交大微生物课件lecture3-3microbial cell biology原核胞壁肽聚糖与相关分子

Lecture3-3:MicrobialcellbiologyCellStructureandShanghaiJiaoTongUniversity3.8CellWallofProkaryotes:PeptidoglycanandRelated原核生物胞壁:肽聚糖与相关Fig4.32 ((b)Inasolutioncontaininganisotonicconcentrationofa(suchassucrose,waterdoesnotenterthe stand remainsstable.等渗溶液中,水不进入原 ,原 稳定WhatisacellwallAwallisforagainstpressure-2atmAwallisformaintainingcellshapeAwallisforgivingcellsrigidityShanghaiJiaoTongGramstain革兰氏染Thisstainingmethodhaslongbeenusedforclassifyingandidentifyingbacteria(Formoredetail:Lecture3-1)ShanghaiJiaoTongFig4-4StepsintheGramstainprocedure.ExamplesofGramDifferencesinDifferencesincellwallstructureareatthebaseofdifferencesintheGram-stainingreaction.TheG-cellwallisamultilayeredstructureandquitecomplex,whereastheG+cellwallconsistsofprimarilyasingletypeofmoleculeandisoftenmuchthicker.Fig4.27Fig4.27CellwallsofPeptidoglycanCellwallofBacteriahaveonerigidlayertostrengthenthewall.TherigidlayerofGandGBacteriaispeptidoglycanlayer.肽聚糖层InG-Bacteria,additionallayersarepresentoutsidethisrigidlayer.ShanghaiJiaoTongPeptidoglycanunitPeptidoglycanunitiscomposedoftwosugerderivatives,N-acetylglucosamineandN-acetylmuramicacidandasmallgroupofaminoacidsconsistingofL-alanine,D-alanine,D-glutamicacid,andeitherlysineordiaminopimelicacid(DAP).肽聚糖由N-乙酰葡萄糖胺和-乙酰胞壁酸两种糖,加上一组氨基酸组成(DAP:二氨基庚二酸 Fig (c)(c)OverallstructureofG,N-acetylglucosamine;M,N-acetylmuramicFig4-30Howthepeptideandglycanunitsareconnectedtoformthepeptidoglycansheet.(a)Nointerbridgeingram-negativeBacteria.(b)Glycineinterbridgeingram-positiveBacteria.G+菌的肽聚糖单位之间有甘氨酸五肽桥,而G-菌无五肽桥ThestructureofGrampositivebacterialcellwallsOnethickpeptidoglycanlayer(25sheets)Teichoicacids（磷壁酸）PolymerscontainingglycerolphosphateorribitolLipoteichoicacidsteichoicacidsthatcovalentlyboundtomembranelipids脂磷壁酸:与膜脂类共价连接的磷壁酸ShanghaiJiaoTongFig.Fig.4.31Summarydiagramofthegram-positivecellThecellwallsofgram-positivecellscontainmostlypeptidoglycan.Thecellwallsofgram-positivecellsaresmootherthanthatofgram-negativecells.4.9TheOuterMembraneofGramNegativeBacteriaTwomembranesOutermembrane Oneoutofcellboundedspace ShanghaiJiaoTongFig4.35Thegram-negativecellwall.Althoughtheoutermembraneisoftencalledthe"secondFig4.35Thegram-negativecellwall.Althoughtheoutermembraneisoftencalledthe"secondlipidbilayer,"thechemistryandarchitectureofthislayerdiffersinmanywaysfromthatofthe smicmembraneShanghaiJiaoTongStructureofthelipopolysaccharide(LPS)ofGbacteria.•O-specificpolysaccharidevariesamongspecies.O-•Core •LipidA类脂ShanghaiJiaoTongFig4.36CellwallofG—bacteriaunderelectronFig4.27ThesurfacetextureofaG-cellisheavilyfoldedwhencomparedwithaG+RelationshipofCellWallStructuretotheGramStain Phenomenon:InGramstain,aninsolublecrystalviolet-iodinecomplexisformedinsidethecell,andthecomplexisextractedbyalcoholfromG-butnotfromG+Bacteria.Reason:G+Bacteria,whichhaveverythickpeptidoglycan edehydratedbythealcohol.Thiscausestheporesinthewallstoclose,preventingtheinsolublecrystalviolet-iodinecomplexfromesca.G+菌的厚肽聚糖层被乙醇脱水,造成壁上小孔收缩,从而使不溶性的结晶Then,whathappenedtoG-Bacteria?ShanghaiJiaoTongShanghaiJiaoTongInG-Bacteria,alcoholreadilypenetratesthelipid-richouterlayer,andthethinpeptidoglycanlayeralsodoesnotpreventsolventpassage,thus,thecrystalviolet-iodinecomplexiseasilyremoved.G-菌中,乙醇很容易 外膜,薄的肽聚糖壁也无 ShanghaiJiaoTongHowcancellwall ethetargetforkillingacell?PeptidoglycanStructureLysozyme:-1,4bondissensitiveto肽聚糖的-1,4PeptidoglycansynthesisPenicillinThefirstcommercializedandstillmostimportantantibiotic青霉素ShanghaiJiaoTongTransportofpeptidoglycanprecursorswassendtothegrowingpointofthecellwallacrossthecyto smicmembraneThetranspeptidationreactionthatleadstothefinalcross-linkingoftwopeptidoglycanchains转肽作用PenicillinandPenicillininhibitoroftranspeptidationCreateimbalancebetwe