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3,Whenthemicroorganismisinoculatedintoahealthyhost,thesamediseaseconditionmustresult.
4,Thesamemicroorganismmustbere-isolatedfromtheexperimentallyinfectedhost.
Chapterone
Fungiincludeyeasts,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:
KingdomPhylumClassOrderFamilyGenusSpecies
AllspeciesnamesofcellularmicroorganismsobeytheLatinbinominalnomenclaturebuiltbyLinnaeuswithoutexception.
Mycoplasma(支原体)aretheprocaryoticorganismbetweenbacteria(细菌)andrickettsia(立克次氏体).
Chlamydia(衣原体)areagenusofminitypeGram-negativeprokaryoticorganismwhichobligateparasitizeineukaryoticcells.
SpirochaetaareagroupofGram-negativeunicellularprokaryoticorganismwhoseconfigurationandkinesiologyareparticular.
SubstratemyceliumAerialhyphaeSporularhypha
MajorCharacteristicsUsedinTaxonomy:
•1,ClassicalCharacteristics
•MorphologicalCharacteristics
•PhysiologicalandMetabolicCharacteristics
•EcologicalCharacteristics
•GeneticAnalysis
•2,MolecularCharacteristics
•ComparisonofProteins
•NucleicAcidBaseComposition
•NucleicAcidHybridization
•NucleicAcidSequencing(16SrRNAsequencing)
Bacterialcolony(菌落):
Abacterialcolonyisdefinedasavisibleclusteroforganismsgrowingonthesurfaceoforwithinasolidmedium,theoreticallyculturedfromasinglecell.
Bacteriallawn(菌苔):
Bacteriallawnisausedbybiologiststodescribetheappearanceofbacterialcolonieswhenalltheindividualcoloniesonapetri-dishmergetogethertoformaafieldormatofbacteria.
Eukaryoticcell
Eukaryoticmicroorganisms(真核微生物概念):
Theeukaryoticmicroorganismsisnotanaturalmonophyletictaxon.Theyhavethenuclearmembranecoatingacellnucleus,carryoutmitosis,andhavemitochondriainthecytoplasm.
Eukaryoticmicroorganismsinclude:
fungi,microalgaeandprotozoa.
Fungidifferfromplantsintwoquitefundamentalrespects:
*Plantsobtainenergyfromthesun,fungidonot;
*PlantsutilizeCO2asacarbonsource,fungidonot.
Oneofthefeaturesthatcausedtaxonomistsfinallytoremovefungifromtheplantkingdomwasthedistinctivechemicalnatureofthefungalcellwall.Whereasplantandalgalcellshavewallscomposedofcellulose,thecellwalloffungiismadeupprincipallyofchitin.
Fungi(真菌的概念):
Thistermfungusindicatesthoseorganismsthathavetruenucleus,producesporesbyasexualorsexualreproduction,absorbthenourishmentmaterial,havenochloroplast.Membersoffungiincludeyeast,moldandmushroom.
Majorcharactersoffungi:
①Witharealnucleus;
②Havingnochloroplastandphotosynthesis;
③Vegetativebodiesareusuallydevelopingfilamentousandbranchedstructureaswellasunicell;
④Typicallyformingasexualandsexualreproductivespores;
⑤Containingchitininthecellwall;
⑥Heterotrophybyabsorption;
⑦Morelivingadaptivelyintheland.
Somefungihavelong,branched,threadlikefilamentscalledhyphae(菌丝),whichaggregatetogethertoformatangledmycelium(菌丝体).Insomefungithehyphaehavecrosswallscalledsepta(横隔)separatingcells,whichmayneverthelessbejoinedbyoneormorepores,whichpermitcytoplasmicstreaming,aformofinternaltransport.
Fungiarecategorizedintophyla(divisions)basedonthetypeofstructuresproducedduringsexualreproduction.
(1)Chytridiomycota(壶菌亚门,低等真菌)
(2)Zygomycota(接合菌亚门,低等真菌)
(3)Ascomycota(子囊菌亚门,高等真菌)
(4)Basidiomycota(担子菌亚门,高等真菌)
(5)Deuteromycota(半知菌亚门,高等真菌)
真菌的分类(Ainsworth分类系统)依据:
横隔有无,无性孢子,有性孢子,典型的代表微生物种类,自己列表。
有性孢子的种类和比较(见PPT),无性孢子的种类和比较(见PPT),有性繁殖的三个过程。
rhizoid(假根);
Haustorium(吸器)
Lifecycleoffungi:
Ingeneral,thelifecycleinvolvesthefusionofhyphaefromtwoindividuals,formingamyceliumthatcontainshaploidnucleiofbothindividuals.Thefusionofhyphaeiscalledplasmogamy.Thefusedhyphaecontaininghaploidnucleifromtwoindividualsisheterokaryotic.Insomecases,plasmogamyresultsincellswithonenucleusfromeachindividual.Thisconditioniscalleddikaryotic.Eventually,twonucleithatoriginatedfromdifferentindividualsfusetoformadiploidzygote.Meiosisthenproduceseitherfourhaploidnucleiorfourhaploidcells.
Asexualspores(无性孢子)areformedbytheaerialmyceliumofoneorganism.Whenthesesporesgerminate,theybecomeorganismsthataregeneticallyidenticaltotheparent.
Sexualspores(有性孢子)resultfromthefusionofnucleifromtwooppositematingstrainsofthesamespeciesoffungus.Organismsthatgrowfromsexualsporeswillhavegeneticcharacteristicsofbothparentalstrains.
Virus
Virus(病毒的概念):
Virusesareauniquegroupoftinyinfectiousparticlesthatareobligateparasitesofcells,arenotcellsbutresemblecomplexmoleculescomposedofDNAorRNA.Mostofthemaresosmall(0.02-0.3µ
m)thatanelectronmicroscopeisnecessarytodetectthem.
Structuresofviruses:
nakedvirus(nucleicacid,capsid);
envelopedvirus(nucleicacid,capsidandenvelope).
Viralcapsidshavethreedifferentforms:
helicalsymmetry,icosahedralsymmetryandcomplexsymmetry.
噬菌体(phage):
侵染细菌的微生物病毒。
烈性噬菌体(virulentphages):
病毒感染宿主细胞,能在宿