華中農(nóng)業(yè)大學微生物學第二章

Chapter2

CellBiology現(xiàn)在是1頁\一共有92頁\編輯于星期三

2.1Overviewofthestructureofmicrobialcells2.2Procaryoticcellwall2.3Cytoplasmicmembrane2.4Cellulargeneticinformation2.5Cytoplasmicmatrix–RibosomeandInclusions2.6Componentsexternaltothecellwall2.7Bacterialendospores2.8ComparisonoftheprokaryoticandeukaryoticcellChapterOutline現(xiàn)在是2頁\一共有92頁\編輯于星期三ConceptsProkaryotesaresmallandsimpleinstructurewhencomparedwitheukaryotes,yettheyoftenhavecharacteristicshapeandsize.

Prokaryoticgeneticmaterialislocatedinanareacalledthenucleoidandisnotenclosedbyamembrane.Theprokaryoticcellwallalmostalwayshaspeptidoglycanandischemicallyandmorphologicallycomplex.現(xiàn)在是3頁\一共有92頁\編輯于星期三AprocaryoticcellAeucaryoticcell2.1OverviewofCellStructure現(xiàn)在是4頁\一共有92頁\編輯于星期三3.TheircellwallalmostalwayscontainthecomplexpolysaccharidepeptidoglycanTheProkaryoticCell1.Theirgeneticmaterial(DNA)isnotenclosedwithinamembraneandtheylackothermembrane–boundedorganelles2.TheirDNAisnotassociatedwithhistidine4.Theyareverysmall!!現(xiàn)在是5頁\一共有92頁\編輯于星期三Schematicdiagramofabacterialcell現(xiàn)在是6頁\一共有92頁\編輯于星期三Size:

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

Acyanobacterium8x50um現(xiàn)在是7頁\一共有92頁\編輯于星期三sizecomparisonofmicroorganismsVisibility

scaleMeters

RelativesizeofMicrobesProkaryotesEukaryotesVirusesNakedeyeLightmicroscopeElectronmicroscope現(xiàn)在是8頁\一共有92頁\編輯于星期三acellincreasesinsize,itssurfacearea–to–volumeratiodecreasesSurfaceareaandvolumerelationshipsincells現(xiàn)在是9頁\一共有92頁\編輯于星期三spirallumShape:

Bacteriahaveafewbasicshapesspherical

coccusRod-shaped

bacillus現(xiàn)在是10頁\一共有92頁\編輯于星期三2.2ProkaryoticCellWallCellWall現(xiàn)在是11頁\一共有92頁\編輯于星期三Thecellwallofthebacterialcellisacomplex,semi-rigidstructurethatisresponsibleforthecharacteristicshapeofthecell.Thecellwallsurroundstheunderlying,fragileplasma(cytoplasmic)membraneandprotectsitandinternalpartsofthecellfromadversechangesinthesurroundingenvironment.Almostallprokaryoteshavecellwalls.現(xiàn)在是12頁\一共有92頁\編輯于星期三Gram+Gram-SchematicdiagramofbacterialcellwallsBacteriacanbedividedintotwomajorgroups,calledgram-positiveandgram-negative.Theoriginaldistinctionbetweengram-positiveandgram-negativewasbasedonaspecialstainingprocedure,theGramstain現(xiàn)在是13頁\一共有92頁\編輯于星期三TheGram-positivecellwallhasapeptidoglycanlayerthatisrelativelythick(ca.40nm)andcomprisesapproximately90%ofthecellwall.ThecellwallsofmostGram-positiveeubacteriaalsohaveteichoicacids.Gram-positiveCellWall現(xiàn)在是14頁\一共有92頁\編輯于星期三StructureoftheRepeatingUnitinPeptidoglycanTheseconstituentsareconnectedtoformarepeatingstructure,theglycantetrapeptide.Peptidoglycaniscomposedoftwosugarderivatives,N-acetylglucosamine(NAG)andN-acetylmuramicacid(NAM),andasmallgroupofaminoacidsconsistingofL-alanine,D-alanine,D-glutamicacid,andeitherlysineordiaminopimelicacid(DAP).現(xiàn)在是15頁\一共有92頁\編輯于星期三現(xiàn)在是16頁\一共有92頁\編輯于星期三Peptideandglycanunitsareconnectedinformationofthepeptidoglycansheet現(xiàn)在是17頁\一共有92頁\編輯于星期三Gram-positiveBacteriafrequentlyhaveacidicpolysaccharidescalledteichoicacidsattachedtotheircellwall.Thetermteichoicacidsincludesallwall,membrane,orcapsularpolymerscontainingglycerophosphateorribitolphosphateresidues.ThesepolyalcoholsareconnectedbyphosphateestersandusuallyhaveothersugarsandD-alanineattached.

