醫(yī)學(xué)微生物課件(英文版)

病原生物學(xué)

MedicalMicrobiologyandParasitologyPartI:MedicalMicrobiologyPartII:MedicalParasitologyIntroductionMicroorganisms(Microbes)MicrobiologyMedicalMicrobiologyWhatisMicroorganismsMicroorganismsarecreaturesthatarenotdirectlyvisibletotheunaidedeye,withdramaticalbiologicdiversity.Viruses,bacteria,fungi,protozoaandsomealgaeareallinthiscategoryAllwiththeexceptionofplantsandanimalsDistributionofmicroorganismsAirSoilWaterAnimalsHumanbody100m300m1400m2100m3150m4050m6000mMicroorganismsandHumanBeingsBeneficialactivities:Mostmicrobesareofbenefittohumanbeings,somearenecessary(nitrogen,carboncycles,etc)Harmfulactivities:Aportionofmicrobescausediseasesandarepoisonoustohuman,andthesearereallythatconcernusinthestudyofmedicalmicrobiology,etc.MicrobiologyMicrobiologyisthebiologyofmicroorganisms.Itisabioscienceforthestudyoftheevolution,Classification,morphology,physiology,genetics,ecologyofmicrobesundercertaindefiniteconditions,Thelawoftheirlifeactivities,andtheirinteractionwithhumanbeing,animalsorplantsaswellaswithnaturalenvironment.TheImportanceofMicrobiologyEnvironmentMedicineFoodIndustryBiotechnologyResearchHistoryofMicrobiologyExperiencephase經(jīng)驗時期Experimentalphase實驗時期Modernphase現(xiàn)代微生物學(xué)時期ExperiencephaseExperimentalphaseLeeuwenhoekPasturKochListerKoch’spostulates

Themicrobemustbefoundinthebodyinallcasesofthedisease

ItmustbeisolatedfromacaseandgrowninaseriesofpurecultureinvitroItreproducethediseaseontheinoculationofalatepurecultureintoasusceptibleanimal

Themicrobemustbeisolatedagainintopureculturefromsuchexperimentallycausedinfection.

艾利希，1910ModernphaseFei-FanTangEmergingandReemergingInfectiousDiseaseAIDSTuberculosisHepatitisGastric

ulcerSRASMedicalMicrobiologyThemedicalmicrobiologyisoneoftheessentialbasicsciencesformedine.ItisthestudyofBiologicalcharacteristicsofmicroorganismsandtheirrelationshipswithhumanhosts

MedicalBacteriologyMedicalViriologyMedicalMycologyParasitologyImmunologySIZEOFBACTERIAUnitformeasurement:Micronor

micrometer,μm:1μm=10-3mm

Size:

Varieswithkindsofbacteria,andalsorelatedtotheirageandexternalenvironment.Cocci:sphere,1μmBacilli:rods,0.5-1μminwidth-3μminlengthSpiralbacteria:1~3μminlengthand0.3-0.6μminwidthStructureofBacteria

Particularstructurescapsule莢膜flagella鞭毛pili菌毛spore

芽胞Essentialstructures

cellwall細(xì)胞壁

cellmembrane細(xì)胞膜

Cytoplasm細(xì)胞質(zhì)

nuclearmaterial

核質(zhì)Gram+Gram-CellwallCell(inner)membraneOutermembraneRibosomesGranuleCellwallNucleoidCellmembraneCapsuleFlagellumPiliGram,C.1884.UeberdieisolirteFarbungderSchizomyceteninSchnitt?undTrockenpraparaten.FortschrittederMedicin,Vol.2,pages185-189.

