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Prokaryotes. Chapter 27. Where Are We Going?. Adaptations of prokaryotes Diversity of prokaryotes Ecological Impact of prokaryotes Importance to humans. Organismal Domains. Prokaryotes. Eukaryotes. 1-5 um in size (10 fold diff.) 10X’s more biomass Wider range of environments

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Chapter 27

where are we going
Where Are We Going?
  • Adaptations of prokaryotes
  • Diversity of prokaryotes
  • Ecological Impact of prokaryotes
  • Importance to humans
organismal domains
Organismal Domains



  • 1-5 um in size (10 fold diff.)
  • 10X’s more biomass
  • Wider range of environments
  • Greater diversity
  • Single, circular chromosome
  • Best known as bacteria
    • Disease causing agents are pathogens
  • Can live without the other
  • 10-100 um in size
  • Membrane bound nucleus and organelles
  • DNA arranged on multiple chromosomes
  • Can’t live without prokaryotes
gram staining
Gram Staining
  • Medicinally used to determine type of bacteria causing infection
  • Bacteria can be gram (+) or gram (-)
      • (+) simple walls with thicker peptidoglycan, sugar polymer joined by polypeptides
      • (-) more complex walls with less peptidoglycan and lipopolysaccharide outer layer
        • Make them more threatening, toxic, and resistant to antibiotics which prevent synthesis of peptidoglycan which inhibits cell wall growth
external prokaryotic adaptations
External Prokaryotic Adaptations
  • Cell wall (previously discussed)
  • Come in a variety of shapes
  • Multiple methods for adhesion
    • Capsule: polysaccharide or protein
    • Fimbriae: hair-like protein structures
    • Sex pili: pull cells together before DNA


prokaryote adaptations
Prokaryote Adaptations
  • Motility
    • Directional movement often made possible by flagella
    • Exhibit taxis, movement to or from a stimuli
  • Internal organization
    • Simpler than eukaryotes = no organelles
    • 1/1000 as much DNA in the nucleoid region
    • Accessory rings of DNA or plasmids
  • Reproduction and adaptation
    • Reproduce asexually by binary fission
    • Can form endospores when conditions unfavorable
      • Water removed and metabolism halts
genetic diversity in prokaryotes
Genetic Diversity in Prokaryotes
  • Exhibit wide range of adaptations and variation
  • 3 factors determine
    • Rapid reproduction
      • Reproduce by binary fission, not sexually
        • Most offspring identical, some changes likely
    • Mutation
      • Rare for a particular gene
    • Genetic recombination
      • Transformation, transduction, and conjugation
    • Combine 1st two and get genetic diversity and rapid evolution
      • Fit individuals survive and reproduce more prolifically than less fit
  • Genotype (some phenotype) altered by uptake of foreign DNA
    • Harmless strains transformed to virulent when placed in dead virulent cell medium
  • Forms a recombinant cell
  • Frederick Griffith experiment from 2107
  • Bacteriophages carry bacterial genes from one host to another
  • Lack machinery to be able to reproduce
  • Infect bacteria (1) and incorporate their DNA into new bacteriophages
  • Bacteriophages that result then repeat with new mixed DNA
  • Genetic material transferred between 2 connected cells
    • Sex pili form bridge
  • One way process
  • Often is beneficial
    • Antibiotic resistance or

