基礎微生物學課件公開課一等獎課件省課獲獎課件

微生物吸取營養(yǎng)物質(zhì)方式第1頁1、單純擴散(simplediffusionorpassivediffusion)被輸送物質(zhì)，靠細胞內(nèi)外濃度為動力，以透析或擴散形式從高濃度區(qū)向低濃度區(qū)擴散。Simplediffusionmeansthatthemoleculescanpassdirectlythroughthemembrane.Diffusionisalwaysdownaconcentrationgradient.Thislimitsthemaximumpossibleconcentrationofthemoleculeinsidethecell(oroutsidethecellifitisawasteproduct).Theeffectivenessofdiffusionisalsolimitedbythediffusionrateofthemolecule.Therefore,thoughdiffusionisaneffectiveenoughtransportmechanismforsomesubstances(suchasH2O),thecellmustutilizeothermechanismsformanyofitstransportneeds.第2頁1、單純擴散(simplediffusionorpassivediffusion)特點：①擴散是非特異性營養(yǎng)物質(zhì)吸取方式：如營養(yǎng)物質(zhì)通過細胞膜中含水小孔，由高濃度胞外環(huán)境向低濃度胞內(nèi)擴散；②在擴散過程中營養(yǎng)物質(zhì)構造不發(fā)生變化：即既不與膜上分子發(fā)生反應，本身分子構造也不發(fā)生變化；③物質(zhì)運輸速率較慢：速率與胞內(nèi)外營養(yǎng)物質(zhì)濃度差有關，即隨細胞膜內(nèi)外該物質(zhì)濃度差減少而減小，直到胞內(nèi)外物質(zhì)濃度相同；④不需要載體參與；

擴散是一種不需要代謝能運輸方式：因此，物質(zhì)不能進行逆濃度運輸。⑤可運輸養(yǎng)料有限：限于水、溶于水氣體，及分子量小，脂溶性、極性小營養(yǎng)物質(zhì)。第3頁smosisflowstowardshighsaltconcentrations第4頁單純擴散模式圖細胞膜外細胞膜內(nèi)細胞膜第5頁三營養(yǎng)物通過與細胞膜上載體蛋白（也稱作透過酶permease）可逆性結合來加快其傳遞速度促進擴散

(facilitateddiffusion/transport)Facilitateddiffusionutilizesmembraneproteinchannelstoallowchargedmolecules(whichotherwisecouldnotdiffuseacrossthecellmembrane)tofreelydiffuseinandoutofthecell.ThesechannelscomesintogreatestusewithsmallionslikeK+,Na+,andCl-.Thespeedoffacilitatedtransportislimitedbythenumberofproteinchannelsavailable,whereasthespeedofdiffusionisdependentonlyontheconcentrationgradient.第6頁促進擴散(facilitateddiffusion)特點：在促進擴散過程中營養(yǎng)物質(zhì)本身在分子構造上也不會發(fā)生變化不消耗代謝能量，故不能進行逆濃度運輸運輸速率由胞內(nèi)外該物質(zhì)濃度差決定需要細胞膜上載體蛋白（透過酶）參與物質(zhì)運輸被運輸物質(zhì)與載體蛋白有高度特異性養(yǎng)料濃度過高時,與載體蛋白出現(xiàn)飽和效應促進擴散運輸方式多見于真核微生物中，例如一般在厭氧生活酵母菌中，某些物質(zhì)吸取和代謝產(chǎn)物分泌是通過這種方式完成。第7頁Embededprotein:第8頁第9頁Proteins

thatactascarriers

aretoolargetomoveacrossthemembrane.Theyaretransmembraneproteins.Theycyclebetweentwoconformationsinwhichasolutebindingsiteisaccessibleononesideofthemembraneortheother.第10頁促進擴散模式圖細胞膜細胞膜外細胞膜內(nèi)恢復原構象移位再循環(huán)結合結合構象變化第11頁oractiveansport

第12頁積極運輸(Activetransport)在代謝能推進下，通過膜上特殊載體蛋白逆養(yǎng)料濃度梯度吸取營養(yǎng)物質(zhì)過程第13頁積極運輸(Activetransport)特點：物質(zhì)在積極運輸過程中需要消耗代謝能能夠進行逆濃度運輸運輸方式需要載體蛋白參與對被運輸物質(zhì)有高度立體專一性被運輸物質(zhì)在轉(zhuǎn)移過程中不發(fā)生任何化學變化不一樣微生物在積極運輸過程中所需能量起源不一樣，好氧微生物中直接來自呼吸能，厭氧微生物主要來自化學能，光合微生物中則主要來自光能。積極運輸是微生物吸取營養(yǎng)物質(zhì)主要方式。第14頁

Comparisonofpassiveandactivetransport.

