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1 Dr. Alvin Fox External layers of vegetative cells and spores, Lecture 27
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2 KEY WORDS Cell envelope Teichoic acid Cell wall Teichuronic acid Cell membraneLipoteichoic acid Outer membrane Mycolic acid Peptidoglycan Undecaprenol (bactoprenol) Braun lipoprotein Endospore (spore) Porins Cell division Lipopolysaccharide
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3 Topics: Structure of vegetative cell envelopesStructure of vegetative cell envelopes –unique cell envelope molecules –biosynthesis of cell wall constituents Endospores (dormant cells) Endospores (dormant cells) Cell divisionCell division
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4 Cell Envelope ell membrane + cell wall (+ plus outer membrane) Cell membrane + cell wall (+ plus outer membrane) Cell wall Cell wall – peptidoglycan – attached structures
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5 Bacterial cell envelopes Gram stain (+ or -) correlates with structure
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6 Gram positive Gram negative
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7 Peptidoglycan single macromolecule single macromolecule highly cross-linked highly cross-linked surrounds cell surrounds cell provides rigidity provides rigidity
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8 Peptidoglycan glycan backbone –muramic acid –glucosamine peptide side chain peptide cross-bridge (or direct peptide bond) –D- and L- amino acids – sometimes diaminopimelic acid
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9 Muramic acid, D-amino acids diaminopimelic acid – not synthesized by mammals
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10 Peptidoglycan Example with direct peptide bond Muramic acid Glucosamine L-alanine D-glutamic acid L-lysine/Diaminopimelic acid D-alanine
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11 Gram Positive Cell Envelope Teichoic acid –polymer –ribitol phosphate or ribitol glycerol backbone – Teichuronic acid –polymer –no phosphorus –glucuronic acid
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12 Teichoic and teichuronic acids Metal ion uptake Direct autolytic enzymes –holes punched in cell wall –allows insertion cell wall (synthesis)
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13 Lipoteichoic acids cell membrane autolysins kept from cell wall
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14 Gram Positive Cell Envelope r Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane
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15 Braun lipoproteinBraun lipoprotein –binds cell wall to outer membrane Gram Negative Peptidoglycan
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16 Outer Membrane lipopolysaccharidelipopolysaccharide phospholipidsphospholipids ProteinsProteins –porins
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17 Lipopolysaccharide Lipid A Glucosamine disaccharide Beta hydroxy fatty acids Core Heptoses Ketodeoxyoctonic acid O-antigen Highly variable n
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18 Inner (cytoplasmic) membrane Outer Membrane Lipopolysaccharide Porin Braun lipoprotein Gram Negative Cell Envelope Peptidoglycan
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19 rrr rr r Acid Fast Cell Envelope rrrr Peptidoglycan-arabinogalactan-mycolic acid Cytoplasmic membrane Mycolic acid lipids
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20 Peptidoglycan synthesis Cytoplasm Cell wall undecaprenol sugar aminoacid Cell Membrane 123
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21 Lipopolysaccharide synthesis similar to peptidoglycan also on undecaprenol carrier
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22 Spore Modified Gram positive bacteria cellModified Gram positive bacteria cell – unusual cell envelope cell membranecell membrane outer membraneouter membrane
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23 Spore Peptidoglycan layer Peptidoglycan layer – cortex – between two membranes – less cross-linked – dehydrated muramic acid (lactam)
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24 Vegetative cell division Sporulation
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25 cortex The endospore exosporium coat Innermembrane outermembrane
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