi, prokaryotes
– esp actinobacteria
– worms, insects