Lecture 16 - Lecture 16 The Background Biology of Bacteria...

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Lecture 16: The Background Biology of Bacteria Stomatolites - Thought to be the first bacteria however evidence has arisen that they might not be real - They’re actually remains of when cyanobacteria mat together and excrete calcium Gram + and Gram – Bacteria - Gram +: thicker cell wall and teichoic acids o they stay purple after being washed with acetone o they have a thick peptidoglycan layer over the cell membrane - Gram –: endotoxin called Lipopolysaccharide (LPS) and a thinner cell wall than gram + o Lose color after being washed with acetone and appear pink when counter stained with neutral red Characteristic Features of Bacteria and Archaea vs. Eukaryotes: - Bacteria and archaea LACK membrane bound organelles and have a single circular chromosome - Bacteria and archaea LACK spliceosomal introns - Archaea and eukaryotes have multiple complex RNA polymerases and begin translation with methionine while bacteria begin translation with formyl methionine Unique features of Archaea - Cell walls vary but ALWAYS lack the peptidoglycan of bacterial cell walls - The lipids in their membranes are branched and have ether linkage to glycerol - Presences of large signal recognition RNA Types of Intron - Spliceosomal introns (nuclear introns) o Spliced by a spliceosome (proteins and RNA) o Only found in higher eukaryotes - Protein spliced introns o Found in rRNA and tRNA genes - Self-splicing introns (Groups I, II, and III) o Use the autocatalytic properties of RNA to splice o Found in scattered mitochondria, chloroplasts, bacteria and protist eukaryotes Biodiversity of Bacteria - Size of Bacteria: surface area to volume is 3:1 - Shapes of Bacteria: o Coccus: chain = streptoccus and cluster = staphylococcus o Bacillus: chain is stephobacillus o Coccbacillus o Vibrio = curved o Spirillum o Spirochete o Square o Star - Bacillus (Endobacteria) o Cell wall, mesosome, ribosomes, respiratory membranes, nucleod Bacterial Structures: o Flagella, pili, capsule, plasma membrane, cytoplasm, cell wall, lipopolysaccharides, teichoic acids, inclusions, spores Flagella - Determine motility – movement - Swarming occurs with some bacteria o Most evident in proteus species - Arrangement basis for classification o Monotrichous: 1 flagella o Lophotrichous: tuft at end o Amphitrichous: both ends o Peritrichous: all around bacteria Pili - Short protein appendages that are smaller than flagella - Adhere bacteria to surfaces and have antibodies working to block adherence - F-pilus used in conjugation which is a form of bacterial recombination - Flotation: increases buoyancy because there is more oxygen on surface
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Bacterial Cell Membrane - Bilayer phospholipid - Water can penetrate the cell membrane - Flexible - NOT strong and ruptures easily: osmotic pressure created by cytoplasm Bacterial Cell Wall - Composed of peptidoglycan polymer - Unique to bacteria - Sugars are NAG and NAM o N-acetylglucosamine o N-acetyuaramic acid - D-Form of Amino acids used not L-form o Hard to break down D form - Amino acids cross link NAG and NAM
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Lecture 16 - Lecture 16 The Background Biology of Bacteria...

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