prokaryotes(chapter 27)

a) most unicellular

some species gather together

sometimes temporarily

can form colonies

even division of labor by specialized cell types

prokaryote structure . . .

prokaryote structure . . . b) shapes

cocci (spheres)diplococci - pairsstreptococci - chainsstaphylococci - grape-like clusters

bacillirods

helical (spirochetes)spiral shaped

prokaryote structure . . . c) sizes

1-5 μm vs. 10-100 μm

largest prokaryote is 0.75 mm (750 μm!)

d) cell wall

nearly all possess

3 functionsmaintains cell shapeprovides physical protectionprevent lysing in hypotonic environment

prokaryote structure . . .

most pathogens

unique to prokaryotes (except Archaea)

e) motility

about 1/2 of prokaryotes exhibit

methodsflagella

most commonunique structurespirochetes move through helical filaments

under cell wall attached to motorslimy threads

secreted by bacteriaadhere to substrate

prokaryote structure . . .

prokaryote flagellum . . .

prokaryotic taxis . . . taxis = movement towards or away from a stimulus (taxi)

chemotaxisreceptor cells on bacterial surface sense

environmental chemicals

phototaxisrespond to lightimportant for photosynthetic species

geotaxistaxis associated with magnetic fieldse.g. orientation towards nutrient-rich lake bottom

f) cell components

anuclear

no internal compartmentalizationuse infolded regions of membrane

simple genome~1/1000 as much DNA as eukaryotessingle loop in nucleoid region

possess plasmidsaccessory loops of DNA with few genesprovide for

antibiotic resistancespecial contingencies

replicate independent of main genomecan be passed to partner

prokaryote structure . . .

no meiosis . . . so no gene mixing . . . but do have

prokaryote reproduction . . .

transformationabsorption/integration of fragments of DNA

from environmentcan occur across species lines

conjugationone cell transfers genes to

anothertransduction

virus as vector

can form endospores . . .

Bacillus anthracis

prokaryotic metabolism . . .

unique to prokaryotes

H2S, NH3, Fe2+

obligate aerobesrequire O2

prokaryotes and oxygen . . .

facultative anaerobesuse O2 if present

can also engage in fermentation

obligate anaerobes

O2 poisons them

prokaryotes and nitrogen . . .

~5,000 species known could be as high as 400,000 to 4 million!

prokaryotic systematics . . .

comparing the 3 domains . . .

prokaryotic diversity . . .

domain Archaea . . . great diversity in extreme habitatsunique characteristicsno peptioglycan in cell wallsextremophiles3 classifications

methanogensenergy by using CO2 to oxidize H2strictest of anaerobesfound in swamps and marshes

where other organisms have depleted O2important in herbivore digestionproduce methane

halophiles“love” salty places (halo - salt)

e.g. Great Salt Lake, Dead Seaothers tolerate, some must have

thermophiles“love” hot places (thermo - heat)optimum temperature for most is 60-80 Ce.g. hotsprings of Yellowstone, geothermal vents

o

halophiles . . .

thermophiles . . . Beggiatoa

prokaryotic diversity . . .

domain Bacteria . . .clade Proteobacteria

all gram negativealphaclosely related with eukaryotic hosts as symbionts or parasites; nitrogen fixers

betanitrogen fixers

gammasulfur bacteria; E. coli

deltaMyxobacteria forms colonies;Bdellovibrio predatory (can move up to 100 μm/sec [~220 mph] when attacking prey!)

epsiloncause of some stomach ulcers

domain Bacteria . . .chlamydiassurvival dependent upon animal host cells

spirochetesmany free-living, but . . . e.g. Treponema pallidium (syphilis) Borrelia burgdorferi (Lyme disease)

gram-positivesAll gram positive bacteria here;colonial - actinomycetes

e.g. Streptomycessolitary

e.g. Bacillus anthracis (anthrax)endospores

Clostridium botulinum (botulism)endosporesfatal toxin (1 g can kill 106 humans!)

cyanobacteriaonly prokaryotes who photosynthesizelike eukaryotes

e.g. Anabaena

Anabaena

cyanobacteria (our friends) . . .Gloeothece

FischerellaCalothrix

Nostoc

prokaryotes & ecology. . .

bioremediation. . .

prokaryotes gone bad (the pathogens) . . .

Pus smear (wound)Staphylococcus aureus

C. botulinum

Sputum smearStreptococcus pneumoniae

Left: Neisseria gonorrhoeae Gram stain of pure culture; Right: Neisseria gonorrhoeae Gram stain of a pustularexudate.

exotoxins - secreted by the prokaryotecan be problem even if organism not present

e.g. botulism caused by endotoxin ofC. botulism

endotoxins - components of outer membrane of some gram negative bacteria

e.g. Salmonella

Haemophilus influenzae

Lyme disease caused by Borrelia burgdorferi

Treponema pallidium (syphilis)

Bacillus anthracis (anthrax)