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当前位置:首页 > 高等教育 > 大学课件 > 大学考研 食品专业 双语课件_Lecture_3
Lecture3-3:MicrobialcellbiologyCellStructureandFunctionSchoolofLifeScienceandBiotechnologyShanghaiJiaoTongUniversity原核生物细胞壁:肽聚糖与相关分子Protoplasts原生质体(a)Indilutesolutionbreakdownofthecellwallreleasestheprotoplast,butitimmediatelylysesbecausethecytoplasmicmembraneisveryweak.稀溶液中原生质体会立即破裂.Protoplasts原生质体(b)Inasolutioncontaininganisotonicconcentrationofasolutesuchassucrose,waterdoesnotentertheprotoplastanditremainsstable.等渗溶液中,水不进入原生质体,原生质体稳定.ShanghaiJiaoTongUniversityShanghaiJiaoTongUniversityWhatisacellwallfor?Awallisforagainstpressure-2atmAwallisformaintainingcellshapeAwallisforgivingcellsrigidityShanghaiJiaoTongUniversityShanghaiJiaoTongUniversityGramstain革兰氏染色Thisstainingmethodhaslongbeenusedforclassifyingandidentifyingbacteria(Formoredetail:Lecture3-1)StepsintheGramstainprocedure.革兰氏染色过程结晶紫染1分钟碘液媒染3分钟酒精脱色20秒沙黄复染1-2分钟FLASHExamplesofGramStainingDifferencesincellwallstructureareatthebaseofdifferencesintheGram-stainingreaction.TheG-cellwallisamultilayeredstructureandquitecomplex,whereastheG+cellwallconsistsofprimarilyasingletypeofmoleculeandisoftenmuchthicker.CellwallsofBacteriaFLASHShanghaiJiaoTongUniversityShanghaiJiaoTongUniversity4.8.1Peptidoglycan肽聚糖CellwallofBacteriahaveonerigidlayertostrengthenthewall.TherigidlayerofG+andG-Bacteriaispeptidoglycanlayer.肽聚糖层InG-Bacteria,additionallayersarepresentoutsidethisrigidlayer.Peptidoglycanunitiscomposedoftwosugerderivatives,N-acetylglucosamineandN-acetylmuramicacid,andasmallgroupofaminoacidsconsistingofL-alanine,D-alanine,D-glutamicacid,andeitherlysineordiaminopimelicacid(DAP).肽聚糖由N-乙酰葡萄糖胺和-乙酰胞壁酸加上一组氨基酸组成(DAP:二氨基庚二酸)Howthepeptideandglycanunitsareconnectedtoformthepeptidoglycansheet.(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.(c)Overallstructureofpeptidoglycan.G,N-acetylglucosamine;M,N-acetylmuramicacid4.8.2ThestructureofGrampositivebacterialcellwallsOnethickpeptidoglycanlayer(25sheets)Teichoicacids(磷壁酸)•Polymerscontainingglycerolphosphateorribitolphosphateresidues含在磷酸甘油及磷酸核糖醇的多聚物•Lipoteichoicacids:teichoicacidsthatcovalentlyboundtomembranelipids脂磷壁酸:与膜脂类共价连接的磷壁酸Thecellwallsofgram-positivecellscontainmostlypeptidoglycan.Thecellwallsofgram-positivecellsaresmootherthanthatofgram-negativecells.ShanghaiJiaoTongUniversityShanghaiJiaoTongUniversity4.9TheOuterMembraneofGramNegativeBacteriaTwomembranes•Outermembrane外膜•Cytoplasmicmembrane细胞质膜Onethinpeptidoglycanlayer一层肽聚糖层Periplasmspace周质空间•OneoutofcellboundedspacePorinAlthoughtheoutermembraneisoftencalledthesecondlipidbilayer,thechemistryandarchitectureofthislayerdiffersinmanywaysfromthatofthecytoplasmicmembraneThegram-negativecellwall.ShanghaiJiaoTongUniversityShanghaiJiaoTongUniversityStructureofthelipopolysaccharide(LPS)ofG-bacteria.脂多糖•O-specificpolysaccharidevariesamongspecies.O-特异多糖•Corepolysaccharide核心多糖•LipidA类脂AThesurfacetextureofaG-cellisheavilyfoldedwhencomparedwithaG+cell.ShanghaiJiaoTongUniversityShanghaiJiaoTongUniversityRelationshipofCellWallStructuretotheGramStainPhenomenon:InGramstain,aninsolublecrystalviolet-iodinecomplexisformedinsidethecell,andthecomplexisextractedbyalcoholfromG-butnotfromG+Bacteria.Reason:G+Bacteria,whichhaveverythickpeptidoglycanlayer,becomedehydratedbythealcohol.Thiscausestheporesinthewallstoclose,preventingtheinsolublecrystalviolet-iodinecomplexfromescaping.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紫-碘复合物不能洗出.Then,whathappenedtoG-Bacteria?ShanghaiJiaoTongUniversityShanghaiJiaoTongUniversityInG-Bacteria,alcoholreadilypenetratesthelipid-richouterlayer,andthethinpeptidoglycanlayeralsodoesnotpreventsolventpassage,thus,thecrystalviolet-iodinecomplexiseasilyremoved.G-菌中,乙醇很容易穿透富脂的外膜,薄的肽聚糖壁也无法阻止溶剂的通过.ShanghaiJiaoTongUniversityShanghaiJiaoTongUniversityHowcancellwallbecomethetargetforkillingacell?PeptidoglycanStructure•Lysozyme:β-1,4glycosidicbondissensitivetolysozyme肽聚糖的β-1,4糖苷链对溶菌酶敏感Peptidoglycansynthesis•Penicillin:Thefirstcommercializedandstillmostimportantantibiotic青霉素Transportofpeptidoglycanprecursorswassendtothegrowingpointofthecellwallacrossthecytoplasmicmembrane细菌萜醇Thetranspeptidationreactionthatleadstothefinalcross-linkingoftwopeptidoglycanchains转肽作用ShanghaiJiaoTongUniversityShanghaiJiaoTongUniversityPenicillinandlysozymePenicillin•inhibitoroftranspeptidation抑制转肽作用•Createimbalancebetweentheactionofautolysinandtranspeptidation造成自溶与转肽作用的不平衡•CanonlykillactivelygrowingcellsLysozyme•Breakexisitingglycosidicbonds•Leadtocellburst•CreateprotoplastorspheroplastShanghaiJiaoTongUniversityShanghaiJiaoTongUniversity
本文标题:大学考研 食品专业 双语课件_Lecture_3
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