Chapter-6-Microbial-Nutrition-and-Metabolism--微生物学

Chapter6MicrobialNutritionandMetabolism6.1Nutrientrequirements6.2Nutritionaltypesofmicroorganisms6.3Uptakeofnutrientsbythecell6.3CultureMedia6.4AnOverviewofMetabolism6.5Fermentation:TheEmbden-MeyerhofPathway6.6RespirationandElectronTransport6.7TheBalanceSheetofAerobicRespirationandEnergyStorage6.8AnOverviewofAlternateModesofEnergyGeneration6.9BiosynthesisofMonomers6.10NitrogenfixationChapteroutlineConceptsMicroorganismsrequireabout10elementsinlargequantities,inpartbecausetheyareusedtoconstructcarbohydrates,lipids,proteins,andnucleicacids.Severalotherelementsareneededinverysmallamountandarepartsofenzymesandcofactors.Allmicroorganismscanbeplacedinoneofafewnutritionalcategoriesonthebasesoftheirrequirementsforcarbon,energyandhydrogenatomsorelectrons.Nutrientmoleculesfrequentlycannotcrossselectivelypermeableplasmamembranesthroughpassivediffusion.Theymustbetransportedbyoneofthreemajormechanismsinvolvingtheuseofmembranecarrierproteins.TraceElementsMicrobesrequireverysmallamountsofothermineralelements,suchasiron,copper,molybdenum,andzinc;thesearereferredtoastraceelements.Mostareessentialforactivityofcertainenzymes,usuallyascofactors.GrowthFactorsAminoacidsforproteinsynthesisPurinesandpyrimidinesfornucleicacidsynthesis.Vitaminsaresmallorganicmoleculesthatusuallymakeupallorpartenzymecofactors,andonlyverysmallamountsarerequiredforgrowth.(1)Aminoacids(2)Purinesandpyrimidines,(3)VitaminsMajornutritionaltypeSourcesofenergy,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,protozoa6.2NutritionaltypesofmicroorganismsAlgae,CyanobacteriaCO2+H2OLight+Chlorophyll（CH2O）+O2PurpleandgreenbacteriaCO2+2H2SLight+bacteriochlorophyll（CH2O）+H2O+2SPurplenonsulfurbacteria(Rhodospirillum)CO2+2CH3CHOHCH3Light+bacteriochlorophyll（CH2O）+H2O+2CH3COCH3PhotoautotrophPhotoheterotrophPropertyCyanobacteriaGreenandpurplebacteriaPurplenonsulfurbacteriaPhoto-pigmentChlorophyllBcteriochlorophyllBcteriochlorophyllO2productionYesNoNoElectrondonorsH2OH2,H2S,SH2,H2S,SCarbonsourceCO2CO2Organic/CO2PrimaryproductsofenergyconversionATP+NADPHATPATPPropertiesofmicrobialphotosyntheticsystemsChemoautotrophNitrifyingbacteria2NH4++3O22NO2-+2H2O+4H++132KcalBacteriaElectrondonorElectronacceptorProductsAlcaligensandPseudomonassp.H2O2H2ONitrobacterNO2-O2NO3-,H2ONitrosomonasNH4+O2NO2-,H2ODesulfovibrioH2SO42-H2O.H2SThiobacillusdenitrificansS0.H2SNO3-SO42-,N2ThiobacillusferrooxidansFe2+O2Fe3+,H2ONutrientmoleculesfrequentlycannotcrossselectivelypermeableplasmamembranesthroughpassivediffusionandmustbetransportedbyoneofthreemajormechanismsinvolvingtheuseofmembranecarrierproteins.6.3Uptakeofnutrients1.Phagocytosis–Protozoa2.Permeabilityabsorption–Mostmicroorganisms•Passivetransportsimplediffusion•Facilitateddiffusion•Activetransport•GrouptranslocationPassivediffusionistheprocessinwhichmoleculesmovefromaregionofhigherconcentrationtooneoflowerconcentrationasaresultofrandomthermalagitation.Afewsubstances,suchasglycerol,cancrosstheplasmamembranebypassivediffusion.PassivediffusionTherateofdiffusionacrossselectivelypermeablemembranesisgreatlyincreasedbytheuseofcarrierproteins,sometimescalledpermeases,whichareembeddedintheplasinamembrane.Sincethediffusionprocessisaidedbyacarrier,itiscalledfacilitateddiffusion.TherateoffacilitateddiffusionincreaseswiththeconcentratiotigradientmuchmorerapidlyandatlowerconcentrationsofthediffusingmoleculethanthatofpassivediffusionFacilitateddiffusionThemembranecarriercanchangeconformationafterbindinganexternalmoleculeandsubsequentlyreleasethemoleculeonthecellinterior.Itthenreturnstotheoutwardorientedpositionandisreadytobindanothersolutemolecule.AmodeloffacilitateddiffusionBecausethereisnoenergyinput,moleculeswillcontinuetoenteronlyaslongastheirconcentrationisgreaterontheoutside.T4007.gifActivetransportisthetransportofsolutemoleculestohigherconcentrations,oragainstaconcentrationgradient,withtheuseofmetabolicenergyinput.ActivetransportT4008.gifGrouptranslocationThebest-knowngrouptranslocationsystemisthephosphoenolpyruvate:sugarphosphotransferasesystem(PTS),whichtransportsavarietyofsugarsintoprocaryoticcellswhileSimultaneouslyphosphorylatingthemusingphosphoenolpyruvate(PEP)asthephosphatedonor.GrouptranslocationPEP+sugar(outside)pyruvate+sugar-P(inside)Thephosphoenolpyruvate:sugarphosphotransferasesystemofE.coli.Thefollowingcomponentsareinvolvedinthesystem:phosphoenolpyruvate,PEP;enzyme1,EI;thelowmolecularweightheat-stableprotein,HPr;enzyme11,EII,-andenzymeIII,EIII.ItemsPassivediffusionFacilitateddiffusionActivetransport