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ID:50912962
大小:12.71 MB
页数:78页
时间:2020-03-15
《华中农业大学微生物英文版课件2.ppt》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、Chapter2CellBiology2.1Overviewofthestructureofmicrobialcells2.2Procaryoticcellwall2.3Cytoplasmicmembrane2.4Cellulargeneticinformation2.5Cytoplasmicmatrix–RibosomeandInclusions2.6Componentsexternaltothecellwall2.7Bacterialendospores2.8Comparisonoftheprokaryoticandeukar
2、yoticcellChapteroutlineAprocaryoticcellAeucaryoticcellOverviewofcellstructure3.TheircellwallalmostalwayscontainthecomplexpolysaccharidepeptidoglycanTheprokaryoticcell1.Theirgeneticmaterial(DNA)isnotenclosedwithinamembraneandtheylackothermembrane–boundedorganelles2.The
3、irDNAisnotassociatedwithhistidine4.Theyareverysmall!!Size:Mostbacteriafallwithinarangefrom0.2to2.0umindiameterandfrom2to8uminlengthArod-shapedprokaryoteistypicallyabout1-5micrometers(μm)longandabout1μmwideMicroorganismsingeneralareverysmallandarecompletelyinvisibletot
4、henakedeye.Acyanobacterium8x50umsizecomparisonofmicroorganismsVisibilityscaleMetersRelativesizeofMicrobesProkaryotesEukaryotesVirusesNakedeyeLightmicroscopeElectronmicroscopeacellincreasesinsize,itssurfacearea–to–volumeratiodecreasesSurfaceareaandvolumerelationshipsin
5、cellsspirallumShape:BacteriahaveafewbasicshapessphericalcoccusRod-shapedbacillusThecellwallofthebacterialcellisacomplex,semi-rigidstructurethatisresponsibleforthecharacteristicshapeofthecell.Thecellwallsurroundstheunderlying,fragileplasma(cytoplasmic)membraneandprotec
6、tsitandinternalpartsofthecellfromadversechangesinthesurroundingenvironment.Almostallprokaryoteshavecellwalls.ProkaryoticcellwallGram+Gram-SchematicdiagramofbacterialcellwallsBacteriacanbedividedintotwomajorgroups,calledgram-positiveandgram-negative.Theoriginaldistinct
7、ionbetweengram-positiveandgram-negativewasbasedonaspecialstainingprocedure,theGramstainTheGram-positivecellwallhasapeptidoglycanlayerthatisrelativelythick(ca.40nm)andcomprisesapproximately90%ofthecellwall.ThecellwallsofmostGram-positiveeubacteriaalsohaveteichoicacids.
8、Gram-positivecellwallStructureoftheRepeatingUnitinPeptidoglycanTheseconstituentsareconnectedtoformarepeatingstructure,thegly
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