Transcript Prokaryotes
Prokaryotes Domain Bacteria Domain Archaebacteria Domain Bacteria AP Biology Domain Archaea Domain Eukarya 2007-2008 Common ancestor What characteristics make Archaea more like eukaryotes than prokaryotes? No peptidoglycan in cell wall More than 1 RNA polymerase Some introns Met is 1st amino acid in protein synthesis Ribosomes more like eukarytoes (Streptomycin does not kill archaea) Domain Bacteria Domain Archaea 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 Microbes always in extreme cold find a way to make a living! in extreme hot in extreme salt on the living on the dead Bacterial diversity rods and spheres and spirals eukaryote cell Prokaryote Structure Unicellular bacilli, cocci, spirilli Size 1/10 size of eukaryote cell 1 micron (1um) Internal structure: prokaryote cell Prokaryote vs. Eukaryote Chromosome Prokaryote Eukaryote double helix 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 small supplemental circles of DNA conjugation direct transfer of DNA Metabolic Relation to Oxygen How are bacteria categorized by the effect that oxygen has on growth? Obligate aerobes Facultative anaerobes Obligate anaerobes What role do prokaryotes play in nitrogen cycling? Only way that nitrogen gas can be incorporated into organic molecules mitochondria Variations in Cell Interior cyanobacterium (photosythetic) bacterium chloroplast aerobic bacterium Origins of Metabolic Diversity Heterotrophs most likely came before photoautotrophs (parsimony) Glycolysis was probably the first metabolic pathway Natural selection favored autotrophs as heterotrophs depleted food supply Cyanobacteria introduce chl a and oxygen gas. Cell Wall What are the functions of the cell wall in prokaryotes? Maintain cell shape Protection Prevent bursting in hypotonic environment Made of peptidoglycan Why is some food preserved by salting it? Hypertonic environment plasmolyzes bacterial cells Prokaryote Cell Wall Structure Gram-positive bacteria peptide side chains cell wall peptidoglycan plasma membrane That’s important for your doctor to know! protein peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides Gram-negative bacteria cell wall outer membrane of lipopolysaccharides outer membrane peptidoglycan plasma membrane Prokaryotic metabolism How do bacteria acquire their energy & nutrients? photoautotrophs photosynthetic bacteria chemoautotrophs oxidize inorganic compounds nitrogen, sulfur, hydrogen… heterotrophs live on plant & animal matter decomposers & pathogens Disease Disease – exotoxins release poisons such as botulism and cholera Endotoxins seen in outer membrane of gram neg. bacteria (Salmonella) What are Koch’s postulates and why are they important? Koch’s postulates used to isolate pathogen causing disease Bacteria as pathogens Disease-causing microbes plant diseases wilts, fruit rot, blights animal diseases tooth decay, ulcers anthrax, botulism plague, leprosy, “flesh-eating” disease STDs: gonorrhea, chlamydia typhoid, cholera TB, pneumonia lyme disease Bacteria as beneficial (& necessary) Life on Earth is dependent on bacteria recycling of nutrients from dead to living 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 Germinating akinetes Got any Questions?? Ask da’ Boss! QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. AP Biology 2007-2008 Gram positive Are these bacteria Gram + or Gram –? Gram negative