TeichoicAcids現(xiàn)在是18頁\一共有92頁\編輯于星期三Teichoicacidsandlipoteichoicacidsarearrangedintheoverallwallstructureofgram-positiveBacteria.TeichoicacidLipoteichoicacid現(xiàn)在是19頁\一共有92頁\編輯于星期三TheGram-negativecellwallisathinlayerattachedtoanoutermembranevialipoproteins.Theoutermembranecontains

phospholipidonitsinnersurfaceand

lipopolysaccharide(LPS)

on

itsoutersurface.Thespacebetweentheoutermembraneandthe

cytoplasmicmembraneiscalledthe

periplasmicspace.Teichoic

acidsdonotoccurinGram-negativebacterialcellwalls..

現(xiàn)在是20頁\一共有92頁\編輯于星期三現(xiàn)在是21頁\一共有92頁\編輯于星期三OsidechainCorepolysaccharideLipidAChemicalStructureofLipopolysaccharide現(xiàn)在是22頁\一共有92頁\編輯于星期三MolecularModelofE.coliLipopolysaccharide現(xiàn)在是23頁\一共有92頁\編輯于星期三Thebondsbetweenthecarbohydratesinpseudopeptidoglycanare

β1-3insteadof'β1-4

asinpeptidoglycan.

CellWallsofArchaebacteriaThearchaebacteria

donotcontainpeptidoglycan

intheircellwallsasoccursineubacteria.N-acetylmuramicacidandD-aminoacids

arenotfound

inthecellwallsofarchaebacteria.(Differencesfromeubacteria)現(xiàn)在是24頁\一共有92頁\編輯于星期三Somearchaebacteriahavewallscomposedof

pseudopeptidoglycan,

whichresemblesthepeptidoglycanofeubacteriabut

containsN-acetyltalosaminuronicacid

insteadofN-acetylmuramicacidand

L.-aminoacids

insteadoftheD-aminoacidsineubacterialcellwalls.現(xiàn)在是25頁\一共有92頁\編輯于星期三ProtoplastFormation

Peptidoglycancanbedestroyedbycertainagentsforinstancelysozyme,thatbreaksthe1,4-glycosidicbondsbetweenN-acetylglucosamineandN-acetylmuramicacidinthemolecule.現(xiàn)在是26頁\一共有92頁\編輯于星期三Thedifferencebetweengram-positiveandgram-negativebacteriaisduetothephysicalnatureoftheircellwalls.Ifthecellwallisremovedfromgram-positivebacteria,theybecomegramnegative.

現(xiàn)在是27頁\一共有92頁\編輯于星期三Thepeptidoglycanseemstoactasapermeabilitybarrierpreventinglossofcrystalviolet.Gram-negativepeptidoglycanisverythin,notashighlycross-linked,andhaslargerpores.Alcoholtreatmentalsomayextractenoughlipidfromthegramnegativewalltofurtherincreaseitsporosity.Forthesereasons,alcoholmorereadilyremovesthepurplecrystalviolet-iodinecomplexfromgram-negativebacteria.TheMechanismofGramStaining現(xiàn)在是28頁\一共有92頁\編輯于星期三

ProceduresofGramStaining現(xiàn)在是29頁\一共有92頁\編輯于星期三GrampositiveorGramnegative?現(xiàn)在是30頁\一共有92頁\編輯于星期三現(xiàn)在是31頁\一共有92頁\編輯于星期三Structureofcytoplasmicmembrane2.3CytoplasmicMembraneFunctionofcytoplasmicmembraneMembrane現(xiàn)在是32頁\一共有92頁\編輯于星期三B.

Colorizedelectronmicrographof'thecytoplasmicmembrane(CM)ofthebacteriumBacillussubtilis

revealsthecharacteristicrailroadtrackappearanceofthislipidbilayer.

StructureofCytoplasmicMembraneItisatypicalUNITMEMBRANE!A.

