微生物学英文题库

IntroductionMicrobesareadiversegroupoforganismsthatcanbedividedintotheviruses,unicellulargroups(Archaea,Eubacteria,protista,somefungiandsomechlorophyta)andasmallnumberoforganismswithasimplemulticellularstructure(thelargefungiandchlorophyta).Microbiology:thescience(logos)ofsmall(micro)life(bios).Thestudyoflivingthingssosmallthattheycannotbeseenwiththenakedeye.Thethree-domainsystemisabiologicalclassificationintroducedbyCarlWoesethatdividescellularlifeformsintoarchaea,bacteria,andeukaryotedomains.Inparticular,itemphasizestheseparationofprokaryotesintotwogroups,originallycalledEubacteria(nowBacteria)andArchaebacteria(nowArchaea).MicroorganismswerefirstvisualizedbyAntonivanLeeuwenhoek(1632–1723),aDutchclothmerchantandanexpertlensgrinder.ThefirstproofoftheinvolvementofbacteriaindiseaseandthedefinitiveproofofthegermtheoryofdiseasecamefromtheGermanRobertKoch.Koch’spostulates:1,Themicroorganismmustbepresentineveryinstanceofthediseaseandabsentfromhealthyindividuals.2,Themicroorganismmustbecapableofbeingisolatedandgrowninpureculture.3,Whenthemicroorganismisinoculatedintoahealthyhost,thesamediseaseconditionmustresult.4,Thesamemicroorganismmustbere-isolatedfromtheexperimentallyinfectedhost.ChapteroneFungiincludeyeasts,molds,andmushrooms.Virusesarenoncellularorganisms;theyareintra-cellularparasitesofanimals,plants,orbacteria.1,TheProkaryotescanbedividedintotwokingdoms,BacteriaandArchaea.TheclassificationwasfirstproposedbyWoesebasedonthedifferencesin16SrRNAsequence.2,Prokaryoticmicroorganism（原核微生物）:Itisansingle-celledorganismwhichdoesn’thaveanuclearmembraneoutsidethecellnucleusandonlyhasthebareDNAcalledasthenucleararea.3,Manybacteriaareshapedlikelongrodstwistedintospiralsorhelices;theyarecalledspirilla（螺旋菌）ifrigidandspirochetes(螺旋体)whenflexible.4,Capsules(荚膜)andslimelayers(粘液层)usuallyarecomposedofpolysaccharides(多糖),buttheymaybeconstructedofothermaterials.5,Gramstainingprocedure(革兰氏染色的步骤)InthefirststepoftheGram-stainingprocedure,thesmearisstainedwiththebasicdyecrystalviolet,theprimarystain.Itisfollowedbytreatmentwithaniodinesolutionfunctioningasamordant.Thatis,theiodineincreasestheinteractionbetweenthecellandthedyesothatthecellisstainedmorestrongly.Thesmearisnextdecolorizedbywashingwithethanoloracetone.ThisstepgeneratesthedifferentialaspectoftheGramstain;gram-positivebacteriaretainthecrystalviolet,whereasgram-negativebacterialosetheircrystalvioletandbecomecolorless.Finally,thesmeariscounterstainedwithasimple,basicdyedifferentincolorfromcrystalviolet.Safranin,themostcommoncounterstain,colorsgram-negativebacteriapinktoredandleavesgram-positivebacteriadarkpurple.6,TheMechanismofGramStaining（革兰氏染色的机制）AlthoughseveralexplanationshavebeengivenfortheGramstainreactionresults,itseemslikelythatthedifferencebetweengram-positiveandgram-negativebacteriaisduetothephysicalnatureoftheircellwalls.Ifthecellwallisremovedfromgrampositivebacteria,theybecomegramnegative.Thepeptidoglycanitselfisnotstained;insteaditseemstoactasapermeabilitybarrierpreventinglossofcrystalviolet.Duringtheprocedurethebacteriaarefirststainedwithcrystalvioletandnexttreatedwithiodinetopromotedyeretention.Whengram-positivebacteriathenaredecolorizedwithethanol,thealcoholisthoughttoshrinktheporesofthethickpeptidoglycan.Thusthedye-iodinecomplexisretainedduringtheshortdecolorizationstepandthebacteriaremainpurple.Incontrast,gram-negativepeptidoglycanisverythin,notashighlycross-linked,andhaslargerpores.Alcoholtreatmentalsomayextractenoughlipidfromthegramnegativewalltoincreaseitsporosityfurther.Forthesereasons,alcoholmorereadilyremovesthepurplecrystalviolet-iodinecomplexfromgram-negativebacteria.简而言之，不同细菌的染色差异（G+或G-）是由于细胞壁化学成分的差异而引起了物理特性（脱色能力）的不同。具体而言：通过初染和媒染后，在细胞膜内形成了不溶于水的结晶与碘的复合物。G+菌由于细胞壁厚，肽聚糖网层次多而交联紧密，并且不含类脂，故以乙醇脱色时不会溶出缝隙，反而使肽聚糖网孔收缩，使染料滞留在细胞壁内而使其染上紫色；反之，G-菌由于细胞壁薄，外膜层类脂含量高，肽聚糖层薄和交联度差，当遇到乙醇时，以类脂为主的的外膜迅速溶解，这时薄而松散的肽聚糖网不能阻挡结晶紫与碘的复合物的溶出，故细胞退成无色。再经番红等红色染料复染时，就使G-菌呈现红色，而G+菌仍保留紫色或紫红色。图示革兰氏阳性菌和革兰氏阴性菌细胞壁结构。试述革兰氏阳性菌和革兰氏阴性菌肽聚糖单体的异同点。（1）四肽尾的第3个氨基酸不是L-lys，而是被内消旋二氨基二酸（m-DAP）所代替（2）没有特殊的肽桥，其前后两个单体间的连接仅通过甲四肽尾的第4个氨基酸-D-Ala的羧基与乙四肽尾的第3个氨基酸-m-DAP的氨基直接相连。Endospore(芽孢)：某些细菌在其生长发育后期，在细胞内形成一个圆形或椭圆形、厚壁、含水量极低、抗逆性极强的休眠体，称为芽孢。芽孢的结构：Endospore-formingprocess(芽孢的形成过程)鞭毛（flagellum）的结构分为基体、钩形鞘和螺旋丝;革兰氏阴性菌（G-）基体由L、P、S、M四个环构成;革兰氏阴性菌（G+）基体由2个环构成。ThesystemictaxaofmocroorganismsfollowthesystemictaxabuiltbyLinnaeus，includingsevengradesfromtoptobottom:KingdomPhylumClassOrderFamilyGenusSpeciesAllspeciesnamesofcellularmicroorganismsobeytheLatinbinominalnomenclaturebuiltbyLinnaeuswithoutexception.Mycoplasma(支原体)aretheprocaryoticorganismbetweenbacteria(细菌)andrickettsia(立克次氏体).Chlamydia(衣原体)areagenusofminitypeGram-negativeprokaryoticorganismwhichobligateparasitizeineukaryoticcells.SpirochaetaareagroupofGram-negativeunicellularprokaryoticorganismwhoseconfigurationandkinesiologyareparticular.SubstratemyceliumAerialhyphaeSporularhyphaMajorCharacteristicsUsedinTaxonomy：1，ClassicalCharacteristicsMorphologicalCharacteristicsPhysiologicalandMetabolicCharacteristicsEcologicalCharacteristicsGeneticAnalysis2,MolecularCha