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