Thetypicalcytoplasmicmembraneofprokaryoticandeukaryoticcellsisalipidbilayer,asillustratedhereshowingtheorientationsofthehydrophilic(tanspheres)andhydrophobic(black)endsofphospholipidsthatmakeupthisstructure.現(xiàn)在是33頁\一共有92頁\編輯于星期三Thecytoplasmicmembrane,ahighlyselectivebarrier,isconstructedprincipallyoflipid,withinwhichcertainproteinsareembedded.Membranescontainboth

lipidsandproteins,althoughtheexactproportionsoflipidandproteinvarywidely.現(xiàn)在是34頁\一共有92頁\編輯于星期三Diagramofthestructureofcytoplasmicmembrane現(xiàn)在是35頁\一共有92頁\編輯于星期三3.Energyconservation-siteofgenerationanduseoftheprotonmotiveforce.

FunctionofMembrane1.Permeabilitybarrier

-preventsleakageandfunctionasgatewayfortransportofnutrientsintoandoutofthecell.2.Proteinanchor-siteofmanyproteinsinvolvedintransport,bioenergetics,andchemotaxis.現(xiàn)在是36頁\一共有92頁\編輯于星期三

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

現(xiàn)在是37頁\一共有92頁\編輯于星期三IntracellularMembraneSystemBacteriacellsdon’tcontainmembrane-enclosedorganelles.However,bacteriamayhavespecializedinvaginationsofthecytoplasmicmembrane.Theirfunctionmaybetoprovidealargermembranesurfaceforgreatermetabolicactivity.現(xiàn)在是38頁\一共有92頁\編輯于星期三StructureofMesosomeMesosomemaybeinvolvedin

wallformation

duringdivisionorplayarolein

chromosomereplication

anddistributiontodaughtercells.Itmayalsobeinvolvedin

secretoryprocesses現(xiàn)在是39頁\一共有92頁\編輯于星期三2.4CellularGeneticInformationNucleoid現(xiàn)在是40頁\一共有92頁\編輯于星期三BacterialChromosomeSupercoilingandchromosomestructureChromosomalcopynumber2.Plasmids現(xiàn)在是41頁\一共有92頁\編輯于星期三Micrographofabacteriumshowingthenucleoidregion(green)withinthecytoplasmwherethebacterialchromosomeoccurs現(xiàn)在是42頁\一共有92頁\編輯于星期三ThebacterialchromosomeisacircularDNAmacromoleculeexcept

inStreptomyces

whereitislinearand

Rhodobacter

sphaffoides,whichhastwoseparatechromosomes.

BacterialChromosomeThebacterialchromosomeisusuallya

singlecovalentlyclosedcircular

molecule.Theterm

nucleoidisusedtodescribeaggregatedDNAintheprokaryoticcell.現(xiàn)在是43頁\一共有92頁\編輯于星期三Rangeofgenomesizesinvirousgroupsoforganismsandtheorganellesofeukarya現(xiàn)在是44頁\一共有92頁\編輯于星期三Thebacterialchromosomeandsupercoiling:現(xiàn)在是45頁\一共有92頁\編輯于星期三ExampleofE.colicellThereareover

50supercoileddomain

intheE.colichromosome.ThetotalamountofDNAisabout

4600kb.IfthetotalDNAisopenedandlinearized,itwouldbe

1mminlength.Thethecellisonly

about2-3umlong.

SotopackagethismuchDNAintothecellrequiresthat

theDNAbehighlysupercoiled.現(xiàn)在是46頁\一共有92頁\編輯于星期三ElectronmicrographofanisolatednucleoidreleasedfromE.coli.

現(xiàn)在是47頁\一共有92頁\編輯于星期三Chromosomecopynumber

Bacteriathatreproduceasexuallyaretypically

haploid

ingeneticcomplement.Rapidlygrowingcellscontain

morethan

1copy

ofthechromosome,andonlywhencellgrowthhasceaseddoesthechromosomenumberapproachonepercell.現(xiàn)在是48頁\一共有92頁\編輯于星期三

Reproductionofabacterialcellrequiresthereplicationofthebacterialchromosome.ThemicrographshowsthesequenceofsynthesisofnewcircularloopsofdoublehelicalDNA.Bacterianormallyreproducebybinaryfission.Theinwardgrowthoftheseptumdividestheparentcelltoproducetwoequal-sizedprogenycells.現(xiàn)在是49頁\一共有92頁\編輯于星期三Plasmidsdon’tcontainthegeneticinformationfortheessentialmetabolicactivitiesofthecell,buttheygenerallydocontaingeneticinformationforspecialfeatures.

