Chapter7

MicrobialGrowthandGrowthcontrol7.1OverviewofCellGrowth7.2PopulationGrowth7.3MeasurementofGrowth7.4ContinuousCulture:TheChemostat7.5EffectofEnvironmentonGrowth7.6GrowthControl7.7ViralControl7.8FungalControl第1頁(yè)7.1OverviewofmicrobialgrowthThebacterialcellisasyntheticmachinethatisabletoduplicateitself.Thesyntheticprocessesofbacterialcellgrowthinvolveasmanyas2023chemicalreactionsofawidevarietyoftypes.Someofthesereactionsinvolveenergytransformations.Otherreactionsinvolvebiosynthesisofsmallmolecules-thebuilding,blocksofmacromolecules-aswellasthevariouscofactorsandcoenzymesneededforenzymaticreactions.

第2頁(yè)BinaryFission

第3頁(yè)6–1.

MicrobialNutritionNutrientrequirementsNutritionaltypesofmicroorganismsUptakeofNutrientsbytheCellCultureMediumIsolationofPureCultures

第4頁(yè)Microorganismsrequireabouttenelementsinlargequantities,becausetheyareusedtoconstructcarbohydrates,lipids,proteins,andnucleicacids.Severalotherelementsareneededinverysmallamountsandarepartsofenzymesandcofactors.Concepts:Nutrientrequirements第5頁(yè)Macronutrients95%ormoreofcelldryweightismadeupofafewmajorelements:carbon,oxygen,hydrogen,nitrogen,sulfur,phosphorus,potassium,calcium,magnesiumandiron.Thefirstsix(C,H,O,N,PandS)arecomponentsofcarbonhadrates,lipids,proteinsandnucleicacids第6頁(yè)TraceElements

Microbesrequireverysmallamountsofothermineralelements,suchasiron,copper,molybdenum,andzinc;thesearereferredtoastraceelements.Mostareessentialforactivityofcertainenzymes,usuallyascofactors.第7頁(yè)GrowthFactors

Aminoacidsareneededforproteinsynthesis,purinesandpyrimidinesfornucleicacidsynthesis.Vitaminsaresmallorganicmoleculesthatusuallymakeupallorpartenzymecofactors,andonlyverysmallamountsarerequiredforgrowth.(1)aminoacids,(2)purinesandpyrimidines,(3)vitamins第8頁(yè)MajornutritionaltypeSourcesofenergy,hydrogen/electrons,andcarbonRepresentativemicroorganismsPhotoautotroph

(Photolithotroph)Lightenergy,inorganichydrogen/electron(H/e-)donor,CO2carbonsourceAlgae,Purpleandgreenbacteria,CyanobacteriaPhotoheterotroph

(Photoorganotroph)Lightenergy,inorganicH/e-donor,OrganiccarbonsourcePurplenonsulfurbacteria,GreensulfurbacteriaChemoautotroph(Chemolithotroph)Chemicalenergysource(inorganic),InorganicH/e-donor,CO2carbonsourceSulfur-oxdizingbacteria,Hydrogenbacteria,NitrifyingbacteriaChemoheterotroph(Chenoorganotroph)

Chemicalenergysource(organic),OrganicH/e-donor,OrganiccarbonsourceMostbacteria,fungi,protozoaNutritionaltypesofmicroorganisms第9頁(yè)Algae,CyanobacteriaCO2+H2O

Light

+Chlorophyll

（CH2O）+O2PurpleandgreenbacteriaCO2+2H2S

Light

+bacteriochlorophyll

（CH2O）+H2O+2SPurplenonsulfurbacteria(Rhodospirillum)CO2+2CH3CHOHCH3Light

+bacteriochlorophyll

（CH2O）+H2O+2CH3COCH3Photoautotroph:Photoheterotroph:第10頁(yè)P(yáng)ropertycyanobacteriaGreenandpurplebacteriaPurplenonsulfurbacteriaPhoto-pigmentChlorophyllBcteriochlorophyllBcteriochlorophyllO2productionYesNoNoElectrondonorsH2OH2,H2S,SH2,H2S,SCarbonsourceCO2CO2Organic/CO2Primaryproductsof

energyconversionATP+NADPHATPATPPropertiesofmicrobialphotosyntheticsystems第11頁(yè)Chemoautotroph:Nitrifyingbacteria2NH4++3O22NO2-+2H2O+4H++132KcalBacteriaElectrondonorElectronacceptorProductsAlcaligensandPseudomonassp.H2O2H2ONitrobacterNO2-O2NO3-,H2ONitrosomonasNH4+O2NO2-,H2ODesulfovibrioH2SO42-H2O.H2SThiobacillusdenitrificansS0.H2SNO3-SO42-,N2ThiobacillusferrooxidansFe2+O2Fe3+,H2O第12頁(yè)areneededtogrowmicroorganismsinthelaboratoryandtocarryoutspecializedprocedureslikemicrobialidentification,waterandfoodanalysis,andtheisolationofparticularmicroorganisms.Awidevarietyofmediaisavailablefortheseandotherpurposes.Culturemedia第13頁(yè)canbeobtainedthroughtheuseofspreadplates,streakplates,orpourplatesandarerequiredforthecarefulstudyofanindividualmicrobialspecies.

