华中农业大学微生物学第二章

Chapter2

CellBiology本文档共92页；当前第1页；编辑于星期二\10点48分

2.1Overviewofthestructureofmicrobialcells2.2Procaryoticcellwall2.3Cytoplasmicmembrane2.4Cellulargeneticinformation2.5Cytoplasmicmatrix–RibosomeandInclusions2.6Componentsexternaltothecellwall2.7Bacterialendospores2.8ComparisonoftheprokaryoticandeukaryoticcellChapterOutline本文档共92页；当前第2页；编辑于星期二\10点48分ConceptsProkaryotesaresmallandsimpleinstructurewhencomparedwitheukaryotes,yettheyoftenhavecharacteristicshapeandsize.

Prokaryoticgeneticmaterialislocatedinanareacalledthenucleoidandisnotenclosedbyamembrane.Theprokaryoticcellwallalmostalwayshaspeptidoglycanandischemicallyandmorphologicallycomplex.本文档共92页；当前第3页；编辑于星期二\10点48分AprocaryoticcellAeucaryoticcell2.1OverviewofCellStructure本文档共92页；当前第4页；编辑于星期二\10点48分3.TheircellwallalmostalwayscontainthecomplexpolysaccharidepeptidoglycanTheProkaryoticCell1.Theirgeneticmaterial(DNA)isnotenclosedwithinamembraneandtheylackothermembrane–boundedorganelles2.TheirDNAisnotassociatedwithhistidine4.Theyareverysmall!!本文档共92页；当前第5页；编辑于星期二\10点48分Schematicdiagramofabacterialcell本文档共92页；当前第6页；编辑于星期二\10点48分Size:

Mostbacteriafallwithinarangefrom0.2to2.0umindiameterandfrom2to8uminlengthArod-shapedprokaryoteistypicallyabout1-5micrometers(μm)longandabout1μmwideMicroorganismsingeneralareverysmallandarecompletelyinvisibletothenakedeye.

Acyanobacterium8x50um本文档共92页；当前第7页；编辑于星期二\10点48分sizecomparisonofmicroorganismsVisibility

scaleMeters

RelativesizeofMicrobesProkaryotesEukaryotesVirusesNakedeyeLightmicroscopeElectronmicroscope本文档共92页；当前第8页；编辑于星期二\10点48分acellincreasesinsize,itssurfacearea–to–volumeratiodecreasesSurfaceareaandvolumerelationshipsincells本文档共92页；当前第9页；编辑于星期二\10点48分spirallumShape:

Bacteriahaveafewbasicshapesspherical

coccusRod-shaped

bacillus本文档共92页；当前第10页；编辑于星期二\10点48分2.2ProkaryoticCellWallCellWall本文档共92页；当前第11页；编辑于星期二\10点48分Thecellwallofthebacterialcellisacomplex,semi-rigidstructurethatisresponsibleforthecharacteristicshapeofthecell.Thecellwallsurroundstheunderlying,fragileplasma(cytoplasmic)membraneandprotectsitandinternalpartsofthecellfromadversechangesinthesurroundingenvironment.Almostallprokaryoteshavecellwalls.本文档共92页；当前第12页；编辑于星期二\10点48分Gram+Gram-SchematicdiagramofbacterialcellwallsBacteriacanbedividedintotwomajorgroups,calledgram-positiveandgram-negative.Theoriginaldistinctionbetweengram-positiveandgram-negativewasbasedonaspecialstainingprocedure,theGramstain本文档共92页；当前第13页；编辑于星期二\10点48分TheGram-positivecellwallhasapeptidoglycanlayerthatisrelativelythick(ca.40nm)andcomprisesapproximately90%ofthecellwall.ThecellwallsofmostGram-positiveeubacteriaalsohaveteichoicacids.Gram-positiveCellWall本文档共92页；当前第14页；编辑于星期二\10点48分StructureoftheRepeatingUnitinPeptidoglycanTheseconstituentsareconnectedtoformarepeatingstructure,theglycantetrapeptide.Peptidoglycaniscomposedoftwosugarderivatives,N-acetylglucosamine(NAG)andN-acetylmuramicacid(NAM),andasmallgroupofaminoacidsconsistingofL-alanine,D-alanine,D-glutamicacid,andeitherlysineordiaminopimelicacid(DAP).本文档共92页；当前第15页；编辑于星期二\10点48分本文档共92页；当前第16页；编辑于星期二\10点48分Peptideandglycanunitsareconnectedinformationofthepeptidoglycansheet本文档共92页；当前第17页；编辑于星期二\10点48分Gram-positiveBacteriafrequentlyhaveacidicpolysaccharidescalledteichoicacidsattachedtotheircellwall.Thetermteichoicacidsincludesallwall,membrane,orcapsularpolymerscontainingglycerophosphateorribitolphosphateresidues.ThesepolyalcoholsareconnectedbyphosphateestersandusuallyhaveothersugarsandD-alanineattached.

