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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