1884:ChristianGram:FirstpublicationfortheGramstainmethod)Editor'snote:IwouldliketotestifythatIhavefoundtheGrammethodtobeoneofthebestandformanycasesthebestmethodwhichIhaveeverusedforstainingSchizomycetes.CellwallSituation:outmostportion.15-30nminthickness,10%-25%ofdryweight.Cellwall:CommonpeptidoglycanlayerAbackboneofN-acetylglucosamineandN-acetylmuramicacid:BothdiscoveredinGrampositiveandGramnegativebacteria.AsetofidenticaltetrapeptidesidechainattachedtoN-acetyl-muramicacid:differentcomponentsandbindingmodesinGrampositiveandGramnegativebacteria.Asetofidenticalpeptidecrossbridges:onlyinGrampositivebacteriaSpecialcomponentsofGrampositivecellwall

Teichoicacid

SPA/MPOTEINSpecialcomponentsofGramnegativecellwall

FunctionsofCellWallMaintainingthecell'scharacteristicshape-therigidwallcompensatesfortheflexibilityofthephospholipidmembraneandkeepsthecellfromassumingasphericalshapeCounteringtheeffectsofosmoticpressureProvidingattachmentsitesforbacteriophagesProvidingarigidplatformforsurfaceappendages-flagella,fimbriae,andpiliallemanatefromthewallandextendbeyonditPlayanessentialroleincelldivisionBethesitesofmajorantigenicdeterminants

ofthecellsurface。ResistanceofAntibiotics

Wall-lessformsofBacteria.Whenbacteriaaretreatedwith1)enzymesthatarelyticforthecellwalle.g.lysozymeor2)antibioticsthatinterferewithbiosynthesisofpeptidoglycan,wall-lessbacteriaareoftenproduced.Usuallythesetreatmentsgeneratenon-viableorganisms.Wall-lessbacteriathatcannotreplicatearereferredtoasspheroplasts(whenanoutermembraneispresent)orprotoplasts(ifanoutermembraneisnotpresent).Occasionallywall-lessbacteriathatcanreplicatearegeneratedbythesetreatments(Lforms).CellmembraneSiteofbiosynthesisofDNA,cellwallpolymersandmembranelipids.

SelectivepermeabilityandtransportofsolutesintocellsElectrontransportandoxidativephosphorylationExcretionofhydrolyticexoenzymesMesosomesMesosomesarespecializedstructuresformedbyconvolutedinveigh-nationsofcytoplasmicmembrane,anddividedintoseptalandlateralmesosome.Cytoplasm

Composedlargelyofwater,togetherwithproteins,nucleicacid,lipidsandsmallamountofsugarsandsaltsRibosomes:numerous,15-20nmindiameterwith70S;distributedthroughoutthecytoplasm;sensitivetostreptomycinanderythromycinsiteofproteinsynthesisPlasmids:extrachromosomalgeneticelementsInclusions:sourcesofstoredenergy,e,gvolutinPlasmidPlasmidsaresmall，circular/line，extrachromosomal，double-strandedDNAmolecules。Theyarecapableofself-replicationandcontaingenesthatconfersomeproperties，suchasantibioticresistance，virulencefactors。Plasmidsarenotessentialforcellularsurvival.

InclusionsofBacteriaInclusionsareaggregatesofvariouscompoundsthatarenormallyinvolvedinstoringenergyreservesorbuildingblocksforthecell.Inclusionsaccumilatewhenacellisgrowninthepresenceofexcessnutrientsandtheyareoftenobservedunderlaboratoryconditions.granuloseNucleus

Lackingnuclearmembrane,absenceofnucleoli,henceknownasnucleicmaterialornucleoid,onetoseveralperbacterium.CapsulesandslimelayersThesearestructuressurroundingtheoutsideofthecellenvelope.Theyusuallyconsistofpolysaccharide;however,incertainbacillitheyarecomposedofapolypeptide(polyglutamicacid).Theyarenotessentialtocellviabilityandsomestrainswithinaspecieswillproduceacapsule,whilstothersdonot.Capsulesareoftenlostduringinvitroculture.AttachmentProtectionfromphagocyticengulfment.Resistancetodrying.Depotforwasteproducts.Reservoirforcertainnutrients.