TeichoicAcids本文档共92页；当前第18页；编辑于星期二\10点48分Teichoicacidsandlipoteichoicacidsarearrangedintheoverallwallstructureofgram-positiveBacteria.TeichoicacidLipoteichoicacid本文档共92页；当前第19页；编辑于星期二\10点48分TheGram-negativecellwallisathinlayerattachedtoanoutermembranevialipoproteins.Theoutermembranecontains

phospholipidonitsinnersurfaceand

lipopolysaccharide(LPS)

on

itsoutersurface.Thespacebetweentheoutermembraneandthe

cytoplasmicmembraneiscalledthe

periplasmicspace.Teichoic

acidsdonotoccurinGram-negativebacterialcellwalls..

本文档共92页；当前第20页；编辑于星期二\10点48分本文档共92页；当前第21页；编辑于星期二\10点48分OsidechainCorepolysaccharideLipidAChemicalStructureofLipopolysaccharide本文档共92页；当前第22页；编辑于星期二\10点48分MolecularModelofE.coliLipopolysaccharide本文档共92页；当前第23页；编辑于星期二\10点48分Thebondsbetweenthecarbohydratesinpseudopeptidoglycanare

β1-3insteadof'β1-4

asinpeptidoglycan.

CellWallsofArchaebacteriaThearchaebacteria

donotcontainpeptidoglycan

intheircellwallsasoccursineubacteria.N-acetylmuramicacidandD-aminoacids

arenotfound

inthecellwallsofarchaebacteria.(Differencesfromeubacteria)本文档共92页；当前第24页；编辑于星期二\10点48分Somearchaebacteriahavewallscomposedof

pseudopeptidoglycan,

whichresemblesthepeptidoglycanofeubacteriabut

containsN-acetyltalosaminuronicacid

insteadofN-acetylmuramicacidand

L.-aminoacids

insteadoftheD-aminoacidsineubacterialcellwalls.本文档共92页；当前第25页；编辑于星期二\10点48分ProtoplastFormation

Peptidoglycancanbedestroyedbycertainagentsforinstancelysozyme,thatbreaksthe1,4-glycosidicbondsbetweenN-acetylglucosamineandN-acetylmuramicacidinthemolecule.本文档共92页；当前第26页；编辑于星期二\10点48分Thedifferencebetweengram-positiveandgram-negativebacteriaisduetothephysicalnatureoftheircellwalls.Ifthecellwallisremovedfromgram-positivebacteria,theybecomegramnegative.

