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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
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