PlasmidProkaryoticcellshavesmallextra-chromosomal

geneticelementscalled

plasmids.現(xiàn)在是50頁\一共有92頁\編輯于星期三ResistantplasmidsColplasmidsConjugativeplasmidsMetabolicplasmids

MajorTypesofPlasmids現(xiàn)在是51頁\一共有92頁\編輯于星期三2.5CytoplasmicMatrixRibosomeandInclusionsRibosomeCarbonstoragepolymers–PHBandglycogenPhosphatepolymersSulfurGranulesGasVacuoles現(xiàn)在是52頁\一共有92頁\編輯于星期三Alleucaryoticandprocaryoticcellscontainribosomes,whichfunctionasthesitesofproteinsynthesis.Ribosomesarecomposedoftwosubunits

Procaryoticribosomesarecalled70Sribosomes,andthoseofeucaryoticcellsareknownas80Sribosomes

RibosomesTheletterSreferstoSvedbergunits,whichindicatetherelativerateofsedimentationduringultra-high-speedcentrifugation現(xiàn)在是53頁\一共有92頁\編輯于星期三現(xiàn)在是54頁\一共有92頁\編輯于星期三

Withinthecytoplasmofprocaryotic(andeucaryotic)cellsareseveralkindsofreservedeposits,knownasinclusions.Someinclusionsarecommontoawidevarietyofbacteria,whereasothersarelimitedtoasmallnumberofspeciesandthereforeserveasabasisforidentification.Amongthemoreprominentbacterialinclusionsarethefollowing:InclusionCarbonstoragepolymers–PHBandglycogenPhosphatepolymersSulfurGranulesGasVacuoles現(xiàn)在是55頁\一共有92頁\編輯于星期三Polyhydroxybutyricacid(PHB)PHBisa

lipidlikecompound

-oneofthemostcommoninclusionbodiesinprokaryoticorganisms.PHBiscommonlyfoundasastoragematerialand

uniquetobacteria

Glycogenisa

starchlikepolymer

ofglucosesubunits.GlycogengranulesareusuallysmallerthanPHBgranules.AVibriospecies現(xiàn)在是56頁\一共有92頁\編輯于星期三Manymicroorganismsaccumulategranulesofpolyphosphate,whicharelargereservesof

inorganicphosphates

thatcanbeusedinthesynthesisofATPPolyphosphategranule

inabacterialcellAPseudomonasspecies現(xiàn)在是57頁\一共有92頁\編輯于星期三ThesulfurglobulesinsidethecellsofpurplesulfurbacteriumChromatiumbuderiSomebacteria,includingmanyphotosyntheticbacteria,accumulate

elementalsulfurgranules

asaresultoftheirmetabolism.現(xiàn)在是58頁\一共有92頁\編輯于星期三Gasvacuoles(blue)andstoragegranules(red)inthecyanobacteriumMicrocystisTheformationofgasvacuolesbyaquaticbacteriaprovidesamechanismforadjustingthebuoyancyofthecell.Manyaquaticcyanobacteriausetheirgasvacuolestomoveupanddowninthewatercolumn.現(xiàn)在是59頁\一共有92頁\編輯于星期三2.6ComponentsexternaltothecellwallFlagellaFimbriaeandpiliCapsulesandslimelayers現(xiàn)在是60頁\一共有92頁\編輯于星期三Motilityallowsthecelltoreachdifferentregionsofitsenvironment.Inthestruggleforsurvival,movementtoanewlocationmaymeanthedifferencebetweensurvivalanddeathofthecell.But,asinanyphysicalprocess,cellmovementiscloselytiedtoanenergyexpenditure,andthemovementofflagellaisnoexception.

Manyprokaryotesaremotile,andthisabilitytomoveindependentlyisusually

duetoaspecialstructure,

the

flagellum

(plural,flagella).

現(xiàn)在是61頁\一共有92頁\編輯于星期三現(xiàn)在是62頁\一共有92頁\編輯于星期三Fourbasictypesofflagellararrangementsa.monotrichousb.amphitrichousc.

lophotrichousd.peritrichous現(xiàn)在是63頁\一共有92頁\編輯于星期三Flagellaarearrangeddifferentlyondifferentbacteria.Inpolarflagellationtheflagellaareattachedatoneorbothendsofthecell.Occasionallyatuft(group)offlagellamayariseatoneendofthecell,anarrangementcalledlophotrichous.Inperitrichousflagellationtheflagellaareinsertedatmanyplacesaroundthecellsurface(perimeans"around").Thetypeofflagellation,polarorperitrichous,isoftenusedasacharacteristicintheclassificationofbacteria.現(xiàn)在是64頁\一共有92頁\編輯于星期三

TheflagellumofaGram-negativebacterium現(xiàn)在是65頁\一共有92頁\編輯于星期三Thefilamentofbacterialflagellaiscomposedofsubunitsofaproteincalled

flagellin.