protectionFlagella

Monotrichate/Amphitrichate/Lophotrichate/Peritrichate

IdentificationofBacteriaPathogenesisMotilityofbacteriaSomebacterialspeciesaremobileandpossesslocomotoryorganelles-flagella.FlagellaconsistofanumberofproteinsincludingflagellinThediameterofaflagellumisthin,20nm,andlongwithsomehavingalength10timesthediameterofcell.Duetotheirsmalldiameter,flagellacannotbeseeninthelightmicroscopeunlessaspecialstainisapplied.Bacteriacanhaveoneormoreflagellaarrangedinclumpsorspreadalloverthecell.PiliPiliarehair-likeprojectionsofthecell,Theyareknowntobereceptorsforcertainbacterialviruses.ChemicalnatureispilinClassificationandFunctionCommonpiliorfimbriae:fine,rigidnumerous,relatedtobacterialadhesionSexpili:longerandcoarser,only1-4,relatedtobacterialconjugationEndospores(spores)DormantcellResistanttoadverseconditions -hightemperatures -organicsolventsProducedwhenstarvedContaincalciumdipicolinateDPA,DipicolinicacidBacillusandClostridiumIdentificationofBacteriaPathogenesisResistanceBacterialchemicalcomponents

Water:freewaterandcompoundwater.

Inorganicsalt:phosphus,potassiummagnesium,calcium,nitrium,etc.

Protein:50%-80%ofdryweightaccordingbacterialkindsandage.

Sugar:mainlydistributingincellwallandcapsule.

Lipids:composedoflipid,fattyacid,wax,etc.

Nucleicacid:RNAandDNA.

Environmentalfactorsaffectinggrowthofbacteria

1.Nutrients

2.Temperature

3.hydrogenionconcentration(pH)

4.OxygenRequirements:氧氣、二氧化碳5.Osmoticpressure滲透壓

BacterialNutritionandGrowthClassificationbasedontheirsourceofcarbon

根據(jù)細(xì)菌所利用的能源和碳源的不同，將細(xì)菌分為兩大營養(yǎng)類型。1.Autotrophs自養(yǎng)菌

2.Heterotrophs異養(yǎng)菌:saprophytes腐生菌;parasites寄生菌

Nutrientrequirementsofbacterialgrowth:

1.Water2.Carbonsource3.Nitrogensource氮源

4.Minerals無機鹽5.Growthfactors生長因子：thatacellmusthaveforgrowthbutcannotsynthesizeitself.Suchasaminoacids,purines嘌呤,pyrimidines嘧啶,andvitamins

流感嗜血桿菌X因子（高鐵血紅素）

V因子（輔酶Ⅰ或Ⅱ）

TemperaturePsychrophilicforms嗜冷菌

(15-20℃)

Mesophilicforms嗜溫菌（30-37℃）includeallhumanpathogensandopportunists.

Thermophilicforms嗜熱菌（50-60℃）

pHNeutrophiles嗜中性菌（5to8）

Acidophiles嗜酸性菌（below5.5）Alkaliphiles嗜堿性菌（above8.5）GasRequirements

Obligateanaerobes專性厭氧菌

缺乏分解有毒氧基團的酶：catalase觸酶,peroxidase過氧化物酶,superoxidedismutase超氧化物歧化酶

缺乏氧化還原電勢高的呼吸酶：細(xì)胞色素、細(xì)胞色素氧化酶破傷風(fēng)梭菌、肉毒梭菌2O2-+

2H+SODH2O2+O2

2H2O2觸酶2H2O+O2H2O2+AH2

過氧化物酶2H2O+ACO2N.meningitidisN.gonorrhoeae

BacterialGrowth

Bacteriamultiplybybinaryfission二分裂

Generationtime代時：

thetimeittakesforapopulationofbacteriatodoubleinnumbermanycommonbacteria：20~60minmostcommonpathogensinthebody：5-10hoursPopulationdynamics群體動力學(xué)--thegrowthcurve生長曲線

a.TheLagPhase遲緩期(A)

b.TheExponentialPhase指數(shù)期(C)

c.TheMaximumStationaryPhase穩(wěn)定期(E)

d.TheDeathordeclinePhase衰亡期(F)

對數(shù)期遲緩期growthcurve

0515202530105.56.08.58.07.57.06.59.0衰退期總菌數(shù)活菌數(shù)細(xì)菌數(shù)的對數(shù)次小時穩(wěn)定期MicrobialMetabolism

