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Prokaryotes
Chapter 27
Where Are We Going?
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Adaptations of prokaryotes
Diversity of prokaryotes
Ecological Impact of prokaryotes
Importance to humans
Organismal Domains
Prokaryotes
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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
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Disease causing agents are
pathogens
Can live without the other
Eukaryotes
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10-100 um in size
Membrane bound nucleus
and organelles
DNA arranged on
multiple chromosomes
Can’t live without
prokaryotes
Gram Staining
Medicinally used to determine type of bacteria causing
infection
 Bacteria can be gram (+) or gram (-)
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(+) simple walls with thicker peptidoglycan, sugar polymer joined by
polypeptides
(-) more complex walls with less peptidoglycan and lipopolysaccharide
outer layer
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Make them more threatening, toxic, and resistant to antibiotics which
prevent synthesis of peptidoglycan which inhibits cell wall growth
External Prokaryotic Adaptations
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Cell wall (previously discussed)
Come in a variety of shapes
Multiple methods for adhesion
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Capsule: polysaccharide or protein
Fimbriae: hair-like protein structures
Sex pili: pull cells together before DNA
transfer
Prokaryote Adaptations
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Motility
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Internal organization
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Directional movement often made possible by flagella
Exhibit taxis, movement to or from a stimuli
Simpler than eukaryotes = no organelles
1/1000 as much DNA in the nucleoid region
Accessory rings of DNA or plasmids
Reproduction and adaptation
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Reproduce asexually by binary fission
Can form endospores when conditions unfavorable
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Water removed and metabolism halts
Genetic Diversity in Prokaryotes
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Exhibit wide range of adaptations and variation
3 factors determine
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Rapid reproduction
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Reproduce by binary fission, not sexually
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Mutation
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Rare for a particular gene
Genetic recombination
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Most offspring identical, some changes likely
Transformation, transduction, and conjugation
Combine 1st two and get genetic diversity and rapid evolution
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Fit individuals survive and reproduce more prolifically than less fit
Transformation
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Genotype (some
phenotype) altered by
uptake of foreign DNA
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Harmless strains
transformed to virulent
when placed in dead
virulent cell medium
Forms a recombinant cell
Frederick Griffith
experiment from 2107
Transduction
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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
Conjugation
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Genetic material
transferred between 2
connected cells
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Sex pili form bridge
One way process
Often is beneficial
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Antibiotic resistance or
other tolerance
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
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Oxygen
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Obligate aerobes use O2 for cellular respiration
Obligate anaerobes are poisoned by O2
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Use fermentation or anaerobic respiration
Facultative anaerobes use O2 if present, but can use
alternate methods
Nitrogen
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Eukaryotes limited in available nitrogen
Prokaryotes use nitrogen fixation to convert N2 (nitrogen
gas) to NH3 (ammonia)
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Necessary to produce AA’s
Increases nitrogen for plant usage
Biofilms
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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
Prokaryotic Diversity
Archaea
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Live where other organisms
can’t survive
Extreme halophiles
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Extreme thermophiles
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Salt environments
E.g Great Salt Lake, Dead Sea,
or seawater evaporating
ponds
Very hot water
E.g ocean vents, or acidic
conditions
Methanogens
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Anaerobic environments with
methane as a waste product
E.g. swamps and GI tracts of
animals
Proteobacteria
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Gram-negative
Both aerobic and anaerobic species
5 subgroups
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Alpha: Live in root nodules to fix atmospheric nitrogen
Beta: Nitrogen cycling
Gamma: Photosynthetic and inhabit animal intestines
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Delta: Can form fruiting bodies for selves when food is
scarce and attack other bacteria
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E.g Salmonella, Vibrio cholerae, and Escheria coliDelta:
E.g myxobacteria and Bdellovibrios
Epsilon: pathogenic to humans or other animals
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E.g Campylobacter and Helicobacter pylori
Other Prokaryotes
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Chlamydias
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Spirochetes
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Only survive within animal
cells
Gram (-), but lack
peptidoglycan
Spiral through environments
by rotating internal filaments
E.g Treponema pallidum
(syphilis) and Borrelia
burgdorferi (Lyme disease)
Cyanobacteria
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Oxygen-generating
photosynthesis (only bacteria)
Food for freshwater and
marine ecosystems
Gram-Positive Bacteria
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Actinomycetes
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Streptomyces
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Cultured as sources of antibiotics
Bacillus anthracis
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2 species responsible for tuberculosis and leprosy
Most are free-living decomposers, leave ‘earthy’ odor of soil
Forms endospores
Clostridium botulinum
Staphylococcus
Streptococcus
Mycoplasmas
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Lack cell walls and are tiniest cells
Free-living soil bacteria, but some are pathogens
Ecological Interactions
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Central role in symbiosis, where 2 species live close
Formed between larger host organism and themselves
(symbiont)
Types of interactions can vary
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Mutualism
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Commensalism
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both species benefit
one species benefits while other is unchanged
Parasitism
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parasite eats cellular components
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Usually harm, but not kill
Pathogens are the parsites that cause disease
Bacterial Poisons
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Exotoxins are proteins secreted by bacteria
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Can exist in the bacteria or without
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Vibrio cholerae releases Cl- to gut and water follows
Clostridium tetani produces muscle spasms (lockjaw)
Staphylococcus aureus common on skin and in nasal passages
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Produces several types causing varying problems
Acquired from genetic transfer between species
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E. coli benign resident of intestines
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Acquires genes that produce harmful effects
Endotoxins are components of gram (-) outer membranes
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Released when cell dies or digested by defensive cell
Cause same general symptoms
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Neisseria meningitidis (bacterial meningitis) and Salmonella (typhoid
fever)
Research and Technology
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Convert milk into cheese
and yogurt
Principle agents in
bioremediation
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Use organisms to remove
pollutants
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Oil clean up
Sewage treatment
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Solid sludge from filters
added to anaerobe colonies
Transformed into use for
fertilizer or landfill
Liquid waste over biofilms
remove organic material