第六章微生物的營養(yǎng)、生態(tài)和生長

AMicrobiologyCoursebyBoCHEN(e-mail:qqchen36@)第6章微生物的營養(yǎng)、生態(tài)和生長

MicrobialNutrition,Ecology,andGrowthContents6.1MicrobialNutrition6.2EnvironmentalFactorsThatInfluenceMicrobialGrowth6.3TheStudyofMicrobialGrowth6.1MicrobialNutritionChemicalcomponentsofmicrobialcellsSixessentialelementsofmicrobialnutritionNutritionalcategoriesofmicrobesTransportmechanismsfornutrientuptakeWhatisnutrition?Ntritionisaprocessbywhichchemicalsubstancescallednutrientsareacquiredfromtheenvironmentandusedincellularactivitiessuchasmetabolismandgrowth.營養(yǎng)：是指生物為了細(xì)胞活動(dòng)(代謝、生長等)的需要，從環(huán)境中獲取化學(xué)物質(zhì)(營養(yǎng)物)的過程。6.1.1Chemicalcomponentsofmicrobialcells注意：RNA的比例，為何占如此之大的比例？原核細(xì)胞translation;regulation6.1.2Sixessentialelementsofmicrobialnutrition(六大要素)CarbonsourceNitrogensourceEnergysourceGrowthfactorsMineralsaltsWater1.Carbonsource(碳源)Carbonsource:nutrientsprovidingcarbonelement速效，緩效根據(jù)碳源利用能力不同，微生物分為2大類型：自養(yǎng)型微生物和異養(yǎng)型微生物Autotroph(自養(yǎng)型微生物)—

可以利用CO2作為唯一碳源的微生物，可以將CO2轉(zhuǎn)變?yōu)橛袡C(jī)化合物，在營養(yǎng)上不依賴其它生物(無機(jī)營養(yǎng)型)e.g.

光能：藍(lán)細(xì)菌、微藻；化能：氫細(xì)菌、硫桿菌、甲烷桿菌。cf.

植物Heterotroph(異養(yǎng)型微生物)—必須利用有機(jī)物為碳源的微生物，因此在營養(yǎng)上必須依賴其它生物(有機(jī)營養(yǎng)型)e.g.

光能：紅螺細(xì)菌；化能：大多數(shù)細(xì)菌、全部真菌、原生動(dòng)物cf.

動(dòng)物2.Nitrogensource(氮源)Nitrogensource:nutrientsprovidingnitrogenelement速效，緩效3.Energysource(能源)根據(jù)能源利用能力，微生物分為2大類能源類型：化能營養(yǎng)型：利用化學(xué)物質(zhì)的氧化獲得能量光能營養(yǎng)型：利用光獲得能量4.Growthfactors(生長因子)是一類調(diào)節(jié)微生物正常代謝所必需的、需求量很少的、但不能自身合成的有機(jī)物。廣義：包括維生素、氨基酸、堿基等狹義：維生素培養(yǎng)基：酵母膏(yeastextract)、玉米漿(cornsteepliquor)、麥芽汁(maltextract)、肝浸液(liverinfusion)5.Mineralsalts(無機(jī)鹽,礦質(zhì)元素)培養(yǎng)基(culturemedium)：