本文档共92页；当前第27页；编辑于星期二\10点48分Thepeptidoglycanseemstoactasapermeabilitybarrierpreventinglossofcrystalviolet.Gram-negativepeptidoglycanisverythin,notashighlycross-linked,andhaslargerpores.Alcoholtreatmentalsomayextractenoughlipidfromthegramnegativewalltofurtherincreaseitsporosity.Forthesereasons,alcoholmorereadilyremovesthepurplecrystalviolet-iodinecomplexfromgram-negativebacteria.TheMechanismofGramStaining本文档共92页；当前第28页；编辑于星期二\10点48分

ProceduresofGramStaining本文档共92页；当前第29页；编辑于星期二\10点48分GrampositiveorGramnegative?本文档共92页；当前第30页；编辑于星期二\10点48分本文档共92页；当前第31页；编辑于星期二\10点48分Structureofcytoplasmicmembrane2.3CytoplasmicMembraneFunctionofcytoplasmicmembraneMembrane本文档共92页；当前第32页；编辑于星期二\10点48分B.

Colorizedelectronmicrographof'thecytoplasmicmembrane(CM)ofthebacteriumBacillussubtilis

revealsthecharacteristicrailroadtrackappearanceofthislipidbilayer.

StructureofCytoplasmicMembraneItisatypicalUNITMEMBRANE!A.

Thetypicalcytoplasmicmembraneofprokaryoticandeukaryoticcellsisalipidbilayer,asillustratedhereshowingtheorientationsofthehydrophilic(tanspheres)andhydrophobic(black)endsofphospholipidsthatmakeupthisstructure.本文档共92页；当前第33页；编辑于星期二\10点48分Thecytoplasmicmembrane,ahighlyselectivebarrier,isconstructedprincipallyoflipid,withinwhichcertainproteinsareembedded.Membranescontainboth

lipidsandproteins,althoughtheexactproportionsoflipidandproteinvarywidely.本文档共92页；当前第34页；编辑于星期二\10点48分Diagramofthestructureofcytoplasmicmembrane本文档共92页；当前第35页；编辑于星期二\10点48分3.Energyconservation-siteofgenerationanduseoftheprotonmotiveforce.

FunctionofMembrane1.Permeabilitybarrier

-preventsleakageandfunctionasgatewayfortransportofnutrientsintoandoutofthecell.2.Proteinanchor-siteofmanyproteinsinvolvedintransport,bioenergetics,andchemotaxis.本文档共92页；当前第36页；编辑于星期二\10点48分

Rateofpermeability*

100

0.1

0.001

0.001

0.000001

0.0000001

0.00000001

Substance

Water

Glycerol

Tryptophan

Glucose

Chlorideion(Cl-)

Patassiumion(K+)

Sodiumion(Na+)

*Relativerate:Permeabilitywithrespecttopermeabilityofwatergivenas100

Comparativepermeabilityofmembranemoleculestovarious

本文档共92页；当前第37页；编辑于星期二\10点48分IntracellularMembraneSystemBacteriacellsdon’tcontainmembrane-enclosedorganelles.However,bacteriamayhavespecializedinvaginationsofthecytoplasmicmembrane.Theirfunctionmaybetoprovidealargermembranesurfaceforgreatermetabolicactivity.本文档共92页；当前第38页；编辑于星期二\10点48分StructureofMesosomeMesosomemaybeinvolvedin

wallformation

duringdivisionorplayarolein

chromosomereplication

anddistributiontodaughtercells.Itmayalsobeinvolvedin

secretoryprocesses本文档共92页；当前第39页；编辑于星期二\10点48分2.4CellularGeneticInformationNucleoid本文档共92页；当前第40页；编辑于星期二\10点48分BacterialChromosomeSupercoilingandchromosomestructureChromosomalcopynumber2.Plasmids本文档共92页；当前第41页；编辑于星期二\10点48分Micrographofabacteriumshowingthenucleoidregion(green)withinthecytoplasmwherethebacterialchromosomeoccurs本文档共92页；当前第42页；编辑于星期二\10点48分ThebacterialchromosomeisacircularDNAmacromoleculeexcept

inStreptomyces

whereitislinearand

Rhodobacter

sphaffoides,whichhastwoseparatechromosomes.

