微生物生态第七章

微生物生态第七章Twoterms:1.Microbialecology:Isnowusedinageneralwaytodescribethepresenceanddistributionofmicrobes.Itisthestudyofthebehaviorandactivitiesofmicrobesintheirnaturalenvironments.2.Environmentalmicrobiology:Incomparison,relatesprimarilytoall-overmicrobialprocessesthatoccurinasoil,waterorfood,asexles.itisnotconcernedwiththeparticularmicroenvironmentwherethemicrobesactuallyarefunctioning,butwiththebroader-scaleeffectsofmicrobialpresenceandactivities.6.1Microbesinnatureecosystem6.1.1MicrobesandmicroenvironmentInamicrobialecosystem,individualcellsgrowtoformpopulations.Metabolicallyrelatedpopulationsconstitutegroupingscalledguilds.

Setsofguildsconductingcomplementaryphysiologicalprocessesinteracttoformmicrobialcommunities.Microbialcommunitiestheninteractswithcommunitiesofmicrobestodefinetheentireecosystem.6.1.2DistributionofmicrobesThedistributionofmicrobesinnatureecosystemdependsontheresources(nutrients)availableandonthegrowthconditions.Temperature,PH,wateravailability,light,oxygenofahabitatdefinethenicheforeachparticularmicrobes.1.Insoilorganismsinsoilsoilisthehabitat(环境)foravarietyoforganisms,includingbacteria,actinomycetes,fungi,protozoa,insects,nematodes（线虫）,wormsandmanyotheranimals.Virusesalsoarepresentinsoils.Thiscomplexbiologicalcommunitycontributestotheformation（形成）,maintenance（维持）,andinsomesituations,thedegradation（降解）anddisappearance（消失）ofsoils.(2)Soilsasanenvironmentformicrobes:Amajorcharacteristicofsoils

theyaretypicallynotwatersaturated（饱和）,makingitpossibleforoxygentopenetrateintothepassagesandporessoilsalsocancontainisolatedregionswhicharewatersaturated,andtheseisolatedregionsbecome“mini”aquatic（水生的）environments.

Themicroenvironmentbacteriatendtobepresentasisolatedmicrocolonies（微菌落）onsurfacesandinpores,whicharecoveredbythinwaterfilms.Filamentous（丝状的）fungiareabletogrowonandbetweentheseaggregated（聚集的）particles,orprotozoamoveinwaterfilmsandgrazeonbacteria,especiallywhentheyarenotprotectedinsoilpores.

proportionofdifferentsoilmicrobesinsoilAerobicbacteria70%Actinomycetes13%Fungi3%Otherorganisms0.02%Anaerobicbacteria14%Microbialnumberandbiomassincultivatedfieldsoil:

microbesNumbers/gBiomass(g/m3)bacteria108160actinomycetes107160molds106200yeasts105algae10432protozoa103382.InwaterAmajorfactorinaquaticenvironmentsisthemovementofmaterials,whethertheybegaseous,solid,orinthedissolvedphase.Themicrobesareabletorespondrapidlytoselecttheirmostsuitableenvironment.(1)Differenttypesofwater①FreshwaterTypesofmicrobialcommunitiesaccordingtothecontentsoforganicsubstancesDistributionofmicrobesinfreshwaterNutrientenrichmentStimulatesthegrowthofplants,algae,andbacteria.Cyanobacteriaandalgaecancontributetomassiveblooms(水华)instronglynutrientenrichmentlakes.②marineenvironmentMicrobesinoceanAlgae(藻类),Bacillus(芽孢杆菌属),Pseudomonas(假单胞菌属),Vibrio(弧菌属)andsoon.Distributionofmicrobesinocean

Euphoticzone（透光区）

Aphoticzone（无光区）

Bathypelagezone（深海区）;