大量元素(macroelements)：只需加入相應(yīng)化學(xué)試劑即可

微量元素(microelements,traceelements)：一般不必加入(雜質(zhì)中含量即可)6.Water細(xì)胞代謝的場所水的活度(Aw,activityofwater)6.1.3Nutritionalcategoriesofmicrobes結(jié)合碳源和能源進(jìn)行分類√√√√營養(yǎng)類型的其它劃分法6.1.4Transportmechanismsfornutrientuptake小分子：往往直接運(yùn)輸大分子：先降解，再運(yùn)輸大分子營養(yǎng)物質(zhì)先降解，再運(yùn)輸Figure7.2onp194微生物營養(yǎng)物質(zhì)的4種主要運(yùn)輸機(jī)制cf.Table7.5onpage195Passivetransport被動(dòng)運(yùn)輸（不需能量ATP）Activetransport主動(dòng)運(yùn)輸（需要能量ATP）改為：載體介導(dǎo)的主動(dòng)運(yùn)輸Carrier-mediatedactivetransportPassiveTransportSimplediffusionFacilitateddiffusionNature(共同點(diǎn))EnergynotneededConcentrationgradientrequired不需要載體需要特異載體異同點(diǎn)Facilitateddiffusion(p199)SpecificproteincarrierConformationalchange促進(jìn)擴(kuò)散需要特異載體簡單擴(kuò)散不需要載體Simplediffusion(p196)詳細(xì)：被動(dòng)運(yùn)輸ActiveTransportCarrier-mediatedactivetransportGrouptranslocationNature(共同點(diǎn))EnergyrequiredCarrierneededAgainstconcentrationgradient營養(yǎng)分子運(yùn)輸前后沒有發(fā)生變化營養(yǎng)分子運(yùn)輸前后發(fā)生了變化異同點(diǎn)改為：載體介導(dǎo)的主動(dòng)運(yùn)輸Carrier-mediatedactivetransportActivetransport(page200).(a)Molecularpumps,transportingvariousions(sodium,iron)andsmallorganicmolecules.(b)GrouptranslocationPermeasesMembraneproteinchannelBycouplingtransportwithsynthesis,thecellconservesenergy營養(yǎng)分子運(yùn)輸前后沒有發(fā)生變化營養(yǎng)分子運(yùn)輸前后發(fā)生了變化載體介導(dǎo)的主動(dòng)運(yùn)輸?shù)木唧w形式之一詳細(xì)：主動(dòng)運(yùn)輸PhosphotransferasesystemForreferenceonly載體介導(dǎo)的主動(dòng)運(yùn)輸Forreferenceonly6.2EnvironmentalFactorsThatInfluenceMicrobialGrowthTemperatureOxygenpHvalueOsmoticpressureBiologicalfactors6.2.1Temperature㈠根據(jù)微生物生長對溫度的需要，微生物生長有三個(gè)基本溫度點(diǎn)，稱為溫度三基點(diǎn)(Threecardinaltemperatures)：最低溫度、最適溫度、最高溫度Minimumtemperature(最低溫度)

thelowesttemperaturethatpermitsamicrobe’scontinuedgrowthandmetabolism.Belowthistemperature,itsactivitiesareinhibited.應(yīng)用（低溫保藏原理）：食品低溫保藏：低溫抑制生長、抑制代謝(抑制酶活)菌種低溫保藏：冷藏(4℃)；凍藏(低溫-20℃、超低溫-80℃、液氮-165℃)Maximumtemperature(最高溫度)

