Micro303Lecture11 - Microbiology 303 Fall 2012 Lecture 11 Cell structures II The cell wall is very important Fewer solutes Lots of solutes Water enters

Micro303Lecture11 - Microbiology 303 Fall 2012 Lecture 11...

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Unformatted text preview: Microbiology 303 Fall 2012 Lecture 11 Cell structures II The cell wall is very important Fewer solutes Lots of solutes Water enters and cell swells OsmoCc pressure The cell wall protects the cell from lysis Osmosis = movement of water across a barrier to equalize concentraCon Most bacteria have a cell wall PepCdoglycan is unique to Bacteria Sugar polymers (glycan) encircling cell Connected by crosslinking pepCdes (pepCdo) shown here as arrows Also known as sacculus, murein, cell wall NAM= M = N ­acetylmuramic acid NAG = G = N ­acetylglucosamine DAP = diaminopimelic acid PepCdoglycan synthesis is complex Penicillin binding proteins Sauvage et al 2008 FEMS Microbiol. Rev 32: 234 ­258 Lysozyme targets pepCdoglycan present in tears, saliva, milk, mucus The Gram ­posiCve cell Cell Wall Glycopolymers Roles of Cell Wall Glycopolymers Staphylococcus aureus CWG shown here Weidenmaier and Peschel, 2008. Nature Reviews Microbiology 6, 276 ­287 Cell wall ­anchored proteins: Sortase Ton-That H et al. PNAS 1999;96:12424-12429 The Gram ­negaCve cell The outer membrane Lipopolysaccharide (LPS) •  Lipid A •  NAG, not glycerol •  Core oligosaccharide varies a bit between species •  contains ketodeoxyoctanoate (KDO), a sugar unique to LPS •  O polysaccharide varies tremendously Porins Surface layer proteins are common Beveridge and Sleytr, 1999. Trends Microbiol.7: 253 ­260. S ­layer proteins Cell wall diversity •  Bacteria –  Some don’t have PG (e.g. Chlamydia, Planctomycetes) –  Mollicutes lack cell wall alltogether –  Mycobacteria have a unique cell wall •  Archaea –  All lack PG, some have pseudoPG –  Some lack cell wall (e.g. Thermoplasma) –  Some have OM Cell wall diversity: Mycoplasma •  Firmicute lineage that has lost capability to make pepCdoglycan •  Pleiomorphic cells •  Host ­associated – live in isotonic environment •  Tough cell membranes forCfied with host ­derived sterols •  Mycoplasma genitalium •  Mycoplasma pneumoniae •  Also commensal species Cell wall diversity: mycobacteria •  In the AcCnobacteria lineage •  DisCnct lipids and polysaccharides •  Many hydrophobic components Cell wall diversity: mycobacteria •  MOM? •  Mycobacterial outer membrane •  May explain cell surface hydrophobicity, resistance to anCmicrobials, etc Kaur et al 2009 Advances in Applied Microbiology 69:23–78 Cell staining Cell wall architecture ClassificaCon Archaeal cell walls: many possibiliCes Albers and Meyer Nature Reviews Microbiology 9, 414 ­426 (June 2011) Outside the cell: Cell polysaccharides capsular polysaccharide (CPS), extracellular polysaccharide (EPS), glycocalyx, slime, capsule, K anCgen, cell surface glycoconjugate HydraCon ProtecCon Afachment Example: E. coli Commercial uses of polysaccharides •  Xanthan gum –  Produced by Xanthomonas campestris –  Highly viscous even at low concentraCon and stable to variaCons in pH, temperature and electrolytes –  Used in the food industry for jams, sauces, icings, salad dressing, etc –  Used industrially in explosives, texCles, paints, mortar, oil well spacer fluids, rust removers, petroleum recovery –  Also in phamaceuCcals and cosmeCcs •  Also alginates, dextrans, cellulose, hyaluronic acid used for food and medical purposes (Cssue scaffolds, drug delivery) Other types of capsules Cell surrounded by capsule Bacillus anthracis and some other Firmicutes produce a polyglutamic acid capsule EssenCal for pathogenesis of B. anthracis Mucoid colony Producing capsule Outside the cell: Pili and fimbriae protein filaments Movement ProtecCon Afachment Pili are complex structures Type I pili Type IV pili can retract Flagella •  Appendages for moClity •  Also may be for adhesion •  Several arrangements –  Polar –  Lophotrichous –  Peritrichous Flagellar moCon: rotary moCon Jarrell and McBride 2008 Nat Rev Microbiol 6, 466 ­476 Flagellar assembly Spirochete flagella are located in the periplasm can move through very viscous environments Swarming Swimming Twitching Gliding Type IV pili Swarming moClity Proteus mirabilis Gliding moClity M. mobile cenCpede Jarrell and McBride 2008 Nat Rev Microbiol 6, 466 ­476 Miyata 2010 Annual Review of Microbiology Vol. 64: 519 ­537 MoClity symbiosis Mixotricha paradoxa Advantages of moClity: taxis •  Chemotaxis  ­ movement along a chemical gradient •  Phototaxis  ­ response to light •  Energy taxis  ­ response to sCmuli that affect cellular energy level Chemotaxis in E. coli Chemotaxis opCons Measuring chemotaxis Basic microbial features help other organisms recognize microbes •  Plants and animals have pafern recogniCon receptors (PRRs) that recognize essenCal microbial features •  In humans, Toll ­like receptor proteins (TLRs) and Nod proteins recognize microbial features to iniCate the immune response Do you recognize? Endotoxin •  •  •  •  Major factor in disease Mostly due to lipid A Can be lethal “Immune detecCon of lipid A is so sensiCve and robust that a bloodstream infecCon can cause a severe complicaCon called endotoxic shock — a major clinical problem that leads to about 200,000 deaths in the United States each year.” ...
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