医学微生物课件(英文版)

病原生物学

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经验时期Experimentalphase实验时期Modernphase现代微生物学时期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荚膜flagella鞭毛pili菌毛spore

芽胞Essentialstructures

cellwall细胞壁

cellmembrane细胞膜

Cytoplasm细胞质

nuclearmaterial

核质Gram+Gram-CellwallCell(inner)membraneOutermembraneRibosomesGranuleCellwallNucleoidCellmembraneCapsuleFlagellumPiliGram,C.1884.UeberdieisolirteFarbungderSchizomyceteninSchnittÄundTrockenpraparaten.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:氧气、二氧化碳5.Osmoticpressure渗透压

BacterialNutritionandGrowthClassificationbasedontheirsourceofcarbon

根据细菌所利用的能源和碳源的不同，将细菌分为两大营养类型。1.Autotrophs自养菌

2.Heterotrophs异养菌:saprophytes腐生菌;parasites寄生菌

Nutrientrequirementsofbacterialgrowth:

1.Water2.Carbonsource3.Nitrogensource氮源

4.Minerals无机盐5.Growthfactors生长因子：thatacellmusthaveforgrowthbutcannotsynthesizeitself.Suchasaminoacids,purines嘌呤,pyrimidines嘧啶,andvitamins

流感嗜血杆菌X因子（高铁血红素）

V因子（辅酶Ⅰ或Ⅱ）

TemperaturePsychrophilicforms嗜冷菌

(15-20℃)

Mesophilicforms嗜温菌（30-37℃）includeallhumanpathogensandopportunists.

Thermophilicforms嗜热菌（50-60℃）

pHNeutrophiles嗜中性菌（5to8）

Acidophiles嗜酸性菌（below5.5）Alkaliphiles嗜碱性菌（above8.5）GasRequirements

Obligateanaerobes专性厌氧菌

缺乏分解有毒氧基团的酶：catalase触酶,peroxidase过氧化物酶,superoxidedismutase超氧化物歧化酶

缺乏氧化还原电势高的呼吸酶：细胞色素、细胞色素氧化酶破伤风梭菌、肉毒梭菌2O2-+

2H+SODH2O2+O2

2H2O2触酶2H2O+O2H2O2+AH2

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

BacterialGrowth

Bacteriamultiplybybinaryfission二分裂

Generationtime代时：

thetimeittakesforapopulationofbacteriatodoubleinnumbermanycommonbacteria：20~60minmostcommonpathogensinthebody：5-10hoursPopulationdynamics群体动力学--thegrowthcurve生长曲线

a.TheLagPhase迟缓期(A)

b.TheExponentialPhase指数期(C)

c.TheMaximumStationaryPhase稳定期(E)

d.TheDeathordeclinePhase衰亡期(F)

对数期迟缓期growthcurve

0515202530105.56.08.58.07.57.06.59.0衰退期总菌数活菌数细菌数的对数次小时稳定期MicrobialMetabolism

细菌的新陈代谢EnergyMetabolismMedicalImportantMetabolicProductsanabolicprocesses合成代谢

catabolicprocesses分解代谢

EnergyMetabolism1.CellularrespirationistheprocesscellsusetoconverttheenergyinthechemicalbondsofnutrientstoATPenergy.细胞呼吸是细胞将营养物质化学键中的能量转化为ATP的过程。

Aerobicrespiration需氧呼吸

Anaerobicrespiration无氧呼吸

2.Fermentation发酵

MetabolicProductsandBiochemicalTesting代谢产物和生化试验a.CarbohydrateFermentationTests糖发酵试验b.MethylRed(MR)Test甲基红试验葡萄糖→丙酮酸→乙酰甲基甲醇甲基红-葡萄糖→丙酮酸甲基红+大肠杆菌＋产气杆菌－c.Voges-Proskauer(VP)Test

葡萄糖→丙酮酸→乙酰甲基甲醇→二乙酰→红色化合物+胍基化合物葡萄糖→丙酮酸

－大肠杆菌－产气杆菌＋d.CitrateUtilizationTest枸橼酸盐利用试验

利用枸橼酸盐生长+不能利用-大肠杆菌－产气杆菌＋e.IndoleTest吲哚试验

色氨酸→吲哚→玫瑰吲哚

吲哚试剂大肠杆菌＋产气杆菌－IMViC试验VPtestCitrateutilizationtestIndoltestMethyltest

I

M

Vi

C大肠杆菌++——产气杆菌——++常用于肠道杆菌的鉴定f.Hydrogen

Sulfide(H2S

)Production硫化氢试验g.UreaseTest尿素酶试验

SyntheticProducts

a.Pyrogen热原质（致热原）Thisisafever-producingsubstancesynthesizedbybacteria.细菌合成的一种注入人体或动物体内能引起发热反应的物质。LPS/耐高温/去除方法：250℃干烤、蒸馏、吸附剂等/制备和使用注射药品过程无菌操作