BacterialChromosomeThebacterialchromosomeisusuallya

singlecovalentlyclosedcircular

molecule.Theterm

nucleoidisusedtodescribeaggregatedDNAintheprokaryoticcell.本文档共92页；当前第43页；编辑于星期二\10点48分Rangeofgenomesizesinvirousgroupsoforganismsandtheorganellesofeukarya本文档共92页；当前第44页；编辑于星期二\10点48分Thebacterialchromosomeandsupercoiling:本文档共92页；当前第45页；编辑于星期二\10点48分ExampleofE.colicellThereareover50supercoileddomain

intheE.colichromosome.ThetotalamountofDNAisabout

4600kb.IfthetotalDNAisopenedandlinearized,itwouldbe

1mminlength.Thethecellisonly

about2-3umlong.

SotopackagethismuchDNAintothecellrequiresthat

theDNAbehighlysupercoiled.本文档共92页；当前第46页；编辑于星期二\10点48分ElectronmicrographofanisolatednucleoidreleasedfromE.coli.

本文档共92页；当前第47页；编辑于星期二\10点48分Chromosomecopynumber

Bacteriathatreproduceasexuallyaretypically

haploid

ingeneticcomplement.Rapidlygrowingcellscontain

morethan

1copy

ofthechromosome,andonlywhencellgrowthhasceaseddoesthechromosomenumberapproachonepercell.本文档共92页；当前第48页；编辑于星期二\10点48分

Reproductionofabacterialcellrequiresthereplicationofthebacterialchromosome.ThemicrographshowsthesequenceofsynthesisofnewcircularloopsofdoublehelicalDNA.Bacterianormallyreproducebybinaryfission.Theinwardgrowthoftheseptumdividestheparentcelltoproducetwoequal-sizedprogenycells.本文档共92页；当前第49页；编辑于星期二\10点48分Plasmidsdon’tcontainthegeneticinformationfortheessentialmetabolicactivitiesofthecell,buttheygenerallydocontaingeneticinformationforspecialfeatures.

PlasmidProkaryoticcellshavesmallextra-chromosomal

geneticelementscalled

plasmids.本文档共92页；当前第50页；编辑于星期二\10点48分ResistantplasmidsColplasmidsConjugativeplasmidsMetabolicplasmids

MajorTypesofPlasmids本文档共92页；当前第51页；编辑于星期二\10点48分2.5CytoplasmicMatrixRibosomeandInclusionsRibosomeCarbonstoragepolymers–PHBandglycogenPhosphatepolymersSulfurGranulesGasVacuoles本文档共92页；当前第52页；编辑于星期二\10点48分Alleucaryoticandprocaryoticcellscontainribosomes,whichfunctionasthesitesofproteinsynthesis.Ribosomesarecomposedoftwosubunits

Procaryoticribosomesarecalled70Sribosomes,andthoseofeucaryoticcellsareknownas80Sribosomes

RibosomesTheletterSreferstoSvedbergunits,whichindicatetherelativerateofsedimentationduringultra-high-speedcentrifugation本文档共92页；当前第53页；编辑于星期二\10点48分本文档共92页；当前第54页；编辑于星期二\10点48分

Withinthecytoplasmofprocaryotic(andeucaryotic)cellsareseveralkindsofreservedeposits,knownasinclusions.Someinclusionsarecommontoawidevarietyofbacteria,whereasothersarelimitedtoasmallnumberofspeciesandthereforeserveasabasisforidentification.Amongthemoreprominentbacterialinclusionsarethefollowing:InclusionCarbonstoragepolymers–PHBandglycogenPhosphatepolymersSulfurGranulesGasVacuoles本文档共92页；当前第55页；编辑于星期二\10点48分Polyhydroxybutyricacid(PHB)PHBisa

lipidlikecompound

-oneofthemostcommoninclusionbodiesinprokaryoticorganisms.PHBiscommonlyfoundasastoragematerialand

