lec 8 - Welcome to BSCI 207 according to Higgins...

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Unformatted text preview: Welcome to BSCI 207 according to Higgins Prokaryotes A Troubled Taxonomy! Where do we find prokaryotes? Define Prokaryote Characteristics: see Table 27.2 Figures 7.1 through 7.5 Fig 7.1 Draw the picture and tell the story Prokaryotic Features: Supercoiled DNA One or more circular chromosomes Few associated proteins Nucleoid region (vs. nucleus) Fig 7.3 Prokaryotic Genome (pages 431-2) Size of genome proportional to metabolic capabilities Tremendous diversity of genes Redundancy is common Multiple chromosomes Many small, extrachromosomal DNAs called plasmids Genome size & metabolic capabilities Mycoplasma - parasite that causes pneumonia Acquires most nutrients from the host Few enzymes, ergo few genes! E. coli & Psuedomonas Inhabits soils and humans! Synthesizes almost all organic molecules Prokaryotic Genome (pages 431-2) Size of genome proportional to metabolic capabilities Tremendous diversity of genes Many are unique to a species Redundancy within a genome is common Multiple chromosomes are not uncommon Many small, extra-chromosomal DNAs called plasmids Plasmids Small number of genes Copied independently of chromosomal DNA May or may not be necessary for growth Site of antibiotic resistance Allows for lateral transfer of genes Even among different species! Fig 20.4: Lateral Gene Transfer Thermotoga maritima Same habitats - deep sea hydrothermal vents 25% of genome shared with archaeal genome Occur in distinctive clusters in DNA Also.... Evidence for prokaryotic parasites picking up genes from eukaryotic hosts! Mechanism? ????? Fig 7.3 Fig 5.3: Review of Sugar Structure Fig 5.4a: linkage Table 5.1a: Starch Table 5.1c: Cellulose Table 5.1e: Peptidoglycan Function of cell wall: rigidity H2O High [solute] Bacterial cell Result = hydrostatic pressure for structure Summary: Characterized Prokaryotes & Eukarotes & Archaea (Table 27.2) 27.2 Note: mechanisms of generating diversity in prokaryotes Moving into Prokaryotic Diversity Morphological Metabolic Fig 7.4: Bacterial Ribosome Fig 5.5 Other Prokaryotic Characteristics Lack of compartmentalization or Organelles Little cytoskeleton Recent discovery of any cytoskeletal elements Protein FtsZ Fig 11.6: FstZ Filaments Phylogeny? Archaea? Prokaryotes but phylogenetically closer to Eukaryotes than to Bacteria Fig 27.10 Table 27.2 What the heck are the Archaea? http://www.ucmp.berkeley.edu/archaea/ archaea.html Looking for Archeae Some Archaea Dr. Carl Woese: utilized RNA sequences Table 27.2 Table 5.1e: Peptidoglycan: Bacterial Cell Walls Table 5.1c: Cellulose: Eukaryotic & some Archaea cell walls Archaea plasma membranes Fig 6.4: Membrane lipid side chains Fig 6.6: Membrane Phospholipids Fig 6.7: Membrane Phospholipids Archaea phospholipid Fig 6.4: Membrane Phospholipids Fig 6.10 Fig 6.11: Unsaturation: More Fluid & More permeable Fig 6.12 Liquid or solid? Saturation & chain length Fig 6.4: Membrane Phospholipids Table 27.2 Evolutionary Themes & Diversification of Bacteria and Archaea Morphological Diversity Metabolic Diversity Remember why the rate of evolution and the generation of diversity is high! Answer: Large number of organisms involved Short generation time i.e., many DNA replications/time Genetic redundancy Rapidly changing environment in many cases (selective pressures) Plasmids = lateral gene transfer Looking ahead... Diversity & classification Metabolic - redox reactions and electron transport Morphological diversity Environment - Structure - Function? ...
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