微生物学英文课件3

Chapter3

TheProkaryotesChapterOutline3.1Bacteria3.2Actinomycetes3.3Cyanobacteria3.4Archaeobacteria

3.5Otherprokaryotes3.6ClassificationofbacteriaConceptsMicroorganismsaretoosmalltobeseenwithouttheuseofamicroscope.Thetechniques-suchassterilizationandtheuseofculturemediumarerequiredtoisolateandgrowthesemicrobes.Bacteriamaybespherical(cocci),rod-shaped(bacilli),spiral,orfilamentous.Mostbacteriacanbedividedintogram-positiveandgram-negativegroupsbasedontheircellwallstructureandresponsetotheGramstain.Bacteriasuchasmycoplasmaslackacellwall.Size,Shape,andArrangementofBacterialCellsTheyhaveafewbasicshapes-sphericalcoccus(plural,cocci,meaningberries),rod-shapedbacillus(plural,bacilli,meaninglittlestaffs),andspiral.Cm=10-2metermm=10-3meterμm=10-6meternm=10-9meter3.1BacteriaMostbacteriafallwithinarangefrom0.2to2.0μmindiameter

andfrom2to8μminlength.Morphology

(shape)Chemicalcomposition

(oftendetectedbystainingreactions)NutritionalrequirementsBiochemicalactivitiesSourceofenergy

(sunlightorchemicals)Howtoidentifyanunknownbacterialspecies?Factors:ArrangementofSphericalBacterialCellsTheMicrococcaceae

MicrococcusStaphylococcusStreptococcus

ThefamilyMicrococcaceae

containsgram-positivecocci,0.5-2.5μmindiameter,thatdivideinmorethanoneplanetoformregularorirregularclustersofcells.Allareaerobicorfacultativelyanaerobic.Thepeptidoglycan

di-aminoacidisL-lysine.Thethreemostimportantgeneraare:Micrococcus–aerobic,gram-positive,catalasepositive,cellarrangesmainlyinpairs,tetrads,orirregularclusters,nonmotile.Theyareoftenyellow,orangeorredincolorStaphylococcus-facultativelyanaerobic,gram-positive,usuallyformirregularclusters,nonmotile,catalasepositivebutoxidasenegative,fermentglucoseanaerobically.staphylococcistaphylococciStreptococcus-

facultativelyanaerobicormicroaerophilic,catalasenegative,gram-positive,Cellarrangesinpairsorchains,usuallynonmotile,

Afewspeciesareanaerobicratherthanfacultative.

Bacillidivideonlyacrosstheirshortaxis,sotherearefewergroupingsofbacillithanofcocci.

Rod-shapedbacteria

SinglebacillusDiplobacillistreptobacilliCoccobacillusClostridiumbotulinusC.butyricumC.aceticumC.tetaniC.putrificumBacillussubtilis,B.MycoidesB.PastturiiB.megateriumB.ThuringiensisB.AnthracisB.BotulinusB.cereusSpore-formingrodshapedbacteriaAlmostallSpore-formingbacteriaareGram+Clostridium–AnaerobicBacillus–AerobicNonspore-formingrodshapedbacteriaMostnonspore–formingrodshapedbacteriaareGram-Representatives:EscherchiacoliAlcaligenesProteusFlavobacteriaPseudomonasRhizobiumAzotobacterVibrio,SpirillumandSpirocheteSomebacteriaareshapedlikelongrodstwistedintospiralsorhelices;theyarecalledvibrios(likecommasorincompletespirals),spirillaifrigidandspirocheteswhenflexable.vibriospirillumspirochete

3.2ActinomycetesActinomycetesarefilamentousbacteria.Theirmorphologyresemblesthatofthefilamentousfungi;however,thefilamentsofactinomycetesconsistofprocaryoticcells.Someactinomycetesresemblemoldsbyformingexternallycarriedasexualsporesforreproduction.

Filamentous,HighG+Ccontent,Gram-positive(63–78%GC)ChainofconidiosporesAgarsurfaceSubstratemyceliumAerialhyphaeThecrosssectionofanactinomycetecolonyshowingthesubstratemyceliumandaerialmyceliumwithchainsofconidiosporesVarioustypesofspore-bearingstructuresonthestreptomycesRepresentivegenera:StreptomycesNocardiaActinomycesMicromonosporaStreptosporangiumActinoplanesFrankiaOver500distinctantibioticsubstanceshavebeenshowntobeproducedbystreptomycete.Mostantibioticsareefficientagainstdifferentbacteria.Morethan50antibioticshavebeenusedinhumanandveterinarymedicine,agricultureandindustryAntibioticsActinomycetesChainofconidiosporesAgarsurfaceSubstratemyceliumAerialhyphaeThecrosssectionofanactinomycetecolonyshowingthesubstratemyceliumandaerialmyceliumwithchainsofconidiosporesVarioustypesofspore-bearingstructuresonthestreptomyces

Streptomycesspores,calledconidia,arenotrelatedinanywaytotheendosporesofBacillusandClostridiumbecausethestreptomycetesporesareproducedsimplybytheformationofcross-wallsinthemultinucleatesporophoresfollowedbyseparationoftheindividualcellsdirectlyintospores.EcologyandisolationofStreptomyces:AlkalineandneutralsoilsaremorefavorableforthedevelopmentofStreptomycesthanareacidsoils.Streptomycesrequirealowerwaterpotentialforgrowththanmanyothersoilbacteria.MediaoftenselectiveforStreptomycescontaintheusualassortmentofinorganicsalts