uniquetobacteria

Glycogenisa

starchlikepolymer

ofglucosesubunits.GlycogengranulesareusuallysmallerthanPHBgranules.AVibriospecies本文档共92页；当前第56页；编辑于星期二\10点48分Manymicroorganismsaccumulategranulesofpolyphosphate,whicharelargereservesof

inorganicphosphates

thatcanbeusedinthesynthesisofATPPolyphosphategranule

inabacterialcellAPseudomonasspecies本文档共92页；当前第57页；编辑于星期二\10点48分ThesulfurglobulesinsidethecellsofpurplesulfurbacteriumChromatiumbuderiSomebacteria,includingmanyphotosyntheticbacteria,accumulate

elementalsulfurgranules

asaresultoftheirmetabolism.本文档共92页；当前第58页；编辑于星期二\10点48分Gasvacuoles(blue)andstoragegranules(red)inthecyanobacteriumMicrocystisTheformationofgasvacuolesbyaquaticbacteriaprovidesamechanismforadjustingthebuoyancyofthecell.Manyaquaticcyanobacteriausetheirgasvacuolestomoveupanddowninthewatercolumn.本文档共92页；当前第59页；编辑于星期二\10点48分2.6ComponentsexternaltothecellwallFlagellaFimbriaeandpiliCapsulesandslimelayers本文档共92页；当前第60页；编辑于星期二\10点48分Motilityallowsthecelltoreachdifferentregionsofitsenvironment.Inthestruggleforsurvival,movementtoanewlocationmaymeanthedifferencebetweensurvivalanddeathofthecell.But,asinanyphysicalprocess,cellmovementiscloselytiedtoanenergyexpenditure,andthemovementofflagellaisnoexception.

Manyprokaryotesaremotile,andthisabilitytomoveindependentlyisusually

duetoaspecialstructure,

the

flagellum

(plural,flagella).

本文档共92页；当前第61页；编辑于星期二\10点48分本文档共92页；当前第62页；编辑于星期二\10点48分Fourbasictypesofflagellararrangementsa.monotrichousb.amphitrichousc.

lophotrichousd.peritrichous本文档共92页；当前第63页；编辑于星期二\10点48分Flagellaarearrangeddifferentlyondifferentbacteria.Inpolarflagellationtheflagellaareattachedatoneorbothendsofthecell.Occasionallyatuft(group)offlagellamayariseatoneendofthecell,anarrangementcalledlophotrichous.Inperitrichousflagellationtheflagellaareinsertedatmanyplacesaroundthecellsurface(perimeans"around").Thetypeofflagellation,polarorperitrichous,isoftenusedasacharacteristicintheclassificationofbacteria.本文档共92页；当前第64页；编辑于星期二\10点48分

TheflagellumofaGram-negativebacterium本文档共92页；当前第65页；编辑于星期二\10点48分Thefilamentofbacterialflagellaiscomposedofsubunitsofaproteincalled

flagellin.

Thebaseoftheflagellumisdifferentinstructurefromthatofthefilament.Thereisawiderregionatthebaseoftheflagellumcalledthe

hook.Thehookconsistsofasingletypeofproteinandfunctionstoconnectthefilamenttothemotorportionoftheflagellum.