Thebaseoftheflagellumisdifferentinstructurefromthatofthefilament.Thereisawiderregionatthebaseoftheflagellumcalledthe

hook.Thehookconsistsofasingletypeofproteinandfunctionstoconnectthefilamenttothemotorportionoftheflagellum.

The

basalbody

isanchoredinthecytoplasmicmembraneandcellwall.Thebasalbodyconsistsofasmallcentralrodthatpassesthroughasystemofrings.現(xiàn)在是66頁\一共有92頁\編輯于星期三Ingram-positiveBacteria,whichlacktheouterlipopolysaccharidelayer,onlytheinnerpairofringsispresent.SurroundingtheinnerringandanchoredinthecytoplasmicmembraneareapairofproteinscalledMot.Theseproteinsactuallydrivetheflagellarmotorcausingatorquethatrotatesthefilament.Afinalsetofproteins,calledtheFliproteinsfunctionasthemotorswitch,reversingrotationoftheflagellainresponsetointracellularsignals.Ingram-negativeBacteria,anouterringisanchoredinthelipopolysaccharidelayerandanotherinthepeptidoglycanlayerofthecellwall,andaninnerringislocatedwithinthecytoplasmicmembrane.現(xiàn)在是67頁\一共有92頁\編輯于星期三Themovementofaprocaryoticflagellumresultsfromrotationofitsbasalbodyandissimilartothemovementoftheshaftofanelectricmotor.Bacterialcellscanalterthespeedanddirectionofrotationofflagellaandthusarecapableofvariouspatternsofmotility.現(xiàn)在是68頁\一共有92頁\編輯于星期三Fimbriae

canbeevenlydistributedovertheentiresurfaceofthecell.Theycannumberanywherefromafewtoseveralhundredpercell.Fimbriaeallowacelltoadheretosurfacesincludingthesurfacesofothercells.

Piliareusuallylongerthanfimbriaeandnumberonlyoneortwopercell.PilifunctiontojoinbacterialcellspriortothetransferofDNAfromonecelltoanother.Fpilus現(xiàn)在是69頁\一共有92頁\編輯于星期三Manyprokaryotescontainacellsurfacelayercomposedofatwo-dimensionalarrayofprotein.TheselayersarecalledS-layers.S-layershavebeendetectedinrepresentativesofvirtuallyeveryphylogeneticgroupingofBacteriaandarenearlyuniversalamongArchaea.InsomespeciesofArchaeatheS-layerisalsothecellwall.ParacrystallineSurfaceLayers(S-Layers)現(xiàn)在是70頁\一共有92頁\編輯于星期三ThemajorfunctionofS-layersisunknown.Astheinterfacebetweenthecellanditsenvironment,itislikelythatincellsthatproducethemtheS-layeratleastfunctionsasanexternalpermeabilitybarrier,allowingthepassageoflow-molecular-weightsubstanceswhileexcludinglargemolecules.現(xiàn)在是71頁\一共有92頁\編輯于星期三2.7BacterialEndosporesCertainspeciesofbacteriaproducespecialstructurecalledendospores.Theyareveryresistanttoheatandcannotbedestroyedeasily,evenbyharshchemicals.Endosporesarealsoresistanttootherharmfulagentssuchasdrying,UVradiation,acidsandchemicaldisinfectants.現(xiàn)在是72頁\一共有92頁\編輯于星期三SporulatingcellCentralcoreCortexSporecoat/membraneexosporiumMicrographofaendosporeVegetativecell現(xiàn)在是73頁\一共有92頁\編輯于星期三現(xiàn)在是74頁\一共有92頁\編輯于星期三Manyprokaryoticorganismssecreteontheirsurfacesslimyorgummymaterials.Avarietyofthesestructuresconsistofpolysaccharide,andafewconsistofprotein.Thetermscapsuleandslimelayerarefrequentlyusedtodescribepolysaccharidelayers.Demonstrationofthepresenceofacapsuleisusuallybymeansofnegativestaining

CapsulesandSlimeLayers現(xiàn)在是75頁\一共有92頁\編輯于星期三LowpHvalue,andcontainssmallacid-solublesporeproteins(SASPs)StructureofDPA