細(xì)菌的新陳代謝EnergyMetabolismMedicalImportantMetabolicProductsanabolicprocesses合成代謝

catabolicprocesses分解代謝

EnergyMetabolism1.CellularrespirationistheprocesscellsusetoconverttheenergyinthechemicalbondsofnutrientstoATPenergy.細(xì)胞呼吸是細(xì)胞將營養(yǎng)物質(zhì)化學(xué)鍵中的能量轉(zhuǎn)化為ATP的過程。

Aerobicrespiration需氧呼吸

Anaerobicrespiration無氧呼吸

2.Fermentation發(fā)酵

MetabolicProductsandBiochemicalTesting代謝產(chǎn)物和生化試驗a.CarbohydrateFermentationTests糖發(fā)酵試驗b.MethylRed(MR)Test甲基紅試驗葡萄糖→丙酮酸→乙酰甲基甲醇甲基紅-葡萄糖→丙酮酸甲基紅+大腸桿菌＋產(chǎn)氣桿菌－c.Voges-Proskauer(VP)Test

葡萄糖→丙酮酸→乙酰甲基甲醇→二乙酰→紅色化合物+胍基化合物葡萄糖→丙酮酸

－大腸桿菌－產(chǎn)氣桿菌＋d.CitrateUtilizationTest枸櫞酸鹽利用試驗

利用枸櫞酸鹽生長+不能利用-大腸桿菌－產(chǎn)氣桿菌＋e.IndoleTest吲哚試驗

色氨酸→吲哚→玫瑰吲哚

吲哚試劑大腸桿菌＋產(chǎn)氣桿菌－IMViC試驗VPtestCitrateutilizationtestIndoltestMethyltest

I

M

Vi

C大腸桿菌++——產(chǎn)氣桿菌——++常用于腸道桿菌的鑒定f.Hydrogen

Sulfide(H2S

)Production硫化氫試驗g.UreaseTest尿素酶試驗

SyntheticProducts

a.Pyrogen熱原質(zhì)（致熱原）Thisisafever-producingsubstancesynthesizedbybacteria.細(xì)菌合成的一種注入人體或動物體內(nèi)能引起發(fā)熱反應(yīng)的物質(zhì)。LPS/耐高溫/去除方法：250℃干烤、蒸餾、吸附劑等/制備和使用注射藥品過程無菌操作

b.ToxinsandInvasiveEnzyme

毒素與侵襲性酶

ExotoxinInvasiveEnzyme（侵襲性酶）c.Pigments色素

水溶性（綠膿桿菌）脂溶性（金黃色葡萄球菌）d.Antibiotics抗生素e.Bactericin細(xì)菌素

f.Vitamins維生素

ArtificialCultivationofBacteria

細(xì)菌的人工培養(yǎng)

Medium培養(yǎng)基：由人工方法配制而成的，專供微生物生長繁殖使用的混合營養(yǎng)物制品Classificationaccordingtobasicingredients

a.Minimalessentialgrowthmedium基礎(chǔ)培養(yǎng)基b.Enrichmentmedium

增菌培養(yǎng)基

c.Selectivemedium選擇培養(yǎng)基

d.Differentialmedium鑒別培養(yǎng)基Classificationaccordingtophysicalcondition:

a．liquidmedium

b．solidmedium

C．semisolidmedium

Phenomenaofbacterialgrowth

Inliquidmedium

表面生長

沉淀生長

混濁生長

Onplate

Semisolidmedium

無動力有動力Purposesofbacterialartificialcultivation

感染性疾病的診斷，鑒別和藥敏試驗生物制品的制備細(xì)菌學(xué)研究designatedbyaLatinbinominal（拉丁雙名法）

前屬名，后種名Staphylococcus(genus)aureus(species)

BacterialClassification科有共同血緣關(guān)系的屬組成科鏈球菌科屬性狀相近關(guān)系密切的若干種組成一個菌屬鏈球菌屬種分類的基本單位，生物學(xué)基本相同的成一個種肺炎鏈球菌型種內(nèi)的細(xì)菌根據(jù)某些差異進一步分型或亞種肺炎鏈球菌3型株對不同來源的同一種的細(xì)菌稱青霉素耐藥株界、門、綱、目、科、屬、種