The

basalbody

isanchoredinthecytoplasmicmembraneandcellwall.Thebasalbodyconsistsofasmallcentralrodthatpassesthroughasystemofrings.本文档共92页；当前第66页；编辑于星期二\10点48分Ingram-positiveBacteria,whichlacktheouterlipopolysaccharidelayer,onlytheinnerpairofringsispresent.SurroundingtheinnerringandanchoredinthecytoplasmicmembraneareapairofproteinscalledMot.Theseproteinsactuallydrivetheflagellarmotorcausingatorquethatrotatesthefilament.Afinalsetofproteins,calledtheFliproteinsfunctionasthemotorswitch,reversingrotationoftheflagellainresponsetointracellularsignals.Ingram-negativeBacteria,anouterringisanchoredinthelipopolysaccharidelayerandanotherinthepeptidoglycanlayerofthecellwall,andaninnerringislocatedwithinthecytoplasmicmembrane.本文档共92页；当前第67页；编辑于星期二\10点48分Themovementofaprocaryoticflagellumresultsfromrotationofitsbasalbodyandissimilartothemovementoftheshaftofanelectricmotor.Bacterialcellscanalterthespeedanddirectionofrotationofflagellaandthusarecapableofvariouspatternsofmotility.本文档共92页；当前第68页；编辑于星期二\10点48分Fimbriae

canbeevenlydistributedovertheentiresurfaceofthecell.Theycannumberanywherefromafewtoseveralhundredpercell.Fimbriaeallowacelltoadheretosurfacesincludingthesurfacesofothercells.

Piliareusuallylongerthanfimbriaeandnumberonlyoneortwopercell.PilifunctiontojoinbacterialcellspriortothetransferofDNAfromonecelltoanother.Fpilus本文档共92页；当前第69页；编辑于星期二\10点48分Manyprokaryotescontainacellsurfacelayercomposedofatwo-dimensionalarrayofprotein.TheselayersarecalledS-layers.S-layershavebeendetectedinrepresentativesofvirtuallyeveryphylogeneticgroupingofBacteriaandarenearlyuniversalamongArchaea.InsomespeciesofArchaeatheS-layerisalsothecellwall.ParacrystallineSurfaceLayers(S-Layers)本文档共92页；当前第70页；编辑于星期二\10点48分ThemajorfunctionofS-layersisunknown.Astheinterfacebetweenthecellanditsenvironment,itislikelythatincellsthatproducethemtheS-layeratleastfunctionsasanexternalpermeabilitybarrier,allowingthepassageoflow-molecular-weightsubstanceswhileexcludinglargemolecules.本文档共92页；当前第71页；编辑于星期二\10点48分2.7BacterialEndosporesCertainspeciesofbacteriaproducespecialstructurecalledendospores.Theyareveryresistanttoheatandcannotbedestroyedeasily,evenbyharshchemicals.Endosporesarealsoresistanttootherharmfulagentssuchasdrying,UVradiation,acidsandchemicaldisinfectants.本文档共92页；当前第72页；编辑于星期二\10点48分SporulatingcellCentralcoreCortexSporecoat/membraneexosporiumMicrographofaendosporeVegetativecell本文档共92页；当前第73页；编辑于星期二\10点48分本文档共92页；当前第74页；编辑于星期二\10点48分Manyprokaryoticorganismssecreteontheirsurfacesslimyorgummymaterials.Avarietyofthesestructuresconsistofpolysaccharide,andafewconsistofprotein.Thetermscapsuleandslimelayerarefrequentlyusedtodescribepolysaccharidelayers.Demonstrationofthepresenceofacapsuleisusuallybymeansofnegativestaining

CapsulesandSlimeLayers本文档共92页；当前第75页；编辑于星期二\10点48分LowpHvalue,andcontainssmallacid-solublesporeproteins(SASPs)StructureofDPA

PropertiesofEndosporeandItsResistanceContainingabundantDPA(dipicolinicacid)whichiscombinedwithcalciumions.Lowerwatercontent–only10-30%ofthewatercontentofthevegetativecell.本文档共92页；当前第76页；编辑于星期二\10点48分Sporulationinvolvesaverycomplexseriesofeventsincellulardifferentiation.Bacterialsporulationdoesnotoccurwhencellsaredividingexponentiallybutonlywhengrowthceasesowingtotheexhaustionofanessentialnutrient.Thus,cellsofBacillusceasevegetativegrowthandbeginsporulationwhenakeynutrientsuchasthecarbonornitrogensourcebecomeslimiting.EndosporeFormatiom本文档共92页；当前第77页；编辑于星期二\10点48分