PropertiesofEndosporeandItsResistanceContainingabundantDPA(dipicolinicacid)whichiscombinedwithcalciumions.Lowerwatercontent–only10-30%ofthewatercontentofthevegetativecell.現(xiàn)在是76頁\一共有92頁\編輯于星期三Sporulationinvolvesaverycomplexseriesofeventsincellulardifferentiation.Bacterialsporulationdoesnotoccurwhencellsaredividingexponentiallybutonlywhengrowthceasesowingtotheexhaustionofanessentialnutrient.Thus,cellsofBacillusceasevegetativegrowthandbeginsporulationwhenakeynutrientsuchasthecarbonornitrogensourcebecomeslimiting.EndosporeFormatiom現(xiàn)在是77頁\一共有92頁\編輯于星期三

Stagesinendosporeformation1.Axialfilamentformation2.Septumformatiom3.Engulfmentofforespore4.Cortexformation5.Coatsynthesis6.Completionofcoatsynthesis,Increaseinrefractilityandheatresistance7.Lysisofsporangium,sporeliberation現(xiàn)在是78頁\一共有92頁\編輯于星期三現(xiàn)在是79頁\一共有92頁\編輯于星期三1.Activation–

Usuallyresultsfromtreatmentslikeheating.2.Germination–

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

Thesporeprotoplastmakesnewcomponentsanddevelopsoncemoreintoanactivebacterium.SporeGermination現(xiàn)在是80頁\一共有92頁\編輯于星期三SeveralBacillusspecies,mostnotablyB.popilliaeandB.thuringiensis,produceintracellularcrystalsoftoxicglycoproteinswhentheysporulate.ToxiccrystalsParasporalCrystal(Spore-companionedcrystal)現(xiàn)在是81頁\一共有92頁\編輯于星期三2.8ComparisonofTheProkaryoticandEucaryoticCellPropertiesProkaryoteEukaryotePhylogeneticgroupsBacteria,ArchaeaEukarya:Algae,fungi,protozoa,plants,animalsSizeGenerallysmall,usually<2μmindiameterUsuallylarge,2to100μmindiameterNuclearmembranesAbsentPresentNucleolusAbsentPresentDNANotmitosisMitosis;mitoticapparatuswithmicrotubularspindle現(xiàn)在是82頁\一共有92頁\編輯于星期三PropertiesProkaryoteEukaryoteCytoplasmicmembraneUsuallylackssterols;hopanoidsmaybepresentSterolsusuallypresent;hopanoidsabsentRibosomes70sinsize80s,exceptforribosomesofmitochondriaandchloroplastswhichare70sMembranousorganellesAbsentSeveralpresentRespirationsystemPartofcytoplasmicmembrane;mitochondriaabsentInmitochondria;hydrogenosomesincertainanaerobicspeciesCellwallsPresent(inmost),composedofpeptidoglycan(bacteria),protein,otherpolysaccharides,glycoprotein(Archaea)Presentinplants,algae,fungi,usuallypolysaccharide;absentinanimals,mostprotozoa現(xiàn)在是83頁\一共有92頁\編輯于星期三TheirDNAisassociatedwithhistoneproteins.membrane-boundedorganelles9+2typeflagellaEucaryoticCell現(xiàn)在是84頁\一共有92頁\編輯于星期三Thechiefdistinguishingcharacteristicsofprocaryoticcellsare:1.Theirgeneticmaterial(DNA)isnotenclosedwithinamembrane.2.Theylackothermembrane-boundedorganelles.3.TheirDNAisnotassociatedwithhistoneproteins.4.Theircellwallsalmostalwayscontainthecomplexpolysaccharidepeptidoglycan.5. Theyusuallydividebybinaryfission.Duringthisprocess,theDNAiscopiedandthecellsplitsintotwocells.

現(xiàn)在是85頁\一共有92頁\編輯于星期三Summary1.Prokaryoticgeneticmaterialislocatedinanareacalledthenucleoidandisnotenclosedbyamembrane.2.Mostbacteriahaveacellwalloutsidetheplasmamembranetogivethemshapeandprotectthemfromosmoticlysis.Bacterialwallsarechemicallycomplexandusuallycontain

peptidoglycanormurein.現(xiàn)在是86頁\一共有92頁\編輯于星期三3.Bacteriaoftenareclassfiedaseithergrampositiveorgramnegativebasedondifferencesincellwallstructureandthe