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 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 StainingMedicinally used to determine type of bacteria
causing infectionBacteria 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 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
transfer
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 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
Transformation 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
Transduction 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 Genetic material
transferred between 2 connected cells Sex pili form bridge
One way process Often is beneficial
Antibiotic resistance orother 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 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 to convert N2
(nitrogen gas) to NH3 (ammonia) Necessary to produce AA’s Increases nitrogen for plant usage
Biofilms 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
ArchaeaLive where other
organisms can’t surviveExtreme 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 conditionsMethanogens
Anaerobic environments with methane as a waste product
E.g. swamps and GI tracts of animals
Proteobacteria 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 Chlamydias
Only survive within animal cells
Gram (-), but lack peptidoglycan
Spirochetes Spiral through
environments by rotating internal filaments
E.g Treponema pallidum (syphilis) and Borrelia burgdorferi (Lyme disease)
Cyanobacteria Oxygen-generating
photosynthesis (only bacteria)
Food for freshwater and marine ecosystems
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 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 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 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