Transcript Chapter 27
Chapter 27 Prokaryotes and the Origins of Metabolic Diversity Eukaryote Classification Old 5 Kingdom system • Monera, Protists, Plants, Fungi, Animals Prokaryote New 3 Domain system – reflects a greater understanding of evolution & molecular evidence • Prokaryote: Bacteria • Prokaryote: Archaebacteria • Eukaryotes – Protists – Plants – Fungi – Animals Archaebacteria & Bacteria Prokaryotes Domain Bacteria Domain Archaebacteria Domain Bacteria Domain Archaea 2007-2008 Common ancestor Domain Eukarya Bacteria live EVERYWHERE! Bacteria live in all ecosystems – – – – – – – – – on plants & animals in 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 Bacterial diversity Rods(bacilli) and spheres(cocci) and spirals(helical)…Oh My! eukaryote cell Prokaryote Structure prokaryote cell Unicellular – bacilli, cocci, spirilli Size – 1/10 size of eukaryote cell • 1 micron (1um) Internal structure – no internal compartments • no membrane-bound organelles • only ribosomes – circular chromosome, naked DNA • not wrapped around proteins mitochondria Variations in Cell Interior cyanobacterium (photosythetic) bacterium chloroplast aerobic bacterium 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) QuickTime™ and a Cinepak decompressor are needed to see this picture. Form & Function Nucleoid region (genophore: non-eukaryotic 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 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 CO2 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 decomposers 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, “flesh-eating” disease • STDs: gonorrhea, chlamydia • typhoid, cholera • TB, pneumonia • lyme disease 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 & B12 for humans – produce foods & medicines • from yogurt to insulin