b.ToxinsandInvasiveEnzyme

毒素与侵袭性酶

ExotoxinInvasiveEnzyme（侵袭性酶）c.Pigments色素

水溶性（绿脓杆菌）脂溶性（金黄色葡萄球菌）d.Antibiotics抗生素e.Bactericin细菌素

f.Vitamins维生素

ArtificialCultivationofBacteria

细菌的人工培养

Medium培养基：由人工方法配制而成的，专供微生物生长繁殖使用的混合营养物制品Classificationaccordingtobasicingredients

a.Minimalessentialgrowthmedium基础培养基b.Enrichmentmedium

增菌培养基

c.Selectivemedium选择培养基

d.Differentialmedium鉴别培养基Classificationaccordingtophysicalcondition:

a．liquidmedium

b．solidmedium

C．semisolidmedium

Phenomenaofbacterialgrowth

Inliquidmedium

表面生长

沉淀生长

混浊生长

Onplate

Semisolidmedium

无动力有动力Purposesofbacterialartificialcultivation

感染性疾病的诊断，鉴别和药敏试验生物制品的制备细菌学研究designatedbyaLatinbinominal（拉丁双名法）

前属名，后种名Staphylococcus(genus)aureus(species)

BacterialClassification科有共同血缘关系的属组成科链球菌科属性状相近关系密切的若干种组成一个菌属链球菌属种分类的基本单位，生物学基本相同的成一个种肺炎链球菌型种内的细菌根据某些差异进一步分型或亚种肺炎链球菌3型株对不同来源的同一种的细菌称青霉素耐药株界、门、纲、目、科、属、种

SomeofthefeaturesthathavebeenusedtoclassifybacteriaGramstain(cellwallstructure)

MolepercentG+Cinthegenome

Growthtemperature

Abilitytoformheatstablespores

Electronacceptorsforrespiration(ifany)

Photosyntheticability

Motility

Cellshape

Abilitytousevariouscarbonandnitrogensources

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

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

Inhibitsthegrowthofmicroorganisms.Asepsis无菌

Nolivingmicroorganismsexists.ControllingMicroorganismsByPhysicalAgentsHighTemperature

Radiation辐射Filtration过滤LowTemperatureDesiccation干燥HighTemperature

staticactioncidalactionDryheat干热：proteinoxidation

Hotairsterilization干烤

Incineration焚化redheat赤热flaming烧灼

Moistheat湿热：denatureproteinsandmeltlipids;moreeffective

Autoclaving:121℃,103.4kPa,

20min

cidalforbothvegetativeorganismsandendosporesBoilingwater煮沸灭菌

Pasteurization巴氏消毒法:tokillparticularspoilageorganismsorpathogensflashmethod瞬间法:71.6°C,15sholdingmethod持续法:62.9°C,30minfractionalsterilization间歇蒸气灭菌法

:1)Steamheatingto100°Cfor30min——常压/流动蒸气消毒法

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紫外线辐射

IonizingRadiation电离辐射

UltravioletRadiationmicrobicidalactivityofultraviolet(UV)lightdependson:lengthofexposure

wavelengthofUV:260nm-270nm

Mechanism:thymine-thyminedimmers胸腺嘧啶二聚体

photoreactivation光复活作用strongvisiblelight

verypoorpenetratingpower

damagetheeyes,causeburns,andcausemutationincellsoftheskin

IonizingRadiation电离辐射

X-raysandgammarays

moreenergyandpenetratingpowerthanUVusedtosterilizepharmaceuticalsanddisposablemedicalsuppliessuchassyringes,surgicalgloves,catheters导尿管,andsutures缝合线usedtoretardspoilageinseafoods,meats,poultry,andfruits

Filtration过滤

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结核分枝杆菌,andP.species假单胞菌.