Purecultures第14頁(yè)Nutrientmoleculesfrequentlycannotcrossselectivelypermeableplasmamembranesthroughpassivediffusionandmustbetransportedbyoneofthreemajormechanismsinvolvingtheuseofmembranecarrierproteins.Uptakeofnutrients

第15頁(yè)1,Phagocytosis

–

Protozoa2,Permeabilityabsorption–Mostmicroorganismspassivetransport,simplediffusionfacilitateddiffusionactivetransportgrouptranslocation第16頁(yè)Afewsubstances,suchasglycerol,cancrosstheplasmamembranebypassivediffusion.Passivediffusionistheprocessinwhichmoleculesmovefromaregionofhigherconcentrationtooneoflowerconcentrationasaresultofrandomthermalagitation.passivediffusion第17頁(yè)Therateofdiffusionacrossselectivelypermeablemembranesisgreatlyincreasedbytheuseofcarrierproteins,sometimescalledpermeases,whichareembeddedintheplasinamembrane.Sincethediffusionprocessisaidedbyacarrier,itiscalledfacilitateddiffusion.TherateoffacilitateddiffusionincreaseswiththeconcentratiotigradientmuchmorerapidlyandatlowerconcentrationsofthediffusingmoleculethanthatofpassivediffusionFacilitateddiffusion第18頁(yè)Activetransportisthetransportofsolutemoleculestohigherconcentrations,oragainstaconcentrationgradient,withtheuseofmetabolicenergyinput.

Activetransport第19頁(yè)Grouptranslocation第20頁(yè)1,Phagocytosis

–

Protozoa2,Permeabilityabsorption–Mostmicroorganismspassivetransport,simplediffusionfacilitateddiffusionactivetransportgrouptranslocation第21頁(yè)Afewsubstances,suchasglycerol,cancrosstheplasmamembranebypassivediffusion.Passivediffusionistheprocessinwhichmoleculesmovefromaregionofhigherconcentrationtooneoflowerconcentrationasaresultofrandomthermalagitation.passivediffusion第22頁(yè)Therateofdiffusionacrossselectivelypermeablemembranesisgreatlyincreasedbytheuseofcarrierproteins,sometimescalledpermeases,whichareembeddedintheplasinamembrane.Sincethediffusionprocessisaidedbyacarrier,itiscalledfacilitateddiffusion.TherateoffacilitateddiffusionincreaseswiththeconcentrationgradientmuchmorerapidlyandatlowerconcentrationsofthediffusingmoleculethanthatofpassivediffusionFacilitateddiffusion第23頁(yè)Themembranecarriercanchangeconformationafterbindinganexternalmoleculeandsubsequentlyreleasethemoleculeonthecellinterior.Itthenreturnstotheoutwardorientedpositionandisreadytobindanothersolutemolecule.

AmodeloffacilitateddiffusionBecausethereisnoenergyinput,moleculeswillcontinuetoenteronlyaslongastheirconcentrationisgreaterontheoutside.第24頁(yè)Activetransportisthetransportofsolutemoleculestohigherconcentrations,oragainstaconcentrationgradient,withtheuseofmetabolicenergyinput.

Activetransport第25頁(yè)Thebest-knowngrouptranslocationsystemisthephosphoenolpyruvate:

sugarphosphotransferasesystem(PTS),whichtransportsavarietyofsugarsintoprocaryoticcellswhileSimultaneouslyphosphorylatingthemusingphosphoenolpyruvate(PEP)asthephosphatedonor.GrouptranslocationPEP+sugar(outside)pyruvate+sugar-P(inside)第26頁(yè)Thephosphoenolpyruvate:sugarphosphotransferasesystemofE.coli.Thefollowingcomponentsareinvolvedinthesystem:phosphoenolpyruvate,PEP;enzyme1,EI;thelowmolecularweightheat-stableprotein,HPr;enzyme11,EII,-andenzymeIII,EIII.第27頁(yè)ItemsPassivediffusionFacilitateddiffusionActivetransportGrouptranslocationcarrierproteins

NonYesYesYestransportspeedSlowRapidRapidRapidagainstgradientNonNonYesYestransport

moleculesNospecificity

SpecificitySpecificitySpecificitymetabolicenergyNoneedNeedNeedNeedSolutesmoleculesNotchangedChangedChangedChangedSimplecomparisonoftransportsystems第28頁(yè)Modeofactionofantibacterialantibiotics第29頁(yè)Symbiosisofpeptidoglycan第30頁(yè)6–2.

Microbialgrowth

TheGrowthCurveCelllifecycleMeasurementofMicrobialGrowthMeasurementofCellMassGrowthYieldsandtheEffectsofaLimitingNutrientTheContinuousCultureofMicroorganismsTheChemostatTheInfluenceofEnvironmentalFactorsonGrowthOutline第31頁(yè)

Growthisdefinedasanincreaseincellularconstituentsandmayresultinanincreaseinanorganism'ssize,populationnumber,orboth.

