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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’
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