Prokaryotes and the Origins of Metabolic Diversity

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Chapter 27

• Prokaryotes and the Origins of Metabolic Diversity

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Kingdom Monera

• ex bacteria, blue-green bacteria
• characteristics
• -prokaryotic
• -unicellular (some aggregates or simple
  multiforms)
• -1st organisms (by 2 bill. yrs.)
• -most numerous pervasive of life forms
• -most are benign many are essential to all
  life
• (decomposing recycling)

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The three domains of life
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Cell structure

• 3 common shapes
• 1) coccus sphere
• 2) bacillus rod
• 3) spirillum spiral
• monoploid genome which is circular dsDNA
• in nucleoid region

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Bacterial shapes
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Cell structure

• genophore prokaryotic chromosome
• very little protein associated with DNA
• plasmids smaller DNA rings each made of a
  few genes
• -allow antibiotic resistance

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Cell structure

• Not compartmentalized by endomembranes
• plasma membrane may be invaginated to create
  internal membrane surface for specialized
  functions

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Invaginations of cell membrane
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Cell structure

• Cell wall present protect, shape, prevent
  osmotic bursting
• -made of peptidoglycan (not cellulose)
• unique polymers of modified sugars cross-
• linked with short polypeptides
• Gram staining used to ID bacteria
• Gram simpler walls w/ lots of peptidoglycan
• Gram less peptidoglycan, more complex
  structure

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Gram - vs. Gram bacteria
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Cell structure

• Some have capsules which they secrete
• (additional protection adherence to
  substrates)
• pili surface appendages for adherence to
  substrates, reproduction, colony formation

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Pili
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Locomotion

• axial filaments (bundles of fine fibrils)
• cause cells to spiral
• slime secreted, then bacteria glide on it
• flagella all over surface, or concentrated at
• both ends
• taxis movement toward/away from stimulus
• (directed movement)

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Bacterial flagella
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Reproduction

• asexually binary fission splitting in 2
• sexually conjugation sex pili form to
  exchange genetic info.
• transduction (viral) virus
• carries part of bacterial NA to new
• cell

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Conjugation
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Growth limits

• exponential
• limits are due to lack of nutrients in
  environment, too much waste created, etc.

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Metabolism Nutrition

• autotrophic
• chemotrophic
• phototrophic
• heterotrophic
• chemoheterotrophic (most organisms)
• photoheterotrophic
• aerobic
• anaerobic obligate or facultative

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Diversity

• Phylum Eubacteria true bacteria
• -contemporary prokaryotes
• 1) Cyanobacteria photoautotrophs
• (blue-green
  bacteria)
• -may be filamentous
• -motile forms glide
• -freshwater (fw), saltwater (sw), damp
  soil
• -chlorophyll a (as in plants) in
  thylakoids
• -heterocysts in some useful for N2
  fixation

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Heterocysts
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Heterocysts
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Diversity

• 2) Phototrophic bacteria green purple sulfur
• -get electrons from H2S (not H2O)
• -pigment is bacteriochlorophyll
• usu. anaerobic
• 3) Pseudomonads soil, aquatic
• -most versatile chemoheterotrophs
• (may use pesticides or other synthetic
  cmpds.)

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Cyanobacteria
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Diversity

• 4) Spirochetes helical shaped corkscrew
• movement
• -large cells
• -saprophytic parasitic
• -ex Treponema pallidum cause syphilis
• Borrelia burgdorferi cause Lyme
  disease

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Leptospira, a spirochete
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Diversity

• 5) Endospore-forming bacteria
• -produce spores dehydrated cells with
  thick
• walls survive harsh conditions
• -autoclave necessary to kill spores up to
  120
• degrees C
• -ex Clostridium botulinum
• 6) Enteric inhabit intestinal tracts (may be
• normal flora)
• -ex E. coli, Salmonella typhi (pathogenic
• enteric)

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Anthrax endospore
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Diversity

• 7) Rickettsias Chlamydias very small
• (dependent parasites) (non-gonococcal
  urethritis
• most common STD in US)
• 8) Mycoplasmas smaller than rickettsias only
• prokaryotes lacking cell walls

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Chlamydias
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Mycoplasmas
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Diversity

• 9) Actinomycetes colonial resembling fungal
• bodies (once thought to be fungi)
• -causes TB leprosy
• -dirt smell in soil
• -Streptomyces produce streptomycin, other
• antibiotics

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Streptomyces
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Diverstiy

• 10) Myxobacteria gliding bacteria
• -elaborate colonies secrete slime
• -erects bulbous stalk (fruiting body)
• -spore producing brightly colored

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Myxobacteria fruiting bodies
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Diversity

• Phylum Archaebacteria ancient bacteria
• -cell walls lack peptidoglycan
• -lipid cell membrane unique enzymes
• -live in extreme environments (as in early
  Earth)
• -sewage decomposers (model systems for
• solar energy conversion) methanogens CO2
• reduced to CH4, anaerobes pink scum
• halophiles saline environment (Dead Sea)
• thermoacidophiles hot, acidic 60 80C
  pH 2-4
• (Yellowstone)

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Pink scum from extreme halophiles
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Importance

• 1) decomposers (along w/ fungi) recycle for
• ecosystems
• 2) fix N2 CO2, generate O2

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Importance

• 3) symbiotic relationships
• (symbiont smaller, inside host)
• mutualism both benefit (,)
• ex bacteria legume roots for N2
  fixation,
• vaginal bacteria keep pH in
  check, suppressing yeast
• commensalism symbiont benefits, host
• unaffected (, 0)
• parasitism symbiont benefits at hosts
  expense (, -)

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Importance

• 4) pathogens
• by
• opportunistic when defense weakens
• responsible for ½ of human diseases
• ex Streptococcus pneumonia (in
  throats)

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Importance

• Robert Koch (pronounced coke) linked
• disease to specific bacteria
• father of bacteriology
• -to ID pathogen to specific disease, use
• Kochs postulates

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Importance

• Kochs postulates
• 1) find same pathogen in each diseased
  individual
• 2) isolate pathogen from diseased subject
  grow in
• pure culture
• 3) induce disease in experimental animal by
• inoculation from culture
• 4) isolate same pathogen from exp. animal
  after
• disease develops
• true for most pathogens, few exceptions

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Importance

• or by
• exotoxins proteins secreted by bacterial cells
• (among most potent poisons known)
• -produce specific symptoms
• or
• endotoxins components of outer membranes
• of Gram bacteria
• -produce aches, fever

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Lyme disease transmitted by deer tick
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Importance

• 5) used in lab research, sewage treatment,
• food/drug industry, recombinant DNA
• technology

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Sewage treatment
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Bioremediation
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Evolution of metabolism

• -1st prokaryotes were probably chemoheterotrophs
• absorbing ATP
• -glycolysis evolved to generate ATP anaerobically
• -electron transport chemiosmosis evolved from
• transmembrane pumps once used to regulate
• internal pH in an acidic env.
• -photosynthetic proks. used light photosystems to
• fix CO2
• -1st cyanobacteria made org. cmpds. from H2O
• CO2, releasing O2
• -accumulation of O2 caused extinction of many
  proks.

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