SomeofthefeaturesthathavebeenusedtoclassifybacteriaGramstain(cellwallstructure)

MolepercentG+Cinthegenome

Growthtemperature

Abilitytoformheatstablespores

Electronacceptorsforrespiration(ifany)

Photosyntheticability

Motility

Cellshape

Abilitytousevariouscarbonandnitrogensources

Specialnutritionalrequirements(e.g.,vitamins)Basictermssterilization滅菌disinfection消毒Antisepsis防腐Bacteriostasis抑菌Asepsis無菌

sterilization滅菌Theprocessofdestroyingallmicrobialforms.Asterileobjectisonefreeofallmicrobialforms,includingbacterialspores.disinfection消毒Thereductionoreliminationofpathogenicmicroorganismsinoronmaterials,sotheyarenolongerahealthhazard.Antisepsis防腐Useofchemicalagentsonskinorotherlivingtissuetoinhibitoreliminatemicrobes;nosporicidal(殺芽胞的)actionisimplied.Bacteriostasis抑菌

Inhibitsthegrowthofmicroorganisms.Asepsis無菌

Nolivingmicroorganismsexists.ControllingMicroorganismsByPhysicalAgentsHighTemperature

Radiation輻射Filtration過濾LowTemperatureDesiccation干燥HighTemperature

staticactioncidalactionDryheat干熱：proteinoxidation

Hotairsterilization干烤

Incineration焚化redheat赤熱flaming燒灼

Moistheat濕熱：denatureproteinsandmeltlipids;moreeffective

Autoclaving:121℃,103.4kPa,

20min

cidalforbothvegetativeorganismsandendosporesBoilingwater煮沸滅菌

Pasteurization巴氏消毒法:tokillparticularspoilageorganismsorpathogensflashmethod瞬間法:71.6°C,15sholdingmethod持續(xù)法:62.9°C,30minfractionalsterilization間歇蒸氣滅菌法

:1)Steamheatingto100°Cfor30min——常壓/流動蒸氣消毒法

Vegetativecellsaredestroyedbutendosporessurvive

2)Incubateat30°C-37°Covernight

Mostbacterialendosporesgerminate

3)Secondheattreatment,100°C,30min

Germinatedendosporesarekilled.

4)Secondincubationat30°C-37°Covernight

Remainingendosporesgerminate

5)Thirdheattreatment,100°C,60min

Lastremaininggerminatedendosporesarekilled

Radiation

UltravioletRadiation紫外線輻射

IonizingRadiation電離輻射

UltravioletRadiationmicrobicidalactivityofultraviolet(UV)lightdependson:lengthofexposure

wavelengthofUV:260nm-270nm

Mechanism:thymine-thyminedimmers胸腺嘧啶二聚體

photoreactivation光復(fù)活作用strongvisiblelight

verypoorpenetratingpower

damagetheeyes,causeburns,andcausemutationincellsoftheskin

IonizingRadiation電離輻射

X-raysandgammarays

moreenergyandpenetratingpowerthanUVusedtosterilizepharmaceuticalsanddisposablemedicalsuppliessuchassyringes,surgicalgloves,catheters導(dǎo)尿管,andsutures縫合線usedtoretardspoilageinseafoods,meats,poultry,andfruits

Filtration過濾

sterilize

solutionsthatmaybedamagedordenaturedbyhightemperaturesorchemicalagents

LowTemperature

inhibitsmicrobialgrowthbyslowingdownmicrobialmetabolism

Desiccation干燥hasastaticeffectonmicroorganismsby

inhibitingtheactionofmicrobialenzymes

UsingDisinfectantsandAntisepticstoControlMicroorganisms

Antimicrobialmodesofactionfordisinfectantsandantiseptics

damagethelipidsand/orproteinsofthesemipermeablecytoplasmicmembraneofmicroorganismsresultinginleakageofcellularmaterialsneededtosustainlifedenaturemicrobialenzymesandotherproteinsbydisruptingthehydrogenanddisulfidebonds

Differentcategoriesofsuchchemicalagents

Phenolandphenolderivatives

altermembranepermeabilityanddenatureproteinschlorhexidine洗必泰

ineffectiveagainstendospores

SoapsanddetergentsAnionic(negativelycharged)detergents:mechanicallyremovemicroorganismsandothermaterialsbutarenotverymicrobicidal.Cationic(positivelycharged)detergents:altermembranepermeabilityanddenatureproteins;ineffectiveagainstendospores,M.tuberculosis結(jié)核分枝桿菌,andP.species假單胞菌.