Legend:Ifunchargedsolutesaresmallenough,theycanmovedowntheirconcentrationgradientsdirectlyacrossthelipidbilayeritselfbysimplediffusion.Examplesofsuchsolutesareethanol,carbondioxide,andoxygen.Mostsolutes,however,cancrossthemembraneonlyifthereisamembranetransportprotein(acarrierproteinorachannelprotein)totransferthem.Asindicated,passivetransport,inthesamedirectionasaconcentrationgradient,occursspontaneously,whereastransportagainstaconcentrationgradient(activetransport)requiresaninputofenergy.Onlycarrierproteinscancarryoutactivetransport,butbothcarrierproteinsandchannelproteinscancarryoutpassivetransport.第15頁第16頁積極運輸模式圖細胞膜細胞膜外細胞膜內(nèi)恢復原構象移位再循環(huán)結合構象變化ADP+PiATP第17頁Na+-K+-ATP酶系統(tǒng)Na+-K+-ATPase是存在于原生質(zhì)膜上一種主要離子通道蛋白功能:利用ATP能量將Na+由細胞內(nèi)“泵”出胞外,并將K+“泵”入胞內(nèi)。該酶由大小兩個亞基組成（MW:12萬,5.5萬）第18頁作用步驟:1.ATP酶(E)在細胞內(nèi)側與3個Na+結合,同步消耗能量;2.磷酸化ATP酶(E+)構象變化將Na+排除胞外,并與2個K+

結合;3.K+激發(fā)E+脫磷酸化恢復為E,同步將K+運入細胞.第19頁第20頁

基因轉(zhuǎn)位是一種特殊積極運輸，與一般積極運輸相比，營養(yǎng)物質(zhì)在運輸過程中發(fā)生了化學變化（糖在運輸過程中發(fā)生了磷酸化）。其他特點與積極運輸相同?；蜣D(zhuǎn)位主要存在于厭氧和兼性厭氧型細菌中，也主要是用于單（或雙）糖與糖衍生物，以及核苷與脂肪散運輸基團轉(zhuǎn)位(Grouptranslocation)第21頁在酶Ⅰ作用下HPr被激活在酶Ⅱ作用下P-HPr將磷酸轉(zhuǎn)移給糖第22頁運輸機制:是依靠磷酸轉(zhuǎn)移酶系統(tǒng),即磷酸烯醇式丙酮酸-己糖磷酸轉(zhuǎn)移酶系統(tǒng).運輸步驟:1.熱穩(wěn)載體蛋白(HPr)激活

細胞內(nèi)高能化合物磷酸烯醇式丙酮酸（PEP）磷酸基團把HPr激活。酶1

PEP+HPr丙酮酸+P-HPrHPr是一種低分子量可溶性蛋白，結合在細胞膜上，具有高能磷酸載體作用。第23頁2、糖被磷酸化后運入膜內(nèi)膜外環(huán)境中糖先與外膜表面酶2結合，再被轉(zhuǎn)運到內(nèi)膜表面。這時，糖被P-HPr上磷酸激活，并通過酶2作用將糖-磷酸釋放到細胞內(nèi)。酶2

P-HPr+糖糖-P+HPr酶2是一種結合于細胞膜上蛋白，它對底物具有特異性選擇作用，因此細胞膜上可誘導出一系列與底物分子對應酶2。第24頁基團移位模式圖細胞膜外細胞膜內(nèi)SSSS細胞膜Enz2Enz2Enz2Enz2SSHPrP~PHPr~Enz1+PEP丙酮酸第25頁四種運輸營養(yǎng)物質(zhì)方式比較比較項目單純擴散促進擴散積極運輸基團轉(zhuǎn)位特異載體蛋白運輸速度物質(zhì)運輸方向胞內(nèi)外濃度運輸分子能量消耗運輸后物質(zhì)構造無慢由濃至稀相等無特異性不需要不變有快由濃至稀相等特異性不需要不變有快由稀至濃胞內(nèi)濃度高特異性需要不變有快由稀至濃胞內(nèi)濃度高特異性需要變化第26頁SpecialCases1.

