高级微生物20141020

一、细胞通讯(cellcommunication)与信号转导(signaltransduction)概述二、双组分调控系统（Two-componentregulatorysystem）三、CyclicNucleotideSecondMessengersinBacteria四、群体感应（Quorum-Sensing）微生物细胞通讯和信号转导一、细胞通讯(cellcommunication)与信号转导(signaltransduction)概述细胞通讯是细胞间或细胞内通过高度精确和高效地发送与接收信息的通讯机制，对环境作出综合反应的细胞行为。细胞信号转导细胞通过位于胞膜或胞内的受体感受胞外信息分子的刺激，经复杂的细胞内信号转导系统的转换来影响细胞的生物学功能。•《Whatispopularinresearchtoday？》——信号转导（细胞周期调控；细胞凋亡；细胞衰老；DNA损伤与修复）•美国科学情报研究所根据SCI收录及引用论文检索，全世界自然科学研究中论文发表最集中的三个领域分别——细胞信号转导,细胞凋亡,基因组与蛋白组学研究•细胞信号转导研究的3部分接收信号的特定受体受体后的信号转导通路信号的生物学效应细胞通讯的一般过程◆信号分子的产生信号分子◆细胞识别（Cellrecognition）受体蛋白◆信号转导（Signaltransduction）胞内信号特定基因表达应答反应细胞将胞外信号(分子A)转变成胞内的信号(分子B)电话接收器将电信号转换成声信号细胞通讯与信号传递引起的反应◆酶活性的变化◆基因表达的变化◆细胞骨架构型◆通透性的变化◆DNA合成活性的变化◆细胞死亡程序变化等。细胞通讯的作用●细胞间的通讯对于多细胞生物体的发生和组织的构建，协调细胞的功能，控制细胞的生长、分裂、分化和死亡是必须的。CELLCOMMUNICATIONSectionA:AnOverviewofCellSignaling1.Cellsignalingevolvedearlyinthehistoryoflife2.Communicatingcellsmaybeclosetogetherorfarapart3.Thethreestagesofcellsignalingarereception,transduction,andresponseCell-to-cellcommunicationisabsolutelyessentialformulticellularorganisms.Cellsmustcommunicatetocoordinatetheiractivities.Communicationbetweencellsisalsoimportantformanyunicellularorganisms.Biologistshavediscoveredsomeuniversalmechanismsofcellularregulation,involvingthesamesmallsetofcell-signalingmechanisms.Cellsmayreceiveavarietyofsignals:chemicalsignals,electromagneticsignals,andmechanicalsignals.IntroductionOnetopicofcell“conversation”issex.TheyeastSaccharomycescerevisiae,theyeastofbread,wine,andbeer,identifiesitsmatesbychemicalsignaling.Therearetwosexes,aandalpha,eachofwhichsecretesaspecificsignalingmolecule,afactorandalphafactorrespectively.Thesefactorseachbindtoreceptorproteinsontheothermatingtype.1.CellsignalingevolvedearlyinthehistoryoflifeOncethematingfactorshaveboundtothereceptors,thetwocellsgrowtowardeachotherandexperienceothercellularchanges.Twooppositecellsfuse,ormate.Thea/alphacellcontainsthegenesofbothcells.Theprocessbywhichasignalonacell’ssurfaceisconvertedintoaspecificcellularresponseisaseveralstepsinasignal-transductionpathway.Themoleculardetailsinbothyeastandanimalcellsarestrikinglysimilar,eventhoughtheirlastcommonancestorwasoverabillionyearsago.Signalingmoleculesevolvedfirstinancientprokaryotesandwerethenadoptedfornewusesbysingle-celledeukaryotesandmulticellulardescendents.Cellsignalinghasremainedimportantinthemicrobialworld.Myxobacteria,soil-dwellingbacteria,usechemicalsignalstocommunicatenutrientavailability.Whenfoodisscarce,cellssecreteasignaltoothercellsleadingthemtoaggregateandformthick-walledspores.Fig.11.2Individualrod-shapedcellsSpore-formingstructure(fruitingbody)AggregationinprocessFruitingbodies0.5mm132AplasmamembraneisessentialforacellItdoesisolatethecellfromitssurroundingsAcellcannotsurviveifitcannotsensechangesintheextracellularenvironmentandrespondtothemCellcommunicationistheprocessofcellsdetectingandrespondingtosignalsintheextracellularenvironmentNeededtocoordinatecellularactivitiesinamulticellularorganismOneimportantreasonforcellcommunicationistopromotecelldivisionCellcommunicationorcellsignalinginvolvesincomingandoutgoingsignalsSignalsareagentsthatinfluencethepropertiesofcellsSignalsaffecttheconformationofareceptorleadingtoaresponseinthecellWhydocellsneedtorespondtosignals?1.NeedtorespondtoachangingenvironmentAdaptationoracellularresponseiscriticalforsurvivalGlucoseactsasasignaltoyeastcellstoincreasenumberofglucosetransportersandenzymesallowingefficientuptakeanduseofglucoseSignal-TransductionEmphasisThischapter’semphasisisonsignalsthatarereleasedfromonecellandallowedtofreelydiffusetoasecond(ormore)recipientcell(s)Thesecommunicationsaredeliberatelyinitiated,received,andinterpretedinordertoincreasethephysiologicalcoordinationofthecellsinmulticellularorganismsWewillconsiderinparticularthoseeventsthatfollowthereceptionofchemicalsignalsThreeStagesofSignalTransduction1.Receptionofextracellularsignalbycell2.Transductionofsignalfromoutsideofcelltoinsideofcell—oftenmulti-steppedNotenotnecessarilytransductionofligand3.CellularResponseResponseisinititiatedand/oroccursentirelywithinreceivingcellThreeStagesofSignalTransductionThreeStages2a.Transduction2b.Transduction2c.Transduction2d.Transduction1.Reception3.ResponseResponsesusuallyinvolveincreasingordecreasingsomeProtein’sFunctionThreeStages2a.Transduction2b.Transduction1.Reception3.Response物理信号：光、热、电流化学信号：最广泛的信号是化学信号。短肽、蛋白质、气体分子（NO、CO）以及氨基酸、核苷酸、脂类和胆固醇衍生物等。信号分子的共同特点：①特异性，只能与特定的受体结合；②高效性，几个分子即可发生明显的生物学效应，这一特性有赖于细胞的信号逐级放大系统；③可被灭活，完成信息传递后可被降解或修饰而失去活性，保证信息传递的完整性和细胞免于疲劳。信号分子与靶细胞一、信号分子与信号细胞信号分子●非营养物●非能源物质●非结构物质●不是酶◆主要是用来在细胞间和细胞内传递信息①根据细胞受体蛋白组检测可用的特定信号组(数百种信号分子)②细胞按细胞内的装置对接收的信息在细胞内进行不同的整合和译解二、靶细胞信号分子作用的效应细胞专一识别信号反应差异细胞按发育编程，在不同的分化阶段，分别与不同的专一性信号分子结合靶细胞中的受体受体概念:能够识别和选择结合信号分子并能引起一系列生物学效应的生物大分子.◆多为糖蛋白反应特征刺激骨骼肌收缩却降低心肌收缩频率和收缩力引起分泌细胞的细胞分泌乙酰胆碱信号分子可直接穿越质膜脂双层进入靶细胞内部，与细胞内受体结合，激活受体，同专一DNA序列结合，调控基因表达！！！1、胞内受体:于细胞质溶质或核中在30min内直接诱导少数专一基因转录初级反应的转录产物又激活其它基因激活基因转录初级反应(primaryresponse)次级反应(secondaryresponse)表面受体蛋白：胞内受体：受体一些疏水性信号小分子的受体亲水性信号分子的受体2、表面受体同信号配体结合后，将细胞外信号转变成细胞内信号