Alcohols

denaturemembranes70%solutionsofethylorisopropylalcohol乙醇或異丙醇ineffectiveagainstendosporesandnon-envelopedviruses

AcidsandalkaliesaltermembranepermeabilityanddenatureproteinsandothermoleculesSaltsoforganicacids:foodpreservativesUndecylenicacid十一烯酸:dermatophyte皮膚真菌infections

HeavymetalsdenatureproteinsMercurycompounds(mercurochrome紅汞,merthiolate硫柳汞):bacteriostatic,ineffectiveagainstendosporesSilvernitrate硝酸銀(1%):putintheeyesofnewbornstopreventgonococcalophthalmia淋菌性眼炎

Chlorine

reactswithwatertoformhypochlorite次氯酸鹽

ions,whichinturndenaturemicrobialenzymes

Iodineandiodophoresdenaturesmicrobialproteinseffectiveagainstsomeendospores

Aldehydes醛denaturemicrobialproteinsFormalin福爾馬林(37%aqueoussolutionofformaldehydegas)glutaraldehyde戊二醛:killvegetativebacteriain10-30minutesandendosporesinabout4hoursFactorsInfluencingAntimicrobialActivity

Theconcentrationandkindofachemicalagentused;Theintensityandnatureofaphysicalagentused;Thelengthofexposuretotheagent;Thetemperatureatwhichtheagentisused;Thenumberofmicroorganismspresent;Thespeciesorstrainofmicroorganism;Thenatureofthematerialbearingthemicroorganism;Thepresenceoforganicorotherinterferingsubstances.

常用的化學(xué)消毒劑類別作用機制常用種類酚類蛋白變性，細(xì)胞膜損傷洗必泰醇類去除脂類，蛋白變性乙醇鹵素蛋白變性氯氣、碘酊、碘伏重金屬鹽蛋白變性紅汞、硫柳汞、硝酸銀醛類蛋白變性福爾馬林、戊二醛表面活性劑蛋白變性，細(xì)胞膜損傷新潔而滅酸堿類染料破壞細(xì)胞膜、細(xì)胞壁，蛋白變性干擾氧化、抑制繁殖十一烯酸龍膽紫1.殺滅芽胞最常用和最有效的方法是：____________。a.紫外線照射b.煮沸5minc.巴氏消毒法d.流通蒸氣滅菌法e.高壓蒸氣滅菌法2.滅菌方法錯誤的是____________。a.手術(shù)室空氣-紫外線b.排泄物-漂白粉c.飲水-氯氣d.含血清培養(yǎng)基-高壓蒸氣滅菌e.溫度計-75%酒精3.下述不可能殺滅細(xì)菌芽胞的方法是：____________。a.煮沸法b.巴氏消毒法c.間歇滅菌法d.干熱滅菌法e.高壓蒸氣滅菌法4.關(guān)于紫外線，說法錯誤的是____________。(第03章)a.其殺菌作用與波長有關(guān)b.可損壞細(xì)菌的DNA構(gòu)型c.260-270nm殺菌作用最強d.其穿透力弱，故對人體無損害e.紫外線適用空氣和物體表面的消毒5.____________常用于空氣或物體表面的消毒。(第03章)a.高壓蒸氣滅菌法b.紫外線照射法c.濾過除菌法d.巴氏消毒法e.干烤法