Whenmicroorganismsaregrowninaclosedsystem,populationgrowthremainsexponentialforonlyafewgenerationsandthenentersastationaryphaseduetofactorslikenutrientlimitationandwasteaccumulation.Ifapopulationisculturedinanopensystemwithcontinualnutrientadditionandwasteremoval,theexponentialphasecanbemaintainedforlongperiods.Concepts第32頁(yè)3.Awidevarietyoftechniquescanbeusedtostudymicrobialgrowthbyfollowingchangesinthetotalcellnumber,thepopulationofviablemicroorganisms,orthecellmass.4.Wateravailability,pH,temperature,oxygenconcentration,pressure,radiation,andanumberofotherenvironmentalfactorsinfluencemicrobialgrowth.Yetmanymicroorganisms,andparticularlybacteria,havemanagedtoadaptandflourishunderenvironmentalextremesthatwoulddestroymostorganisms.第33頁(yè)Growthmaybegenerallydefinedasasteadyincreaseinallofthechemicalcomponentsofanorganism.GrowthusuallyresultsinanincreaseinthesizeofacellandfrequentlyresultsincelldivisionGrowthdefinition:第34頁(yè)G1

Primarygrowthphaseofthecellduringwhichcellenlargementoccurs,agapphaseseparatingcellgrowthfromreplicationofthegenomeS

phaseinwhichreplicationofthegenomeoccursG2

Phaseinwhichthecellpreparesforseparationofthereplicatedgenomes,thisphaseincludessynthesisofmicrotubulesandcondensationofDNAtoformcoherentchromosomes,agapphaseseparatingchromosomereplicationfrommiosis.M

phasecalledmiosisduringwhichthemicrotubularapparatusisassociatedandsubsequentlyusedtopullapartthesisterchromosomes.CelllifecycleinEukaryoticcells

G1SG2MG1RDEukaryoticcell:Prokaryoticcell:第35頁(yè)第36頁(yè)Mostbacterialcellsreproduceasexuallybybinaryfision,aprocessinwhichacelldividestoproducetwonearlyequal-sizedprogenycells.Binaryfisioninvolvesthreeprocesses:

Increaseincellsize(cellelongation),DNAreplicationCelldivisionBinaryfision第37頁(yè)GrowthcurveofbacteriaLagPhase

ExponentialPhase

StationaryPhaseDeathPhase

第38頁(yè)GrowthcurveofbacteriaLagPhase

ExponentialPhase

StationaryPhaseDeathPhase

第39頁(yè)(a)

Lagphase:cellsbegintosynthesizeinducibleenzymesandusestoredfoodreserves.(b)

Logarithmicgrowthphase:therateofmultiplicationisconstant.(c)

Stationaryphase:deathrateisequaltorateofincrease.(d)Deathphase:cellsbegintodieatamorerapidratethanthatofreproduction.

LagPhaseStationaryPhaseDeathPhaseLogarithmicgrowthphase第40頁(yè)Thetimerequiredforacelltodivide(anditspopulationtodouble)iscalledthegenerationtime.

generationtimeSupposethatabacterialpopulationincreasesfrom103cellsto109cellsin10hours.Calculatethegenerationtime.NumberofcellsTimeNt=Nox2nNo=numberofbacteriaatbeginningoftimeinterval.Nt=numberofbacteriaatendofanyintervaloftime(t).G=generationtimeT=time,usuallyexpressedinminutesn=numberofgenerationG=tlog2/logNt–logNo第41頁(yè)Chemostatusedforcontinuouscultures.Rateofgrowthcanbecontrolledeitherbycontrollingtherateatwhichnewmediumentersthegrowthchamberorbylimitingarequiredgrowthfactorinthemedium.ContinuouscultureofmicroorganismsChemostat第42頁(yè)Bacteriagrowoverarangeoftemperatures;theydonotreproducebelowtheminimumgrowthtemperattirenorabovethemaximumgrowthtemperature.Withinthetemperaturegrowthrangethereisanoptimumgrowthtemperatureatwhichbacterialreproductionisfastest.

Effectoftemperatureonbacterialgrowthrate第43頁(yè)EnzymesexhibitaQ10sothatwithinasuitabletemperaturerangetherateofenzymeactivitydoublesforevery10'Criseintemperature.第44頁(yè)Microorganismsareclassifiedaspsychrophiles,mesophiles.thermophiles,andextremethemophilesbasedontheiroptimalgrowthtemperature.第45頁(yè)Effectofoxygenconcentration–reductionpotentialEffectofoxygenconcentrationonthegrowthofvariousbacteriain

tubesofsolidmedium

第46頁(yè)(a)Obligateaerobes-growthoccursonlyintheshortdistancetowhichtheoxygendiffusesintothemedium.(b)Facultativeanaerobesgrowthisbestnearthesurface,whereoxygenisavailable,butoccursthroughoutthetube.(c)Obligateanaerobes-oxygenistoxic,andthereisnogrowthnearthesurface.(d)Aerotolerantanaerobes-growthoccurs