细菌的形态学检查.ppt

★TheGramreactionTheGramreactionisnamedaftertheDanishphysician,ChristianGram,whodevelopedthisstainingtechniquein1884.Itinvolvesaseriesofsimplesteps.1.???Bacterialcellsaredriedontoaglassslideandstainedwithcrystalviolet,thenwashedbrieflyinwater.2.???Iodinesolutionisaddedsothattheiodineformsacomplexwithcrystalvioletinthecells.3.???Alcoholoracetoneisaddedtosolubilisethecrystalviolet-iodinecomplex.4.???Thecellsarecounterstainedwithsafranin,thenrinsedanddriedformicroscopy.Themethodseparatesbacteriaintotwotypes.Gram-positivecellsretainthecrystalviolet-iodinecomplexandthusappearpurple(shownforBacilluscereusintheleft-handimagebelow).Gram-negativecellsaredecolourisedbythealcoholoracetonetreatment,butarethenstainedwithsafraninsotheyappearpink(shownforPseudomonasaeruginosaintheright-handimagebelow).Thus,theessentialdifferencebetweenGram-positiveandGram-negativecellsistheirabilitytoretainthecrystalviolet-iodinecomplexwhentreatedwithasolvent.★hisdifferenceinstainingreflectsafundamentaldifferenceintheorganisationofthebacterialcellwallorcellenvelope,showninhighlysimplifiedformbelow.C.Gram，1884年创立，是最重要的染色法。革兰氏染色的原理:从上图可知，甲、乙两种细菌经结晶紫初染后，分别染上了紫色，经碘液媒染，结晶紫与碘液形成了分子量较大的复合物，在乙醇脱色时，凡是染上的紫色容易被脱掉的细胞又成为无色菌体（如乙菌），反之则仍为紫色（如甲菌）。最后再用红色染料——沙黄复染，结果甲菌仍然维持最初染上的紫色，而乙菌则被复染而成红色，前者称为革兰氏阳性细菌，简称G+菌，后者则称为革兰氏阴性细菌，简称G-菌。

革兰氏染色是细菌分类鉴定的重要指标，通过革兰氏染色，可以将几乎所有细菌分成革兰氏阳性细菌和革兰氏阴性细菌两大类。这两大类细菌在细胞结构、成分、形态、生理、生化、遗传、免疫、生态和药物敏感性等方面都呈现出明显的差异，因此任何细菌只要先通过很简单的革兰氏染色，即可提供不少其他重要的生物学特性方面的信息。Gram,whoinventedthegram-stainingmethodin1884.Togramstain,aninvestigatorsmearsasampleofbacteriaonaslide,soaksitinavioletdyeandthentreatsitwithiodine.Theslideisthenrinsedwithalcoholandcounterstainedwithapinkdyecalledsafranine.Thecellwallsofgram-negativebacteriahaveaverylowaffinityforthevio