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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-iodinecomplexisretainedduringtheshortdecolorizationstepandthebac...