Alcohols

denaturemembranes70%solutionsofethylorisopropylalcohol乙醇或异丙醇ineffectiveagainstendosporesandnon-envelopedviruses

AcidsandalkaliesaltermembranepermeabilityanddenatureproteinsandothermoleculesSaltsoforganicacids:foodpreservativesUndecylenicacid十一烯酸:dermatophyte皮肤真菌infections

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

Chlorine

reactswithwatertoformhypochlorite次氯酸盐

ions,whichinturndenaturemicrobialenzymes

Iodineandiodophoresdenaturesmicrobialproteinseffectiveagainstsomeendospores

Aldehydes醛denaturemicrobialproteinsFormalin福尔马林(37%aqueoussolutionofformaldehydegas)glutaraldehyde戊二醛:killvegetativebacteriain10-30minutesandendosporesinabout4hoursFactorsInfluencingAntimicrobialActivity

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

常用的化学消毒剂类别作用机制常用种类酚类蛋白变性，细胞膜损伤洗必泰醇类去除脂类，蛋白变性乙醇卤素蛋白变性氯气、碘酊、碘伏重金属盐蛋白变性红汞、硫柳汞、硝酸银醛类蛋白变性福尔马林、戊二醛表面活性剂蛋白变性，细胞膜损伤新洁而灭酸碱类染料破坏细胞膜、细胞壁，蛋白变性干扰氧化、抑制繁殖十一烯酸龙胆紫1.杀灭芽胞最常用和最有效的方法是：____________。a.紫外线照射b.煮沸5minc.巴氏消毒法d.流通蒸气灭菌法e.高压蒸气灭菌法2.灭菌方法错误的是____________。a.手术室空气-紫外线b.排泄物-漂白粉c.饮水-氯气d.含血清培养基-高压蒸气灭菌e.温度计-75%酒精3.下述不可能杀灭细菌芽胞的方法是：____________。a.煮沸法b.巴氏消毒法c.间歇灭菌法d.干热灭菌法e.高压蒸气灭菌法4.关于紫外线，说法错误的是____________。(第03章)a.其杀菌作用与波长有关b.可损坏细菌的DNA构型c.260-270nm杀菌作用最强d.其穿透力弱，故对人体无损害e.紫外线适用空气和物体表面的消毒5.____________常用于空气或物体表面的消毒。(第03章)a.高压蒸气灭菌法b.紫外线照射法c.滤过除菌法d.巴氏消毒法e.干烤法

6.____________常用于基础培养基灭菌。(第03章)a.高压蒸气灭菌法b.紫外线照射法c.滤过除菌法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二十面体

filamentousTailTailFibersBasePlateHeadContractileSheathCapsidDNATypesofBacteriophageLyticorVirulentPhages

毒性噬菌体

LysogenicorTemperatePhage

溶原性噬菌体或温和噬菌体

LyticorVirulentPhagesDefinition:

Lyticorvirulentphagesarephageswhichcanonlymultiplyinbacteriaandkillthecellbylysisattheendofthelifecycle.

LifeCycleAdsorption吸附

Penetration穿入

BiologicalSynthesis生物合成

MaturationandRelease成熟和释放

Adsorption吸附Penetration穿入

BiologicalSynthesis生物合成

MaturationandRelease成熟和释放

BacteriophagebindingtoandinjectingtheirDNAintoabacterialcellnormalbacteriophage

bacteriophageaftercontractionofsheath

AssayforLyticPhage

Plaqueassay噬斑测定

Lyticphageareenumeratedbyaplaqueassay.Aplaqueisaclearareawhichresultsfromthelysisofbacteria.Eachplaquearisesfromasingleinfectiousphage.Theinfectiousparticlethatgivesrisetoaplaqueiscalledapfu(plaqueformingunit).

LysogenicorTemperatePhage

溶原性噬菌体或温和噬菌体

Lysogenicortemperatephagesarethosethatcaneithermultiplyviathelyticcycleorenteraquiescentstateinthecell.Inthisquiescentstatemostofthephagegenesarenottranscribed;thephagegenomeexistsinarepressedstate.ThephageDNAinthisrepressedstateiscalledaprophage

becauseitisnotaphagebutithasthepotentialtoproducephage.InmostcasesthephageDNAactuallyintegratesintothehostchromosomeandisreplicatedalongwiththehostchromosomeandpassedontothedaughtercells.Thecellharboringaprophageistermedalysogenicbacterium.

Lysogenicbacterium

InductionAnimationsummarizingthelysogeniclifecycleofatemperatebacteriophage.溶原性细菌的溶原性周期和溶菌性周期Whenacellbecomeslysogenized,occasionallyextragenescarriedbythephagegetexpressedinthecell.Thesegenescanchangethepropertiesofthebacterialcell.Thisprocessiscalledlysogenicconversion.

lysogenicconversion

溶原性转换

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’