细菌的遗传和变异ePPT推荐.ppt
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细菌的遗传和变异ePPT推荐.ppt
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BacterialGeneticsXiao-KuiGUOPhDBacterialGenomicsMicrobialGenomics68%DeinococcusradioduransMicrobialGenomeFeaturesG+Ccontent29%BorreliaburgdorferiGenomeorganizationsinglecircularchromosomelargelinearchromosomeplus21extrachromosomalelementscircularchromosomeplusoneormoreextrachromosomalelementstwocircularchromosomesPLASMIDSPLASMIDSPlasmidsPlasmidsareareextrachromosomalextrachromosomalgeneticelementscapableofgeneticelementscapableofautonomousreplication.Anautonomousreplication.AnepisomeepisomeisaisaplasmidplasmidthatcanintegrateintothebacterialthatcanintegrateintothebacterialchromosomechromosomeClassificationofClassificationofPlasmidsPlasmidsTransferpropertiesTransferpropertiesConjugativeConjugativeplasmidsplasmidsNonconjugativeplasmidsNonconjugativeplasmidsPhenotypiceffectsPhenotypiceffectsFertilityFertilityplasmidplasmid(Ffactor)(Ffactor)BacteriocinogenicplasmidsBacteriocinogenicplasmids.ResistanceResistanceplasmidsplasmids7factors)7factors).Insertionsequences(IS)-InsertionsequencesaretransposablegeneticInsertionsequencesaretransposablegeneticelementsthatcarrynoknowngenesexceptthosethatarerequiredfortransposition.elementsthatcarrynoknowngenesexceptthosethatarerequiredfortransposition.a.a.NomenclatureNomenclature-InsertionsequencesaregiventhedesignationISfollowedbyanumber.e.g.IS1-InsertionsequencesaregiventhedesignationISfollowedbyanumber.e.g.IS1b.b.StructureStructureInsertionsequencesaresmallstretchesofDNAthathaveattheirendsrepeatedsequences,InsertionsequencesaresmallstretchesofDNAthathaveattheirendsrepeatedsequences,whichareinvolvedintransposition.Inbetweentheterminalrepeatedsequencestherearegenesinvolvedinwhichareinvolvedintransposition.Inbetweentheterminalrepeatedsequencestherearegenesinvolvedintranspositionandsequencesthatcancontroltheexpressionofthegenesbutnoothernonessentialgenestranspositionandsequencesthatcancontroltheexpressionofthegenesbutnoothernonessentialgenesarepresent.arepresent.c.c.ImportanceImportancei)Mutation-Theintroductionofaninsertionsequenceintoabacterialgenewillresultintheinactivationofi)Mutation-Theintroductionofaninsertionsequenceintoabacterialgenewillresultintheinactivationofthegene.thegene.ii)ii)PlasmidPlasmidinsertionintochromosomes-Thesitesatwhichinsertionintochromosomes-Thesitesatwhichplasmidsplasmidsinsertintothebacterialchromosomeinsertintothebacterialchromosomeareatornearinsertionsequenceinthechromosome.areatornearinsertionsequenceinthechromosome.iii)PhaseVariation-Theiii)PhaseVariation-Theflagellarflagellarantigensareoneofthemainantigenstowhichtheimmuneresponseisantigensareoneofthemainantigenstowhichtheimmuneresponseisdirectedinourattempttofightoffabacterialinfection.InSalmonellatherearetwogeneswhichcodefortwodirectedinourattempttofightoffabacterialinfection.InSalmonellatherearetwogeneswhichcodefortwoantigenicallyantigenicallydifferentdifferentflagellarflagellarantigens.Theexpressionofthesegenesisregulatedbyaninsertionantigens.Theexpressionofthesegenesisregulatedbyaninsertionsequences.Inoneorientationoneofthegenesisactivewhileintheotherorientationtheothersequences.Inoneorientationoneofthegenesisactivewhileintheotherorientationtheotherflagellarflagellargeneisactive.Thus,Salmonellacanchangetheirflagellainresponsetotheimmunesystemsattack.geneisactive.Thus,Salmonellacanchangetheirflagellainresponsetotheimmunesystemsattack.PhasevariationisnotuniquetoSalmonellaPhasevariationisnotuniquetoSalmonellaflagellarflagellarantigens.Itisalsoseenwithotherbacterialsurfaceantigens.Itisalsoseenwithotherbacterialsurfaceantigens.Alsothemechanismofphasevariationmaydifferindifferentspeciesofbacteria(e.g.antigens.Alsothemechanismofphasevariationmaydifferindifferentspeciesofbacteria(e.g.NeisseriaNeisseria;@#@transformation).transformation).Transposons(Tn)-TransposonsTransposonsaretransposablegeneticelementsaretransposablegeneticelementsthatcarryoneormoreothergenesinadditiontothosewhichareessentialforthatcarryoneormoreothergenesinadditiontothosewhichareessentialfortransposition.transposition.NomenclatureNomenclature-TransposonsTransposonsaregiventhedesignationaregiventhedesignationTnTnfollowedbyafollowedbyanumber.number.StructureStructure-Thestructureofa-Thestructureofatransposontransposonissimilartothatofaninsertionissimilartothatofaninsertionsequence.Theextragenesarelocatedbetweentheterminalrepeatedsequence.Theextragenesarelocatedbetweentheterminalrepeatedsequences.Insomeinstances(compositesequences.Insomeinstances(compositetransposonstransposons)theterminalrepeated)theterminalrepeatedsequencesareactuallyinsertionsequences.sequencesareactuallyinsertionsequences.ImportanceImportance-Manyantibioticresistancegenesarelocatedon-Manyantibioticresistancegenesarelocatedontransposonstransposons.SinceSincetransposonstransposonscanjumpfromoneDNAmoleculetoanother,thesecanjumpfromoneDNAmoleculetoanother,thesea
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- 细菌 遗传 变异