thehighesttemperatureatwhichgrowthandmetabolismcannotproceed.Ifthetemperaturerisesslightlyabovemaximum,growthwillstop.Ifitcontinuestorisebeyondthatpoint,theenzymesandnucleicacidswillbecomepermanentlyinactivatedordenaturated,andthecellwilldie.Thisiswhyheatworkssowellasanagentinmicrobialcontrol.應(yīng)用：利用高溫消毒、滅菌Optimumtemperature(最適溫度)coversasmallrange,betweentheminimumandmaximum,notapoint,whichpromotesthefastestrateofgrowthandmetabolism. 實(shí)踐意義：微生物培養(yǎng)方面：生長最適溫度(一般情況)：細(xì)菌37℃；酵母25℃；霉菌25-30℃生長的最適溫度與產(chǎn)物產(chǎn)生的最適溫度可能不同：如啤酒釀造中酵母培養(yǎng)與酒精產(chǎn)生、成熟階段采用的溫度不一樣㈡根據(jù)最適生長溫度，微生物分為三個(gè)生態(tài)類群(threeecologicalgroups):Ecologicalgroupsbyadaptationtemperature(p201)1.Mesophiles(嗜中溫微生物,嗜溫微生物):mostfallintotherangeof20℃-40℃.兩群：體溫型最適溫度37℃左右，與動(dòng)物體內(nèi)溫度相適應(yīng)；室溫型最適溫度25℃左右，與環(huán)境溫度相適應(yīng)。Ecologicalgroupsbyadaptationtemperature(p201)2.Psychrophiles(嗜低溫微生物,嗜冷微生物):optimumtemperaturebelow15℃,capableofgrowthat0℃,obligatewithrespecttocold,generallycannotgrowabove20℃.Redsnow(figure7.10onpage202)Ecologicalgroupsbyadaptationtemperature(p201)3.Thermophiles(嗜高溫微生物,嗜熱微生物):growoptimallyattemperaturesgreaterthan45℃.Hyperthermophiles(極端嗜熱微生物):growbetween80℃-110℃Samplingarchaea6.2.2Oxygen(aeration)專性好氧微好氧專性厭氧兼性厭氧耐氧性厭氧好氧微生物厭氧微生物半固體培養(yǎng)基穿刺培養(yǎng)p204㈠Aerobes(好氧微生物)Obligateaerobes(專性好氧微生物)Microaerobes(微好氧微生物)㈡Anaerobes(厭氧微生物)Obligateanaerobes(專性厭氧微生物)Facultativeanaerobes(兼性厭氧微生物)Aerotolerantanaerobes(耐氧性厭氧微生物)*Obligate:strict嚴(yán)格Culturingtechniquesforanaerobes(p204)厭氧接種箱厭氧罐厭氧培養(yǎng)法：厭氧罐半固體培養(yǎng)基穿刺培養(yǎng)靜置培養(yǎng)實(shí)踐意義：微生物培養(yǎng)：通氣措施：棉塞、紗布、振蕩培養(yǎng)、發(fā)酵罐通氣系統(tǒng)、CO2培養(yǎng)(厭氧)保藏：菌種液體石蠟密封、菌種真空保藏(安培管)食品保藏(真空包裝)6.2.3pHvalue根據(jù)微生物生長對pH值的要求：最低pH最適pH 細(xì)菌：中性 真菌：偏酸 放線菌：偏堿最高pH應(yīng)用：培養(yǎng)（e.g.猴頭菇培養(yǎng)基調(diào)酸）分離（e.g.乳酸菌分離）6.2.4Osmoticpressure(滲透壓)培養(yǎng)液的鹽濃度嗜鹽菌(古菌)應(yīng)用：鹽漬食品，糖漬食品6.2.5BiologicalfactorsEcologicalassociationsamongmicrobesInterrelationshipsbetweenmicrobesandanimals(humans)1.Ecologicalassociationsamongmicrobes微生物之間的相互關(guān)系：互生：互相有利，獨(dú)立生存，可單獨(dú)生存共生：互相有利，共同生存，形成共同結(jié)構(gòu)寄生：一方靠另一方生存，對另一方有害拮抗：互相有害，形成對抗?fàn)顟B(tài)2.Interrelationshipsbetweenmicrobesandanimals(humans)微生物與動(dòng)物(人)的相互關(guān)系：Normalmicrobialflora(微生物正常菌群)e.g.腸道菌群：E.coli:vitaminK胃瘤菌群：纖微素消化6.3TheStudyofMicrobialGrowthTheBasisofPopulationGrowth-BinaryFissionTheRateofPopulationGrowthThePopulationGrowthCurveTheMethodsofAnalyzingPopulationGrowth6.3.1TheBasisofPopulationGrowth-BinaryFission細(xì)菌生長考慮的是群體生長(populationgrowth)而不是個(gè)體生長細(xì)菌生長的基礎(chǔ)—二分裂繁殖(binaryfission)Stepsinbinaryfissionofarod-shapedbacterium(p208)binaryfission二分裂繁殖6.3.2TheRateofPopulationGrowthGenerationtime(代時(shí)):thetimerequiredforacompletefissioncycle—fromparentcell(親代細(xì)胞)totwonewdaughtercells(子細(xì)胞).Thelengthofgenerationtimeisameasureofthegrowthrateofamicroorganism.Theaveragegenerationtimeis30-60minunderoptimumconditions.e.g.Theshortestbeing5-10min,Samonellaenteritidis.Staphylococcusaureus,causingfood-borneillness,20-30minThelongest,e.g.Mycobacteriumleprae(causeofleprosy麻風(fēng)病),10-30d(inanimals)ThemathematicsofpopulationgrowthCalculationofGenerationTimeNi—initialnumber;Nf—finalnumber;n—generationnumber;Nf＝Ni×2n

