基礎(chǔ)微生物學(xué)課件公開課一等獎(jiǎng)?wù)n件省課獲獎(jiǎng)?wù)n件

微生物吸取營養(yǎng)物質(zhì)方式第1頁1、單純擴(kuò)散(simplediffusionorpassivediffusion)被輸送物質(zhì)，靠細(xì)胞內(nèi)外濃度為動力，以透析或擴(kuò)散形式從高濃度區(qū)向低濃度區(qū)擴(kuò)散。Simplediffusionmeansthatthemoleculescanpassdirectlythroughthemembrane.Diffusionisalwaysdownaconcentrationgradient.Thislimitsthemaximumpossibleconcentrationofthemoleculeinsidethecell(oroutsidethecellifitisawasteproduct).Theeffectivenessofdiffusionisalsolimitedbythediffusionrateofthemolecule.Therefore,thoughdiffusionisaneffectiveenoughtransportmechanismforsomesubstances(suchasH2O),thecellmustutilizeothermechanismsformanyofitstransportneeds.第2頁1、單純擴(kuò)散(simplediffusionorpassivediffusion)特點(diǎn)：①擴(kuò)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(xì)胞膜中含水小孔，由高濃度胞外環(huán)境向低濃度胞內(nèi)擴(kuò)散；②在擴(kuò)散過程中營養(yǎng)物質(zhì)構(gòu)造不發(fā)生變化：即既不與膜上分子發(fā)生反應(yīng)，本身分子構(gòu)造也不發(fā)生變化；③物質(zhì)運(yùn)輸速率較慢：速率與胞內(nèi)外營養(yǎng)物質(zhì)濃度差有關(guān)，即隨細(xì)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(kuò)散是一種不需要代謝能運(yùn)輸方式：因此，物質(zhì)不能進(jìn)行逆濃度運(yùn)輸。⑤可運(yùn)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(kuò)散模式圖細(xì)胞膜外細(xì)胞膜內(nèi)細(xì)胞膜第5頁三營養(yǎng)物通過與細(xì)胞膜上載體蛋白（也稱作透過酶permease）可逆性結(jié)合來加快其傳遞速度促進(jìn)擴(kuò)散

(facilitateddiffusion/transport)Facilitateddiffusionutilizesmembraneproteinchannelstoallowchargedmolecules(whichotherwisecouldnotdiffuseacrossthecellmembrane)tofreelydiffuseinandoutofthecell.ThesechannelscomesintogreatestusewithsmallionslikeK+,Na+,andCl-.Thespeedoffacilitatedtransportislimitedbythenumberofproteinchannelsavailable,whereasthespeedofdiffusionisdependentonlyontheconcentrationgradient.第6頁促進(jìn)擴(kuò)散(facilitateddiffusion)特點(diǎn)：在促進(jìn)擴(kuò)散過程中營養(yǎng)物質(zhì)本身在分子構(gòu)造上也不會發(fā)生變化不消耗代謝能量，故不能進(jìn)行逆濃度運(yùn)輸運(yùn)輸速率由胞內(nèi)外該物質(zhì)濃度差決定需要細(xì)胞膜上載體蛋白（透過酶）參與物質(zhì)運(yùn)輸被運(yùn)輸物質(zhì)與載體蛋白有高度特異性養(yǎng)料濃度過高時(shí),與載體蛋白出現(xiàn)飽和效應(yīng)促進(jìn)擴(kuò)散運(yùn)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P(yáng)roteins

thatactascarriers

aretoolargetomoveacrossthemembrane.Theyaretransmembraneproteins.Theycyclebetweentwoconformationsinwhichasolutebindingsiteisaccessibleononesideofthemembraneortheother.第10頁促進(jìn)擴(kuò)散模式圖細(xì)胞膜細(xì)胞膜外細(xì)胞膜內(nèi)恢復(fù)原構(gòu)象移位再循環(huán)結(jié)合結(jié)合構(gòu)象變化第11頁oractiveansport

第12頁積極運(yùn)輸(Activetransport)在代謝能推進(jìn)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(yùn)輸(Activetransport)特點(diǎn)：物質(zhì)在積極運(yùn)輸過程中需要消耗代謝能能夠進(jìn)行逆濃度運(yùn)輸運(yùn)輸方式需要載體蛋白參與對被運(yùn)輸物質(zhì)有高度立體專一性被運(yùn)輸物質(zhì)在轉(zhuǎn)移過程中不發(fā)生任何化學(xué)變化不一樣微生物在積極運(yùn)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(xué)能，光合微生物中則主要來自光能。積極運(yùn)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(yùn)輸模式圖細(xì)胞膜細(xì)胞膜外細(xì)胞膜內(nèi)恢復(fù)原構(gòu)象移位再循環(huán)結(jié)合構(gòu)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(xì)胞內(nèi)“泵”出胞外,并將K+“泵”入胞內(nèi)。該酶由大小兩個(gè)亞基組成（MW:12萬,5.5萬）第18頁作用步驟:1.ATP酶(E)在細(xì)胞內(nèi)側(cè)與3個(gè)Na+結(jié)合,同步消耗能量;2.磷酸化ATP酶(E+)構(gòu)象變化將Na+排除胞外,并與2個(gè)K+

結(jié)合;3.K+激發(fā)E+脫磷酸化恢復(fù)為E,同步將K+運(yùn)入細(xì)胞.第19頁第20頁

基因轉(zhuǎn)位是一種特殊積極運(yùn)輸，與一般積極運(yùn)輸相比，營養(yǎng)物質(zhì)在運(yùn)輸過程中發(fā)生了化學(xué)變化（糖在運(yùn)輸過程中發(fā)生了磷酸化）。其他特點(diǎn)與積極運(yùn)輸相同?；蜣D(zhuǎn)位主要存在于厭氧和兼性厭氧型細(xì)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(yùn)輸基團(tuán)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(yùn)輸機(jī)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(yùn)輸步驟:1.熱穩(wěn)載體蛋白(HPr)激活

細(xì)胞內(nèi)高能化合物磷酸烯醇式丙酮酸（PEP）磷酸基團(tuán)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(jié)合在細(xì)胞膜上，具有高能磷酸載體作用。第23頁2、糖被磷酸化后運(yùn)入膜內(nèi)膜外環(huán)境中糖先與外膜表面酶2結(jié)合，再被轉(zhuǎn)運(yùn)到內(nèi)膜表面。這時(shí)，糖被P-HPr上磷酸激活，并通過酶2作用將糖-磷酸釋放到細(xì)胞內(nèi)。酶2

P-HPr+糖糖-P+HPr酶2是一種結(jié)合于細(xì)胞膜上蛋白，它對底物具有特異性選擇作用，因此細(xì)胞膜上可誘導(dǎo)出一系列與底物分子對應(yīng)酶2。第24頁基團(tuán)移位模式圖細(xì)胞膜外細(xì)胞膜內(nèi)SSSS細(xì)胞膜Enz2Enz2Enz2Enz2SSHPrP~PHPr~Enz1+PEP丙酮酸第25頁四種運(yùn)輸營養(yǎng)物質(zhì)方式比較比較項(xiàng)目單純擴(kuò)散促進(jìn)擴(kuò)散積極運(yùn)輸基團(tuán)轉(zhuǎn)位特異載體蛋白運(yùn)輸速度物質(zhì)運(yùn)輸方向胞內(nèi)外濃度運(yùn)輸分子能量消耗運(yùn)輸后物質(zhì)構(gòu)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