Hadalzone（超深渊海区）

光照区耐压范围中度嗜压范围极端嗜压范围NorthpoleandsouthpolePolaromonas(极地单胞菌属)，Marinobacter(海杆菌属)，Psychroflexus(嗜冷弯曲菌属)，Iceobacter(冰杆菌属)，Polibacter(极杆菌属)，Psychromonasantarcticus(南极嗜冷单胞菌属)Redtide(2)NutrientcyclesinaquaticenvironmentsInthisloopalargeportionoftheorganicmattersynthesizedbythephytoplanktonduringphotosynthesisisreleasedasdissolvedorganicmatter(DOM).ThisDOMisusedbythebacteria,whichbecomepartoftheparticulateorganicmatter(POM)pool.Aportionofthesebacteriaarethenusedasafoodsourcebyprotozoa.Afterdigestionbytheprotozoa,aportionofthenutrientscontainedinthebacteriaandprotozoaismineralizedandloopedbacktothephytoplankton,makingitunavailabletothehighertrophiclevelsoftheecosystem.浮游动物原生动物颗粒性有机物质可溶性有机物质浮游植物上层消费者3.Inair（1）Isairsuitableforthegrowthofmicrobes?Why?（2）Isthereanymicrobesintheair?Wherearetheyfrom?4.MicrobesinextremelyenvironmentThermophilesPsychrophilesAcidophilesAlkalinophileHalophileBarophilesRadiationresistant6.2UsageofmicrobesFoodIndustry6.2.1InfoodindustryOverthelastthousandyears,fermentationhasbeenamajorwayofpreservingfood.Microbialgrowth,eitherofnaturalorinoculatedpopulations,causeschemicaland/ortexturalchangestoformaproductthatcanbestoredforextendedperiods.Thefermentationprocessalsoisusedtocreatenew,pleasingfoodflavorsandodors.Themajorfermentationusedinfoodarethelactic(乳酸),propionic(丙酸),andethanolic(酒精)fermentations.

1.Fermentedmilks（1）mesophilic（中温型）acidproducedthroughmicrobialactivitycausesproteindenaturation.i.e.

Lactobacillusspp.（乳酸杆菌属）andLactococcuslactis（乳酸乳球菌）culturesareusedforaroma（芳香）andacidproduction.Lactococcuslactissubsp.Diacetilactis（乳酸乳球菌双乙酸亚种）convertsmilkcitrate（柠檬酸盐）todiacetyl（双乙酸酰）,whichgivesaspecialbutteryflavortothefinishedproduct.(2)Thermophilic（嗜热型）Animportantexleisyogurtproduction.Yogurtismadeusingaspecialstartercultureinwhichtwomajorbacteriaarepresentina1:1ratio:S.thermophilus（唾液链球菌）andL.bulgaricus（保加利亚乳酸杆菌）.Withtheseorganismsgrowinginconcert,acidisproducedbyStreptococcus,andaromacomponentsareformedbytheLactobacillus.Freshlypreparedyogurtcontains109bacteriapergram.(3)Therapeutic（治疗型）Fermentedmilksmayhavebeneficialtherapeuticeffects.Functions:AcidophilusmilkisproducedbyusingLactobacillusacidophilus（嗜酸乳杆菌）.L.acidophilusmaymodifythemicrobialflora(菌群)inthelowerintestine,thusimprovinggeneralhealth,anditoftenisusedasadietaryadjunct(饮食调节).minimizinglactoseintoleranceloweringserumcholesterol(血清胆固醇)exhibitinganticanceractivityAnotherinterestinggroupusedinmilkfermentationsarethebifidobacteria（双歧杆菌）.

Theyaretypicalresidentsofthehumanintestinaltract,andfermentlactoseandothersugarstoacetic（醋酸）andlacticacids（乳酸）.Functions:helpmaintainthenormalintestinalbalanceimprovinglactosetolerancepossessantitumorigenic(抗肿瘤发生的)activityreduceserumcholesterollevelspromotecalciumabsorptionandthesynthesisofB-complexvitamins.(4)YeastlacticYeast-lacticfermentationsincludekefir(开菲乳),aproductwithanethanolconcentrationofupto2%.Thisprocessisbasedontheuseofkefirgrainsasaninoculum.Thekefirgrainsaredriedmilksolidsthatcontainavarietyofdesiredbacteriaandyeastsforproductionofkefir.Thesearecoagulatedlumpsofcasein(酪蛋白)thatcontainyeasts（酵母菌）,lacticacidbacteria（乳酸菌）,andaceticacidbacteria（乙酸菌）.Kefirgrainsusedtoinoculatemilkforayeast-lacticfermentation.Afterthefermentationiscompleted,thegrainsarerecovered,washed,andusedtoinoculateanotherbatchoffreshmilk.Bars=1cm(5)Moldlactic

Mold-lacticfermentationresultsinauniqueFinnishfermentedmilkcalledviili.ThemilkisplacedinacupandinoculatedwithamixtureofthefungusGeotrichiumcandidum（白地霉）andlacticacidbacteria（乳酸菌）.2.Cheese3.Meatandfish

