交大微生物课件lecture5-1microbial二分分裂

Lecture5-1MicrobialGrowthCHAPTER6BROCKBIOLOGYOFSchoolofLifeScienceandBiotechnologyShanghaiJiaoTongUniversity ShanghaiJiaoTongBacterialCellCellGrowthandBinaryInmicrobiologygrowth生长isdefinedasanincreaseinthenumberofcells.Bydefinitionwhenonecelldividestoformtwo,onegeneration世代hasoccurred.ShanghaiJiaoTongOneBinaryfissionOneInmostprokaryotes,growthofanindividualcellcontinuesuntilthecelldividesintotwonewcells,aprocesscalledbinaryfission.ShanghaiJiaoTongFtsproteinsandthecelldivisionFtsproteinsfilamentoustemperaturesensitive”)areimportantinthecelldivisionprocessofprokaryotes.纤维状温度敏感蛋白(Fts蛋白)Ftsproteinsareuniversallydistributedamongprokaryotes,includingtheArchaea,andFtsZproteinshavebeenfoundinmitochondria线粒体and sts叶绿体.Fts蛋白广泛存在于原核生FtsZshowsstructuralsimilaritiestotubulin微管,theimportantcelldivisionproteininShanghaiJiaoTongShanghaiJiaoTongInrod-shapedcells,formationofthedivisomebeginswith entofmoleculesofFtsZinaringaroundthecellintheprecisecenterofthecell.细胞的 (divisome),杆菌的 OtherkindsofLocalizationofnewcellwallsynthesisduringcelldivisionIncocci,newcellwallsynthesis(showningreen)islocalizedatonlyoneShanghaiJiaoTongPeptidoglycansynthesisandcelldivision肽聚2000chemicalreactionsinthecellEnergyBiosynthesisofmonomers,coenzymes,cofactorsPolymerizationreactions-synthesisofpolymersfromShanghaiJiaoTongReview:thepeptidoglycanstructure.(Fig.ShanghaiJiaoTongReview:Overallstructureofpeptidoglycanillustratingtherepeatingsugarsandcrossbridges.(Fig4.30)dBactoprenol细菌萜醇isaveryhydrophobicC55alcohol.Bactoprenoltransportspeptidoglycanbuildingblocksacrossthemembranebyrenderingtheprecursorssufficientlyhydrophobictodpassthroughtheinteriorofthe smic.2Transpeptidationthepenicillintarget转肽作用:Thetranspeptidationreactionleadstothefinalcross-linkingoftwopeptidoglycanchains.Penicillininhibitsthisreaction.GrowthofBacterial细菌群体ShanghaiJiaoTongWhat’sthedifferencebetweengrowthofmacroorganismsandmicroorganisms?Growthandreproductioncanbedistinctfor GrowthisincreaseinsizeandreproductionisincreaseinnumberGrowthandreproductionisthesameGrowthisanincreaseinthenumberofcells生ShanghaiJiaoTongShanghaiJiaoTongBacteriaexistasIndividualcellshaveashortlifespan,butPopulationsarethewaybacteriaexistas 细胞生命短暂,群体是细菌作 Inmicrobiology,growth/reproductionisanincreaseinthenumber(ormass)ofcellsShanghaiJiaoTongShanghaiJiaoTongGrowthterminologyandtheconceptofexponentialgrowthGrowth-anincreaseinthenumber(mass)ofmicrobialcellsinapopulationGrowthrate-thechangeincellnumberorcellmassperunittime生长率:单位时间细胞数量的变Generation-theintervalfortheformationoftwocellsfromone世代:一个细胞生成两个细胞的ShanghaiJiaoTongShanghaiJiaoTong Growthofamicroorganismwherethenumberofcellsdoublesduringeachunittimeperiodiscalledexponentialgrowth.对生长阶ShanghaiJiaoTongGrowthrateiseverincreasinginexponentialgrowth对ShanghaiJiaoTongThemathematicsofexponentialGenerationtime代时thetimerequiredforonegenerationtooccurforthecelltodoubleinapopulation一个世代产生所需的时间Inatimeoft,apopulationgrowngenerationstoincreaseitscellnumberfromN0toNN=N0Thegenerationtimeg=t/n=t/3.3(logN-Ifyoucanmeasurethegrowthtime,initialcellnumber,endcellnumber,generationtimecanthenbe

ShanghaiJiaoTongMethodofestimatingthegenerationtimes(g)ofexponentiallygrowingpopulationswithgenerationtimesof(a)6hand(b)2hfromdataplottedonsemilogarithmicgraphs.Theslopeofeachlineisequalto0.301/gandnequalsthenumberofgenerationsthathaveoccurredinthetime,t.Growthrateconstant生长速率常数(specificgrowthThenumberofgenerationsthatoccurperunittimeinanShanghaiJiaoTongWhatwouldhappenifacellgrowexponentiallyforalongtime?StartfromasinglecellGenerationtime20minGrowexponentiallyfor48hrHowmanycellscanwegetintheend?•= XHowmuchdotheyweight?•X1043cellsX10-12gram/cell=X1031X1025That’s4000timestheweightoftheearthShanghaiJiaoTongShanghaiJiaoTongTheGrowthCycle生长周Inanenclosedvessel,referredtoasabatchculture,atypicalgrowthcurveforapopulationofcellscanbedividedintoseveraldistinctphases:批量培养的典型生长曲线可分为以下四个时Lagphase迟滞期Exponentialphase对数期Stationaryphase稳定期Deathphase衰亡期ShanghaiJiaoTongTypicalgrowthcurveofbacterialpopulationsinbatchculture批5.6.1LagPhase迟滞生长timerequiredfor5.6.1LagPhase迟滞生长dependingonthehistoryofinoculumandgrowthThewaytoshortenlagIftheinoculumisinexponentialgrowthphase,growthconditionsarethesame,lagperiodisIftheinoculumhasbeenstoredinfridge,warmittogrowthtemperaturecanshortenthelagphase.5.6.2ExponentialPhaseperiodthatthenumberof5.6.2ExponentialPhaseCellsinmid-exponentialphaseareThincellusedforenzymeresearch,forgenetictransformationandforpurificationofcellcomponents5.6.3StationaryPhasePeriodthatexponentialgrowthstopsandcellnumberremainconstantWhatstopsexponentialEssentialnutrientdepletion(anessentialnutrientisusedup)必需营养成份的消耗Crypticgrowth-deathrateandgrowthrate‘隐性生长 率与生长率相PeriodofDeathphaseisalsoexponential;butinmostcases,therat