Ch 27 Prokaryotes Domain Bacteria Domain Archaebacteria Domain

Ch. 27 Prokaryotes Domain Bacteria Domain Archaebacteria Domain Bacteria 2007 -2008 Domain Archaea Common ancestor Domain Eukarya

Bacteria live EVERYWHERE! • Bacteria live in all ecosystems – on plants & animals – in the soil – in depths of the oceans – in extreme cold – in extreme hot – in extreme salt – on the living – on the dead Microbes always find a way to make a living!

Bacterial diversity Rods(bacilli) and spheres(cocci) and spirals(helical)…Oh My!

Prokaryote Structure • Unicellular – bacilli, cocci, spirilli • Size – 1/10 size of eukaryote cell • 1 micron (1 um) • Internal structure – no internal compartments • no membrane-bound organelles • only ribosomes – circular chromosome, naked DNA • not wrapped around proteins prokaryote cell eukaryote cell

mitochondria Variations in Cell Interior cyanobacterium (photosythetic) bacterium aerobic bacterium chloroplast inter n for p al membr h a like a otosynthe nes s (thyl chloropla is akoid st s) nes a r b em m l a n inter piration rion d es for r mitochon like a e) a (crist

Prokaryote Cell Wall Structure Gram-positive bacteria peptide side chains cell wall peptidoglycan plasma membrane protein That’s peptidoglycan = polysaccharides + amino acid chains important for lipopolysaccharides = lipids + polysaccharides your doctor to know! outer membrane of Gram-negative bacteria lipopolysaccharides cell wall outer membrane peptidoglycan plasma membrane

Motility • 1 - Flagella • 2 - Helical shape (spirochetes) • 3 - Slime • 4 -Taxis (movement away or toward a stimulus)

Form & Function • Nucleoid region (genophore: noneukaryotic chromosome) • Plasmids • Asexual reproduction: binary fission (not mitosis) • “Sexual” reproduction (not meiosis): • transformation~ uptake of genes from surrounding environment • conjugation~ direct gene transfer from 1 prokaryote to another transduction~ gene transfer by viruses • Endospore: resistant cells for harsh conditions (250 million years!)

Genetic variation in bacteria • Mutations – bacteria can reproduce every 20 minutes • binary fission – error rate in copying DNA • 1 in every 200 bacteria has a mutation • you have billions of E. coli in your gut! – lots of mutation potential! • Genetic recombination – bacteria swap genes • plasmids – small supplemental circles of DNA • conjugation – direct transfer of DNA

Nutrition & Metabolism • Photoautotrophs: photosynthetic; harness light to drive the synthesis of organics (cyanobacteria) • Chemoautotrophs: oxidation of inorganics for energy; get carbon from CO 2 • Photoheterotrophs: use light to generate ATP but get carbon in an organic form • Chemoheterotrophs: consume organic molecules for both energy and carbon – saprobes- dead organic matter decomposer – parasites- absorb nutrients from living hosts • Oxygen relationships: obligate aerobes; facultative anaerobes; obligate anaerobes

Bacteria as pathogens – animal diseases • tooth decay, ulcers • anthrax, botulism • plague, leprosy, “flesheating” disease • STDs: gonorrhea, chlamydia • typhoid, cholera • TB, pneumonia • lyme disease plant diseases • wilts, fruit rot, blights opportunistic: normal residents of host; cause illness when defenses are weakened • Koch’s postulates: criteria for bacterial disease confirmation • exotoxins: bacterial proteins that can produce disease w/o the prokaryote present (botulism) • endotoxins: components of gram membranes (Salmonella)

Bacteria as beneficial (& necessary) • Life on Earth is dependent on bacteria – decomposers • recycling of nutrients from dead to living – nitrogen fixation • only organisms that can fix N from atmosphere – needed for synthesis of proteins & nucleic acids – plant root nodules – help in digestion (E. coli) • digest cellulose for herbivores – cellulase enzyme • produce vitamins K & B 12 for humans – produce foods & medicines • from yogurt to insulin