Besidesthefermentationofdairyproducts,avarietyofmeatproducts,especiallysausage,canbefermented.Pediococcuscerevisiae(啤酒片球菌)andLactobacillusplantarum（植物乳杆菌）aremostofteninvolvedinsausagefermentations.Halophilicbacillusspeciesismostlyusedtofermentfishtoproducefishsauces.4.酒精饮料4.Otherfermentedfoods6.2.2Inindustry1.BiotechnologyBiotechnologyistheuseoflivingorganismsintechnologyandindustry.Prokaryoteshavebeenexploitedformanyyearsinthemanufactureoffoodandotherusefulproducts.AimProduceproductsorintermediatesEquipmentVats(fermenter)Functions:protectfromcontaminationandchangesinPH,temperatureanddissolvedoxygenconcentration.ModernbiotechnologyReliesheavilyondevelopmentsinchemicalengineeringtoregulateandmonitortheprocessesoccurringinthesefermentersandthisregulationmakesthegrowthofbacteriaundertheseconditionssomewhatdifferentfromthatfoundinordinaryshakeflasks.processForlarge-scaleapplications,prokaryotesaregrowninfermentersusingeitherbatch,fed-batchorcontinuous-cultureprocess.Batchfermenter:issterilized,inoculatedandallowedtogrowbeforetheentireculturevolumeisharvested.Fedbatch:followsasimilarregimen,butinsteadonlysomeofthecultureisharvestedaftergrowth,andfreshmediumisaddedtorestarttheprocess.Continuousculture:usesaconstantin-flowofmedimoffsetbytheexitofspentmedium,productandbiomassandisnotusedsomuchintheproductionofproductsforhumanconsumption.Theimportantroleofbiotechnology:Food-processingindustryProvidingbothenzymese.g.invertase（转化酶）forthemanufactureofglucosesyrup（葡萄糖浆）andbiomolecules

e.g.sodiumglutamate（谷氨酸钠）2.genetechnologyandbiotechnologyTheefficientproductionofsomeproteinsandchemicalscanonlybecarriedoutbymutantorrecombinantmicrobes.Genetechnologyprovidesameansofprovidingvirus-free（无病毒）humanproteins,aswellasfortheoverexpression（超量表达）ofusefulenzymesfromextremeophiles（嗜极菌）.3.fermentedfoodProkaryotesareusedinthemanufactureofasurprisingdiversityofprocessedfood,e.g.cheese,yoghurtandsoysauce.Theroleofbacteriaispredominantlytoconvertcarbohydratesandalcoholsintoorganicacids,loweringthePHandincreasingthestoragelifeandpalatability（美味）ofthefood.Startercultures（起子培养物）areusedtoreducetheduration（持续时间）ofthefermentationprocess.4.biocatalysis

Microbesareaconvenientsourceofenzymes.Thesebacterialenzymesmayeitherbeuseddirectly,orheldinimmobilized（固定化的）cellsforeaseofuse.Theuseofprokaryoteenzymescansignificantlyreducethecostandincreasetheyieldofreactionsanorganicchemistwouldfinddifficulttoperform.

Advantages.

Anexleabouttheproductionofacrylamide(丙烯酰胺)showustheadvantagesofbiocatalysis.Acrylonitrileacrylamide(丙烯腈)(丙烯酰胺)Tothechemicalmethod:Thecatalystiscopperandmustberegenerated;At100℃;Theunreactedhighlytoxicacrylonitrilemustalsoberigorouslyseparatedfromtheproduct;Tothebiocatalysis:UseofimmobilizedPseudomonaschlorophisperformingthebiotransformationinabioreactor;Thereactioncanberunat10℃,soheatingcostsarereduced;Thebacterialenzymeresponsibleconvertsover99.9%oftheacrylonitrileintoacrylamide.

6.2.3Somemainproductsofindustrialmicrobes

1.AntibioticsManyantibioticsareproducedbymicrobes,predominantlybyactinomycetesinthegenusstreptomyces（链霉菌属）