6.____________常用于基礎(chǔ)培養(yǎng)基滅菌。(第03章)a.高壓蒸氣滅菌法b.紫外線照射法c.濾過除菌法d.巴氏消毒法e.干烤法Bacteriophages(phages)areobligateintracellularparasitesthatmultiplyinsidebacteriabymakinguseofsomeorallofthehostbiosyntheticmachinery.Theyarevirusesthatinfectbacteria.CompositionofBacteriophageNucleicacid:eitherDNAorRNAbutnotbothdsDNA,

ssRNA,

ssDNA

unusualormodifiedbasesencode3-5geneproductstoover100geneproducts

Protein:functionininfectionandprotectthenucleicacid

StructureofBacteriophage

differentsizesandshapes

icosahedral二十面體

filamentousTailTailFibersBasePlateHeadContractileSheathCapsidDNATypesofBacteriophageLyticorVirulentPhages

毒性噬菌體

LysogenicorTemperatePhage

溶原性噬菌體或溫和噬菌體

LyticorVirulentPhagesDefinition:

Lyticorvirulentphagesarephageswhichcanonlymultiplyinbacteriaandkillthecellbylysisattheendofthelifecycle.

LifeCycleAdsorption吸附

Penetration穿入

BiologicalSynthesis生物合成

MaturationandRelease成熟和釋放

Adsorption吸附Penetration穿入

BiologicalSynthesis生物合成

MaturationandRelease成熟和釋放

BacteriophagebindingtoandinjectingtheirDNAintoabacterialcellnormalbacteriophage

bacteriophageaftercontractionofsheath

AssayforLyticPhage

Plaqueassay噬斑測定

Lyticphageareenumeratedbyaplaqueassay.Aplaqueisaclearareawhichresultsfromthelysisofbacteria.Eachplaquearisesfromasingleinfectiousphage.Theinfectiousparticlethatgivesrisetoaplaqueiscalledapfu(plaqueformingunit).

LysogenicorTemperatePhage

溶原性噬菌體或溫和噬菌體

Lysogenicortemperatephagesarethosethatcaneithermultiplyviathelyticcycleorenteraquiescentstateinthecell.Inthisquiescentstatemostofthephagegenesarenottranscribed;thephagegenomeexistsinarepressedstate.ThephageDNAinthisrepressedstateiscalledaprophage

becauseitisnotaphagebutithasthepotentialtoproducephage.InmostcasesthephageDNAactuallyintegratesintothehostchromosomeandisreplicatedalongwiththehostchromosomeandpassedontothedaughtercells.Thecellharboringaprophageistermedalysogenicbacterium.

Lysogenicbacterium

InductionAnimationsummarizingthelysogeniclifecycleofatemperatebacteriophage.溶原性細(xì)菌的溶原性周期和溶菌性周期Whenacellbecomeslysogenized,occasionallyextragenescarriedbythephagegetexpressedinthecell.Thesegenescanchangethepropertiesofthebacterialcell.Thisprocessiscalledlysogenicconversion.

lysogenicconversion

溶原性轉(zhuǎn)換

BacterialGenomicsMicrobialGenomics68%DeinococcusradioduransMicrobialGenomeFeaturesG+Ccontent29%BorreliaburgdorferiGenomeorganizationsinglecircularchromosomelargelinearchromosomeplus21extrachromosomalelementscircularchromosomeplusoneormoreextrachromosomalelementstwocircularchromosomesPLASMIDSPlasmidsareextrachromosomalgeneticelementscapableofautonomousreplication.AnepisomeisaplasmidthatcanintegrateintothebacterialchromosomeClassificationofPlasmidsTransferproperties

Conjugativeplasmids

NonconjugativeplasmidsPhenotypiceffects

Fertilityplasmid(Ffactor)

Bacteriocinogenicplasmids.

Resistanceplasmids7factors).Insertionsequences(IS)-Insertionsequencesaretransposablegeneticelementsthatcarrynoknowngenesexceptthosethatarerequiredfortransposition.a.Nomenclature-InsertionsequencesaregiventhedesignationISfollowedbyanumber.

e.g.IS1b.StructureInsertionsequencesaresmallstretchesofDNAthathaveattheirendsrepeatedsequences,whichareinvolvedintransposition.Inbetweentheterminalrepeatedsequencestherearegenesinvolvedintranspositionandsequencesthatcancontroltheexpressionofthegenesbutnoothernonessentialgenesarepresent.c.Importancei)Mutation-Theintroductionofaninsertionsequenceintoabacterialgenewillresultintheinactivationofthegene.ii)Plasmidinsertionintochromosomes-Thesitesatwhichplasmidsinsertintothebacterialchromosomeareatornearinsertionsequenceinthechromosome.iii)PhaseVariation-Theflagellarantigensareoneofthemainantigenstowhichtheimmuneresponseisdirectedinourattempttofightoffabacterialinfection.InSalmonellatherearetwogeneswhichcodefortwoantigenicallydifferentflagellarantigens.Theexpressionofthesegenesisregulatedbyaninsertionsequences.Inoneorientationoneofthegenesisactivewhileintheotherorientationtheotherflagellargeneisactive.Thus,Salmonellacanchangetheirflagellainresponsetotheimmunesystems'attack.PhasevariationisnotuniquetoSalmonellaflagellarantigens.Itisalsoseenwithotherbacterialsurfaceantigens.Alsothemechanismofphasevariationmaydifferindifferentspeciesofbacteria(e.g.Neisseria;transformation).Transposons(Tn)-Transposonsaretransposablegeneticelementsthatcarryoneormoreothergenesinadditiontothosewhichareessentialfortransposition.

Nomenclature-TransposonsaregiventhedesignationTnfollowedbyanumber.Structure-Thestructureofatransposonissimilartothatofaninsertionsequence.Theextragenesarelocatedbetweentheterminalrepeatedsequences.Insomeinstances(compositetransposons)theterminalrepeatedsequencesareactuallyinsertionsequences.Importance-Manyantibioticresistancegenesarelocatedontransposons.SincetransposonscanjumpfromoneDNAmoleculetoanother,theseantibioticresistancetransposonsareamajorfactorinthedevelopmentofplasmidswhichcanconfermultipledrugresistanceonabacteriumharboringsuchaplasmid.Thesemultipledrugresistanceplasmidshavebecomeamajormedicalproblembecausetheindiscriminateuseofantibioticshaveprovidedaselectiveadvantageforbacteriaharboringtheseplasmids.MechanismofbacterialvariationGenemutationGenetransferandrecombination

TransformationConjugationTransductionLysogenicconversionProtoplastfusionTypesofmutationBasesubstitutionFrameshefitInsertionsequencesWhatcancausemutation?Chemicals: nitrousacid;alkylatingagents 5-bromouracil benzpyreneRadiation:X-raysandUltravioletlightVirusesBacterialmutationMutationrateMutation

andselectivityBackwardmutationTransformationTransformationisgenetransferresultingfromtheuptakebyarecipientcellofnaked

DNAfromadonorcell.Certainbacteria(e.g.Bacillus,Haemophilus,Neisseria,Pneumococcus)

cantakeupDNAfromtheenvironmentandtheDNAthatistakenupcanbeincorporatedintothe

recipient'schromosome.

Conjugation

TransferofDNAfromadonortoarecipientbydirectphysicalcontactbetweenthe

cells.Inbacteriatherearetwomatingtypesadonor(male)andarecipient(female)andthedirection

oftransferofgeneticmaterialisoneway;DNAistransferredfromadonortoarecipient.PhysiologicalStatesofFFactorAutonomous(F+)CharacteristicsofF+xF-crossesF-becomesF+whileF+remainsF+LowtransferofdonorchromosomalgenesF+Physiological

StatesofFFactorIntegrated(Hfr)CharacteristicsofHfrxF-crossesF-rarelybecomesHfrwhileHfrremainsHfrHightransferofcertaindonorchromosomalgenesF+HfrPhysiologicalStatesofFFactorAutonomouswithdonorgenes(F’)CharacteristicsofF’xF-crossesF-becomesF’whileF’remainsF’HightransferofdonorgenesonF’andlowtransferofotherdonorchromosomalgenesHfrF’MechanismofF+xF-CrossesDNAtransferOriginoftransferRollingcirclereplicationPairformationConjugationbridgeF+F-F+F-F+F+F+F+MechanismofHfrxF-CrossesDNAtransferOriginoftransferRollingcirclereplicationHomologousrecombinationPairformationConjugationbridgeHfrF-HfrF-HfrF-HfrF-MechanismofF’