Endocytosis2.

Exocytosis第27頁Therearefourtypesofcarrier-mediatedtransportsystemsinprocaryotes.Thecarrierisaprotein(orgroupofproteins)thatfunctioninthepassageofasmallmoleculefromonesideofamembranetoanother.Atransportsystemmaybeasingletransmembranousproteinthatformsachannelthatadmitspassageofaspecificsolute.Oratransportsystemmaybeacoordinatedsystemofproteinsthatbindsandsequentiallypassesasmallmoleculethroughmembrane.Transportsystemshavethepropertyofspecificityforthesolutetransported.Sometransportsystemstransportasinglesolutewiththesamespecificityandkineticsasanenzyme.Sometransportsystemswilltransport(structurally)relatedmolecules,althoughatreducedefficiencycomparedtotheirprimarysubstrate.Mosttransportsystemstransportspecificsugars,aminoacids,anionsorcationsthatareofnutritionalvaluetothebacterium.第28頁Figure12.Transportprocessesinbacterialcells.Solutesenterorexitfrombacterialcellsbymeansofoneofthreeprocesses:uniport,symport(alsocalledcotransport)andantiport(alsocalledexchangediffusion).Transportsystems(Figure13below)operatebyoneoranotheroftheseprocesses.第29頁第30頁Facilitateddiffusionsystems(FD)aretheleastcommontypeoftransportsysteminbacteria.Actually,theglyceroluniporterinE.coliistheonlywellknownfacilitateddiffusionsystem.FDinvolvesthepassageofaspecificsolutethroughacarrierthatformsachannelinthemembrane.Thesolutecanmoveineitherdirectionthroughthemembranetothepointofofequilibriumonbothsidesofthemembrane.Althoughthesystemiscarrier-mediatedandspecific,noenergyisexpendedinthetransportprocess.Forthisreasontheglycerolmoleculecannotbeaccumulatedagainsttheconcentrationgradient.Facilitateddiffusionsystems(FD)第31頁Iondriventransportsystems(IDT)andBinding-proteindependenttransportsystems(BPDT)areactivetransportsystemsthatareusedfortransportofmostsolutesbybacterialcells.IDTisusedforaccumulationofmanyionsandaminoacids;BPDTisfrequentlyusedforsugarsandaminoacids.IDTisasymportorantiportprocessthatusesahydrogenion(H+)i.e.,protonmotiveforce(pmf),orsomeothercation,i.e.,chemiosmoticpotential,todrivethetransportprocess.IDTsystemssuchasthelactosepermeaseofE.coliutilizetheconsumptionofahydrogenionduringthetransportoflactose.Thustheenergyexpendedduringactivetransportoflactoseisintheformofpmf.Thelactosepermeaseisasingletransmembranouspolypeptidethatspansthemembraneseventimesformingachannelthatspecificallyadmitslactose.第32頁Binding-proteindependenttransportsystems,suchasthehistadinetransportsysteminE.coli,arecomposedoffourproteins.Twoproteinsformamembranechannelthatallowspassageofthehistadine.Athirdproteinresidesintheperiplasmicspacewhereitisabletobindtheaminoacidandpassittoaforthproteinwhichadmitstheaminoacidintothemembranechannel.Drivingthesolutethroughthechannelinvolvestheexpenditureofenergy,whichisprovidedbythehydrolysisofATP.第33頁Grouptranslocationsystems(GT),morecommonlyknownasthephosphotransferasesystem(PTS)inE.coli,areusedprimarilyforthetransportofsugars.Likebindingprotein-dependenttransportsystems,theyarecomposedofseveraldistinctcomponents.However,GTsystemsspecificforonesugarmaysharesomeoftheircomponentswithothergrouptransportsystems.InE.coli,glucosemaybetransportedbyagrouptranslocationprocessthatinvolvesthephosphotransferasesystem.Theactualcarrierinthemembraneisaproteinchannelfairlyspecificforglucose.Glucosespecificallyentersthechannelfromtheoutside,butinordertoexitintothec