andbyfilamentousfungi.(1)Penicillin(青霉素)Producedbypenicilliumchrysogenum（产黄青霉）.(2)Streptomycin(链霉素)Producedbystreptomycesgriseus（灰色链霉菌）.4.AminoacidAminoacidssuchaslysineandglutamicacidareusedinthefoodindustryasnutritionalsupplementsinbreadproductsandasflavor-enhancingcompoundssuchasmonosodiumglutamate(谷氨酸钠).Aminoacidproductionistypicallycarriedoutbymeansofregulatorymutants(突变株),whichhaveareducedabilitytolimitsynthesisofanendproduct.5.OrganicacidsCitric(柠檬酸),acetic(醋酸),lactic(乳酸),fumaric(延胡索酸)andgluconicacids(葡糖酸)aremajorproducts.6.BiopolymersBiopolymersaremicrobiallyproducedpolymersusedtomodifytheflowcharacteristicsofliquidsandtoserveasgellingagents(胶化剂).Theseareemployedinmanyareasofthepharmaceuticalandfoodindustries.Advantages:productionisindependentofclimate;productionfacilitiesalsocanbelocatednearsourcesofinexpensivesubstrates.Including:Dextrans(葡聚糖):bloodexpandersandabsorbents.Erwiniapolysaccharides(欧文氏菌多糖):PaintsPolyesters(聚酯):derivedfromPseudomonasoleovorans(食油假单胞菌),whichareafeedstock(原料)forspecialtyplastics,foodthickener(增稠剂)。7.Biosurfactants(生物表面活性剂)Functions:Emulsification(乳化作用)Increasingdetergency(去垢性)Wetting(湿化)Phasedispersion(阶段分散)Solubilization(增溶)Oilspilldispersion(漏油分散)Enhanceoilrecovery(提高油的回收)1，neutralism(中性关系)2，commensalism(偏利关系)3，synergism(协同关系)4，mutualism(互惠关系)5，competition(竞争关系)6，antagonism(拮抗关系)7，parasitism(寄生关系)8，predation(捕食关系)6.3MicrobialpopulationinteractionsAB6.3.1Neutralism(中性关系)thereisnoanyphysiologicaleffectbetweenthepopulations.

00isaunidirectional（单方向的）relationshipbetweenpopulationsinwhichonepopulationbenefitsandtheotheroneisunaffected.6.3.2Commensalism(偏利关系)1.Features(tothecommensal):Permitsthecommensal(共生物)tofeedonsubstancescapturedoringestedbythehost;Thecommensaloftenobtainsshelterbylivingeitheronorinthehost;Thecommensalisnotdirectlydependentonthehostmetabolicallyandcausesitnoparticularharm.Whenthecommensalisseparatedfromitshostexperimentally,itcansurvivewithoutbeingprovidedsomefactororfactorsofhostorigin.2.DifferentsituationsofCommensalismbetweenmicrobesThewasteproductofonemicrobeisthesubstrateforanotherspecies.

Nitrosomonas(亚硝化单胞菌),andNitrobacter(硝化细菌)andothersimilarbacteria.NitrobacterbenefitsfromitsassociationwithNitrosomonasbecauseitusesnitritetoobtainenergyforgrowth.

Onemicrobialgroupmodifiestheenvironmenttomakeitmoresuitedforanotherorganism.

ThefacultativelyanaerobicE.coli,andtheobligateanaerobessuchasBacteroides(拟杆菌属).TheanaerobesbenefitfromtheirassociationwiththehostandE.coli,butE.coliderivesnoobviousbenefitfromtheanaerobes.6.3.3Synergism(协同关系)Protocooperation(初级合作),indicatesthatbothpopulationsbenefitfromtherelationshipbuttheassociationisnotobligatory（非专性，非义务的）.Bothpopulationsarecapableofsurvivingindependently.Exles:Desulfovibrio（脱硫弧菌属）andChromatium（着色菌属）Nitrogen-fixingmicrobesandacellulolytic(纤维素降解)organismsuchasCellulomonas（纤维单胞菌属菌）.Amarineworm-bacterialprotocooperativeAlvinellapompejane(庞贝蠕虫),a10cmlongworm,bacteriathatgrowaslongthreadsontheworm’ssurface.Thesewaterscontainsulfurcompoundsthatareusedbythebacteriaaselectronacceptorsinthepresenceoffumarate（延胡索酸）andpyruvate（丙酮酸）,andthewormusesthebacteriaasafoodsource.6.3.4Mutualism（互惠关系）Symbiosisisanobligatoryinterrelationshipbetweentwopopulationsthatbenefitsbothofthem.Exles:Flagellatedprotozoa（鞭毛原生动物）liveinthegutoftermites（白蚁）andwoodroaches（木蟑螂）.Rosecoral(玫瑰珊瑚)andzooxanthellae(虫黄藻)Zooxanthellae(green)withinthetipofahydratentacle(水螅触手)ThegreencolorofthisRosecoral(玫瑰珊瑚)isduetotheabundantzooxanthellae(虫黄藻)withinitstissues.6.3.5Antagonism(拮抗关系)Amensalism(偏害共栖),occurswhenonepopulationproducesasubstrateinhibitorytoanotherpopulation.Exles:Theproductionofantibioticsthatcaninhibitorkillasusceptiblemicrobes.Antibioticproductionandinhibitionofgrowthofasusceptiblebacteriumonanagarmedium.Theattinant-fungalmutualisticrelationshipispromotedbyantibiotic-producingbacteriathataremaintainedinthefungalgardensystem.Inthiscaseastreptomycete(链霉菌)producesanantibioticthatcontrolsEscovopsis,apersistent（持久的）parasiticfungusthatcandestroytheant’sfungal6.3.6Parasitismtheparasitepopulationisbenefitedandthehostpopulationisharmed.Properties:Thehostwillbeharminvolvenutrientacquisitionand/orphysicalmaintenanceinoronthehost.Inparasitismthereisadegreeofcoexistenceoftheparasiteinassociationwiththehost.Dependingontheequilibriumbetweenthetwoorganisms,thismayshiftandwhatmighthavebeenastableparasiticrelationshipmaythenbecomeapathogenic(病原性的)onewhichcanbedefinedaspredation（捕食作用）.