other tolerance

nutritional adaptations
Nutritional Adaptations

Prokaryotes categorized based on how energy and carbon are obtained

Gr: plants and algae

Ylw: certain prokaryotes

Pur: marine prokaryotes and halophiles

Bl: most prokaryotes, protists, fungi, animals, and some plants

prokaryotic metabolism
Prokaryotic Metabolism
  • Oxygen
    • Obligate aerobes use O2 for cellular respiration
    • Obligate anaerobes are poisoned by O2
      • Use fermentation or anaerobic respiration
    • Facultative anaerobes use O2 if present, but can use alternate methods
  • Nitrogen
    • Eukaryotes limited in available nitrogen
    • Prokaryotes use nitrogen fixation toconvert N2 (nitrogen gas) to NH3 (ammonia)
      • Necessary to produce AA’s
      • Increases nitrogen for plant usage
  • Secrete signaling molecules to recruit nearby cells and grow
  • Produce proteins to stick to self and substrates
  • Nutrients in and wastes out via channels
  • Dental plaque below is an example
  • Live where other organisms can’t survive
  • Extreme halophiles
    • Salt environments
    • E.g Great Salt Lake, Dead Sea, or seawater evaporating ponds
  • Extreme thermophiles
    • Very hot water
    • E.g ocean vents, or acidic conditions
  • Methanogens
    • Anaerobic environments with methane as a waste product
    • E.g. swamps and GI tracts of animals
  • Gram-negative
  • Both aerobic and anaerobic species
  • 5 subgroups
    • Alpha: Live in root nodules to fix atmospheric nitrogen
    • Beta: Nitrogen cycling
    • Gamma: Photosynthetic and inhabit animal intestines
      • E.g Salmonella, Vibrio cholerae, and Escheria coliDelta:
    • Delta: Can form fruiting bodies for selves when food is

scarce and attack other bacteria

      • E.g myxobacteria and Bdellovibrios
    • Epsilon: pathogenic to humans or other animals
      • E.g Campylobacter and Helicobacter pylori
other prokaryotes
Other Prokaryotes
  • Chlamydias
    • Only survive within animal cells
    • Gram (-), but lack peptidoglycan
  • Spirochetes
    • Spiral through environments by rotating internal filaments
    • E.gTreponemapallidum(syphilis) and Borreliaburgdorferi(Lyme disease)
  • Cyanobacteria
    • Oxygen-generating photosynthesis (only bacteria)
    • Food for freshwater and marine ecosystems
gram positive bacteria
Gram-Positive Bacteria
  • Actinomycetes
    • 2 species responsible for tuberculosis and leprosy
    • Most are free-living decomposers, leave ‘earthy’ odor of soil
  • Streptomyces
    • Cultured as sources of antibiotics
  • Bacillus anthracis
    • Forms endospores
  • Clostridium botulinum
  • Staphylococcus
  • Streptococcus
  • Mycoplasmas
    • Lack cell walls and are tiniest cells
    • Free-living soil bacteria, but some are pathogens
ecological interactions
Ecological Interactions
  • Central role in symbiosis, where 2 species live close
  • Formed between larger host organism and themselves (symbiont)
  • Types of interactions can vary
    • Mutualism
      • both species benefit
    • Commensalism
      • one species benefits while other is unchanged
    • Parasitism
      • parasite eats cellular components
        • Usually harm, but not kill
        • Pathogens are the parsites that cause disease
bacterial poisons
Bacterial Poisons
  • Exotoxins are proteins secreted by bacteria
    • Can exist in the bacteria or without
      • Vibrio cholerae releases Cl- to gut and water follows
      • Clostridium tetani produces muscle spasms (lockjaw)
      • Staphylococcus aureus common on skin and in nasal passages
        • Produces several types causing varying problems
      • Acquired from genetic transfer between species
        • E. coli benign resident of intestines
          • Acquires genes that produce harmful effects
  • Endotoxins are components of gram (-) outer membranes
    • Released when cell dies or digested by defensive cell
    • Cause same general symptoms
      • Neisseria meningitidis (bacterial meningitis) and Salmonella (typhoid fever)
research and technology
Research and Technology
  • Convert milk into cheese and yogurt
  • Principle agents in bioremediation
    • Use organisms to remove pollutants
      • Oil clean up
      • Sewage treatment
        • Solid sludge from filters added to anaerobe colonies
        • Transformed into use for fertilizer or landfill
        • Liquid waste over biofilms remove organic material