Stagesinendosporeformation1.Axialfilamentformation2.Septumformatiom3.Engulfmentofforespore4.Cortexformation5.Coatsynthesis6.Completionofcoatsynthesis,Increaseinrefractilityandheatresistance7.Lysisofsporangium,sporeliberation本文档共92页；当前第78页；编辑于星期二\10点48分本文档共92页；当前第79页；编辑于星期二\10点48分1.Activation–

Usuallyresultsfromtreatmentslikeheating.2.Germination–

Breaksspore’sdormantstate.Thisprocessischaracterizedbysporeswelling,lossofresistancetoheatandotherstresses,lossofrefractilityandincreaseinmetabolicactivity.3.Outgrowth–

Thesporeprotoplastmakesnewcomponentsanddevelopsoncemoreintoanactivebacterium.SporeGermination本文档共92页；当前第80页；编辑于星期二\10点48分SeveralBacillusspecies,mostnotablyB.popilliaeandB.thuringiensis,produceintracellularcrystalsoftoxicglycoproteinswhentheysporulate.ToxiccrystalsParasporalCrystal(Spore-companionedcrystal)本文档共92页；当前第81页；编辑于星期二\10点48分2.8ComparisonofTheProkaryoticandEucaryoticCellPropertiesProkaryoteEukaryotePhylogeneticgroupsBacteria,ArchaeaEukarya:Algae,fungi,protozoa,plants,animalsSizeGenerallysmall,usually<2µmindiameterUsuallylarge,2to100µmindiameterNuclearmembranesAbsentPresentNucleolusAbsentPresentDNANotmitosisMitosis;mitoticapparatuswithmicrotubularspindle本文档共92页；当前第82页；编辑于星期二\10点48分PropertiesProkaryoteEukaryoteCytoplasmicmembraneUsuallylackssterols;hopanoidsmaybepresentSterolsusuallypresent;hopanoidsabsentRibosomes70sinsize80s,exceptforribosomesofmitochondriaandchloroplastswhichare70sMembranousorganellesAbsentSeveralpresentRespirationsystemPartofcytoplasmicmembrane;mitochondriaabsentInmitochondria;hydrogenosomesincertainanaerobicspeciesCellwallsPresent(inmost),composedofpeptidoglycan(bacteria),protein,otherpolysaccharides,glycoprotein(Archaea)Presentinplants,algae,fungi,usuallypolysaccharide;absentinanimals,mostprotozoa本文档共92页；当前第83页；编辑于星期二\10点48分TheirDNAisassociatedwithhistoneproteins.membrane-boundedorganelles9+2typeflagellaEucaryoticCell本文档共92页；当前第84页；编辑于星期二\10点48分Thechiefdistinguishingcharacteristicsofprocaryoticcellsare:1.Theirgeneticmaterial(DNA)isnotenclosedwithinamembrane.2.Theylackothermembrane-boundedorganelles.3.TheirDNAisnotassociatedwithhistoneproteins.4.Theircellwallsalmostalwayscontainthecomplexpolysaccharidepeptidoglycan.5. Theyusuallydividebybinaryfission.Duringthisprocess,theDNAiscopiedandthecellsplitsintotwocells.

本文档共92页；当前第85页；编辑于星期二\10点48分Summary1.Prokaryoticgeneticmaterialislocatedinanareacalledthenucleoidandisnotenclosedbyamembrane.2.Mostbacteriahaveacellwalloutsidetheplasmamembranetogivethemshapeandprotectthemfromosmoticlysis.Bacterialwallsarechemicallycomplexandusuallycontain

peptidoglycanormurein.本文档共92页；当前第86页；编辑于星期二\10点48分3.Bacteriaoftenareclassfiedaseithergrampositiveorgramnegativebasedondifferencesinc