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Morphology of Prokaryotic Cells: Cell Shapes
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Morphology of Prokaryotic Cells: terminology in practice Curved rods: –Campylobacter species –Vibrio species Spiral rods: –Helicobacter species –Spirillum species –Spirochetes: Leptospirosa species
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Morphology of Prokaryotic Cells: Cell Groupings
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**Bacterial Structures** You should know what all of the structures on this diagram are - what their basic composition is and what their function is
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The Glycocalyx: Capsules and Slime Layers Outermost layer Polysaccharide or polypeptide May allow cells to adhere to a surface Contributes to bacterial virulence by preventing phagocytosis An important virulence factor
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Filamentous Protein Appendages Escherichia coli Enterococcus faecium
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Rotate like a propeller Proton motive force used for energy Presence/arrangement can be used as an identifying marker Flagella - motility E. coli O157:H7
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Flagella - motility Presence/arrangement can be used as an identifying marker Peritrichous Polar Other (ex. tuft on both ends) Rotate like a propeller Proton motive force used for energy Chemotaxis - Directed movement towards/away from a chemical
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Pili - attachment Common pili (fimbriae); singular = pilus Function in adhesion = virulence factor Helical arrangement of protein subunits Sex pili - Conjugation Sharing of mobile genetic information – plasmids
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Cell Wall Provides rigidity to the cell (prevents it from bursting)
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Cell Wall Provides rigidity to the cell (prevents it from bursting)
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**Cell Wall** Peptidoglycan - rigid molecule; unique to bacteria Glycan chains are connected to each other via peptide chains on NAM molecules Alternating subunits of NAG and NAM form glycan chains Know the basic structure/composition of the bacterial cell wall; know the structureal and chemical differences between the cell walls of Gram-negative and Gram-positive bacteria and how these differences relate to how they appear in a Gram stained slide
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Cell Wall
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Medical significance of peptidoglycan Target for selective toxicity; synthesis is targeted by certain antimicrobial medications (penicillins, cephalosporins) Recognized by innate immune system Target of lysozyme (in egg whites, tears)
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Cell Wall Gram-positive Thick layer of peptidoglycan Teichoic acids
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Cell Wall Gram-negative Thin layer of peptidoglycan Outer membrane - additional membrane barrier Lipopolysaccharide (LPS) O antigen Core polysaccharide Lipid A
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Cell Wall Gram-negative Thin layer of peptidoglycan Outer membrane - additional membrane barrier; porins permit passage lipopolysaccharide (LPS) endotoxin - recognized by innate immune system - ex. E. coli O157:H7
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Cell Wall Gram-negative Thin layer of peptidoglycan Outer membrane - additional membrane barrier; porins permit passage lipopolysaccharide (LPS) periplasm
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Cytoplasmic membrane Defines the boundary of the cell Transport proteins function as selective gates (selectively permeable) Control entrance/expulsion of antimicrobial drugs Receptors provide a sensor system Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules Phospholipid bilayer, embedded with proteins
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The Gram stain
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Acid fast stains: Fite’s, modified Fite’s, Kinyoun Primary stain: carbolfuchsin Decolorizing agent: acid alcohol Secondary stain: methylene blue
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Defines the boundary of the cell Transport proteins function as selective gates (selectively permeable) Control entrance/expulsion of antimicrobial drugs Receptors provide a sensor system Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules Phospholipid bilayer, embedded with proteins Cytoplasmic membrane
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Defines the boundary of the cell Transport proteins function as selective gates (selectively permeable) Control entrance/expulsion of antimicrobial drugs Receptors provide a sensor system Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules Phospholipid bilayer, embedded with proteins
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Cytoplasmic membrane Defines the boundary of the cell Transport proteins function as selective gates (selectively permeable) Control entrance/expulsion of antimicrobial drugs Receptors provide a sensor system Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules Phospholipid bilayer, embedded with proteins Fluid mosaic model
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Electron transport chain - Series of proteins that eject protons from the cell, creating an electrochemical gradient Proton motive force is used to fuel: Synthesis of ATP (the cell’s energy currency) Rotation of flagella (motility) One form of transport Cytoplasmic membrane Electron transport chain
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If a function of the cell membrane is transport….. How is material transported in/out of the cell? –Passive transport No ATP Along concentration gradient –Active transport Requires ATP Against concentration gradient
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Types of transport Passive transport Simple diffusion Facilitated diffusion Osmosis Active transport System that uses proton motive force System that uses ATP Group translocation
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Facilitated Diffusion
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Diffusion of water is Osmosis
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Active transport: Proton Motive Force
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Active transport: Use ATP
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Active transport: Group translocation
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Internal structures: Chromosome
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Internal structures: Ribosomes
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Internal structures:Storage Granules
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Internal structures: Cytoskeleton
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Internal structures: Endospores
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