Chapter 27 l Prokaryotes and the Origins of Metabolic Diversity

Archaebacteria & Bacteria Classification l Old 5 Kingdom system Monera, Protists, Plants, Fungi, Animals l New 3 Domain system –reflects a greater understanding of evolution & molecular evidence Prokaryote: Bacteria Prokaryote: Archaebacteria Eukaryotes –Protists –Plants –Fungi –Animals Prokaryote Eukaryote

Prokaryotes Domain Bacteria Domain Archaebacteria Domain Bacteria Domain Archaea Domain Eukarya Common ancestor

Bacteria live EVERYWHERE! l 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!

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

Variations in Cell Interior internal membranes for photosynthesis like a chloroplast (thylakoids) internal membranes for respiration like a mitochondrion (cristae) aerobic bacterium mitochondria cyanobacterium (photosythetic) bacterium chloroplast

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

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

Form & Function l Nucleoid region (genophore: non-eukaryotic chromosome) l Plasmids l Asexual reproduction: binary fission (not mitosis) l “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 l Endospore: resistant cells for harsh conditions (250 million years!)

Genetic variation in bacteria l 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! l Genetic recombination –bacteria swap genes plasmids –small supplemental circles of DNA conjugation –direct transfer of DNA conjugation

Nutrition & Metabolism l Photoautotrophs: photosynthetic; harness light to drive the synthesis of organics (cyanobacteria) l Chemoautotrophs: oxidation of inorganics for energy; get carbon from CO2 l Photoheterotrophs: use light to generate ATP but get carbon in an organic form l Chemoheterotrophs: consume organic molecules for both energy and carbon saprobes- dead organic matter decomposers parasites- absorb nutrients from living hosts l 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) l 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