代數(shù)：n＝3.322(lgNf－lgNi)Ti—initialtime;Tf—finaltime;t(orG)—generationtime

代時(shí)：t＝(Tf－Ti)/ne.g.p209e.g.假如一個(gè)三明治污染了10個(gè)金葡細(xì)胞，在小車?yán)?小時(shí)后，金葡的數(shù)量是多少？（假設(shè)代時(shí)是20min）計(jì)算： 代數(shù)(n)=4×60/20=12代 Finalnumber(Nf)=10×212=40,960cells！6.3.3ThePopulationGrowthCurveThegrowthcurveinabacterialculture:Atypicalgrowthcurveforapopulationofcellscanbedividedintofourphases(四個(gè)階段)called:lagphase(滯留適應(yīng)期)exponentialphase(對數(shù)生長期)stationaryphase(穩(wěn)定期)deathphase(死亡期)LagPhase(滯留適應(yīng)期)Whenamicrobialpopulationisinoculatedintoafreshmedium,growthusuallydoesnotbeginimmediatelybutonlyafteraperiodoftimecalledthelagphase,whichmaybebrieforextendeddependingonthehistoryofthecultureandgrowthconditions.Thishappensbecauseforgrowthtooccurinaparticularculturemediumthecellsmusthaveacompletecomplementofenzymesforsynthesisoftheessentialmetabolitesnotpresentinthatmedium.ExponentialPhase(對數(shù)生長期)Itisaconsequenceofthefactthateachcelldividestoformtwocells,eachofwhichalsodividestoformtwomorecells,andsoon.Mostunicellularmicroorganismsgrowexponentially,butratesofexponentialgrowthvarygreatly.Ingeneral,prokaryotesgrowfasterthaneukaryoticmicroorganisms.StationaryPhase(穩(wěn)定期)Ifasinglebacteriumcontinuedtogrowexponentiallyfor48h,apopulationwouldproducethatweighedabout4,000timestheweightofEarth!Thisisparticularlyimpressivebecauseasinglebacterialcellweighsonlyaboutone-trillionth(10?l2)ofagram.Anessentialnutrientoftheculturemediumisuseduporsomewasteproductoftheorganismbuildsupinthemediumtoaninhibitorylevelandexponentialgrowthceases,orboth.DeathPhase(死亡期)Ifincubationcontinuesafterapopulationreachesthestationaryphase,thecellsmayremainaliveandcontinuetometabolize,buttheymayalsodie.Ifthelatteroccurs,thepopulationissaidtobeinthedeathphase.Thegrowthcurveinabacterialculture(p210)Atypicalgrowthcurveforapopulationofcellscanbedividedintofourdistinctphasescalled:lagphase(滯留適應(yīng)期)exponentialphase(對數(shù)生長期)stationaryphase(穩(wěn)定期)deathphase(死亡期)實(shí)踐意義：接種：采用對數(shù)期細(xì)胞發(fā)酵：產(chǎn)物產(chǎn)生，穩(wěn)定期6.3.4TheMethodsofAnalyzingPopulationGrowthTotalcellcount(細(xì)胞總數(shù)測定)Turbiditymeasurement(濁度測定)Viableplatecount(平板活菌計(jì)數(shù))1.Totalcellcount(細(xì)胞總數(shù)測定)血球計(jì)數(shù)板IncludinglivinganddeadcellsThenumberofcellsinapopulationcanb