prokaryotes - fd.valenciacollege.edufd.valenciacollege.edu/file/sclark/prokaryotes (27).pdf ·...
TRANSCRIPT
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)