isawidespreadphenomenonwherethepredator（捕食者）engulfsorattackstheprey（猎物）.Thepreycanbelargerorsmallerthantheprey,andthisnormalresultsinthedeathoftheprey.Aninterestingarrayofpredatorybacteriaareactiveinnature.Severalofthebestexlesareshowninfigure,includingBdellovibrio(蛭弧菌),Virococcus（吸血球菌）,andDaptobacter（潜入杆菌）.Bdellovibrio(蛭弧菌)penetratesthecellwallandmultipliesbetweenthewallandtheplasmamembrane,aperiplasmicmodeofattack,followedbylysisofthepreyandreleaseofprogeny(子代蛭弧菌).Virococcus（吸血球菌）attachestothesurfaceoftheprey(anepibioticrelationship)andthensecretesenzymestoreleasethecellcontents.Daptobacter（潜入杆菌）penetratesasusceptiblehostandusesthecytoplasmiccontentsasanutrientsource.6.3.8competitionAriseswhendifferentmicrobeswithinapopulationorcommunitytrytoacquirethesameresource,whetherthisisphysicallocationoraparticularlimitingnutrient.Classificationofpopulationinteraction0,Noeffect;+,positiveeffect;-,negativeeffect.EFFECTOFINTERACTIONNAMEOFINTERACTIONPOPULATIONAPOPULATIONBNeutralismCommensalismSynergismMutualismCompetitionAmensalismParasitismPredation00++-0or+++0+++----6.4Microbes-plantsinteractions6.4.1rootnodulebacteriaandlegumes根毛根瘤菌侵入线已侵入的根瘤菌根瘤6.4.2LichensLichensareleafyorencrustinggrowthsthatarewidespreadinnatureandareoftenfoundgrowingonbarerocks,treetrunks,houseroofsandsurfaceofbaresoils.Thelichenplantconsistsofasymbiosisoftwoorganisms,afungusandanalgae.6.4.3mycorrhizaTherhizosphereisthesoilregioninclosecontactwithplantroots.

Withintherhizosphere,theplantrootsexertadirectinfluenceonthesoilbacteria.Thisinfluenceisknownastherhizosphereeffect.Intherhizosphere,microbialpopulationsreachmuchhigherdensitiesintherhizospherethaninthefreesoil.RhizosphereEffect(R/Sratio)(1)removinghydrogensulfide,whichistoxictotheplantroots(2)increasingsolubilizationofmineralnutrientsneededbytheplantforgrowth(3)synthesizingvitamins,aminoacids,auxins,gibberellinsthatstimulateplantgrowth(4)antagonizingpotentialplantpathogensthroughcompetitionandtheproductionofantibiotics

Microbialpopulationsintherhizospheremaybenefittheplantby:6.5biochemicalcycle6.5.1sulfurcycle

Thebiogeochemicalcyclingofsulfurisextremelycomplex,andconnotbeeasilydescribeddiagrammatically.1.InatmosphereExist:SO2,H2S,COS,CS2,CH3SCH3,CH3SSCH3,CH3SH2.InoceanMarinephotosyntheticagae↓Dimethylsulfoniumpropionate(DMSP)(二甲基磺酸丙酸盐)↓Releasedintosolutiononcelldeat