Thestreptonycetesarealargegroupoffilamentous,grampositivebacteriathatformsporesattheendofaerialfilaments.TheyhavethehighestGCpercentageintheDNAbasecompositionofanybacteriaknown.ManyclinicallyimportantantibioticshavecomefromStreptomycetesspeciesConcept3.3CyanobacteriaThecyanobacteriahavetypicalprokaryoticcellstructuresandanormalgram-negativecellwall.Theyrangeindiameterfromabout1–10µmandmaybeunicellularorformfilaments.Theyhavechlorophyllandcarryoutoxygen-producingphotosynthesis,muchasplantsandtheeukaryoticalgaedo.

FilamentousCyanobacterium,

Anabaenasp.

(SEMx5,000)Nonfilamentous

cyanobacteriaThemorphologicaldiversityofthecyanobacteriaisconsiderable.Bothunicellularandfilamentousformsareknown,andconsiderablevariationwithinthesemorphologicaltypesoccurs.

Heterocystshaveintercellularconnectionswithadjacentvegetativecells,andthereismutualexchangeofmaterialsbetweenthesecells,withproductsofphotosynthesismovingfromvegetativecellstoheterocystsandproductsofnitrogenfixationmovingfromheterocyststovegetativecells.

PhotosynthesisNitrogenfixationMainfunctionofCyanobacteria

Thecyanobacteriaarethelargestandmostdiversegroupofphotosyntheticbacteria.Thestructureandphysiologyoftheheterocystensuresthatitwillremainanaerobic;itisdedicatedtonitrogenfixation.Itshouldbenotedthatnitrogenfixationalsoiscarriedoutbycyanobacteriathatlackheterocysts.

Cycnobacteriaarecapableofconsiderablemetabolicflexibility.Thenutritionofcyanobacteriaissimple.Vitaminsarenotrequired,andnitrateorammoniaisusedasnitrogensource.Nitrogen-fixingspeciesarecommon.Mostspeciestestedareobligatephototrophs,However,somecyanobacteriaareabletogrowinthedarkonorganiccompounds,usingtheorganicmaterialasbothcarbonandenergysource.

Physiologyofcyanobacteria:

Manycyanobacteriaproducepotentneurotoxins,andduringwaterbloomswhenmassiveaccumulationsofcyanobacteriamaydevelop,animalsingestingsuchwatermaysuccumbrapidly.Problems!3.4TheArchaebacteria

Althougharchaebacteriaareclassifiedasprocaryotes,thesecellsappeartobefundamentallydifferentfromtypicaIbacteriaorcyanobacteria.Infact,theyrepresentacelltypethatseemstobeneithereucaryoticnoreubacterial.

Theyareabout1micrometer(um)indiameter,thesizeoftypicalprocaryotes.Theylackmembrane-boundorganelles.Theyhavenuclearbodies(nucleoids)ratherthantrue,menbraneeboundnuclei.Theirribosomesare70S,thesizeofthosefoundintypicalprokaryotes.Thearchaebacteriahavethefollowinguniquecombinationoftraits:Prokaryotictraits:

Theircellwallscompletelylackpeptidoglycan.Theirproteinsynthesismachineryissensitivetoinhibitorsthattypicallyaffectonlyeukaryotesandisresistanttomanyinhibitorsthataffectprokaryotes.Someoftheirproteins,pigments,andbiochemicalprocessescloselyresemblethosefoundineukaryoticcells.Eukaryotictraits:Archaebacteriaincludethreegroups:1.Themethanogens,strictanaerobesthatproducemethane(CH4)fromcarbondioxideandhydrogen.2.Extremehalophiles,whichrequirehighconcentrationsofsaltforsurvival.3.Thermoacidophiles,whichnormallygrowinhot,acidicenvironments.MethanogenicbacteriaarestrictanaerobesthatobtainenergybyconvertingC02,H2,formate,acetate,andothercompoundstoeithermethaneormethaneandC02.C02+4H2CH4+2

H2OCH3C00HC02+CH4Methanogenesismayeventuallyserveasamajorsourceofpollution-freeenergy?!Sewagetreatmentplantsusethemethaneproducedtogenerateheatandelectricity.Theyaregram-negative,aerobic,irregularlylobedsphericalbacteriawithatemperatureoptimumaround70-800CandapHoptimumof2to3.Theircellwallcontainslipoproteinandcarbohydratesbutlackspeptidoglycan.ExtremelythermophilicbacteriaTheirmostdistinctivecharacteristicistheirrequirementofahighconcentrationofsodiumchlorideforgrowth.Theyareaerobicchemoheterotrophswithrespiratorymetabolismandrequirecomplexnutrients,usuallyproteinsandaminoacids,forgrowth.

Extremehalophilicbacteria3.5OtherprokaryotesRickettsia

ChlamydiaMycoplasma

Bdellovirio3.Manyspeciesofthemcausediseaseinhumansandotheranimals.Rickettsia1.0.2-0.5µmindiameter.obligateintracellularparasites.Themajorityofthemaregram-negativeandmultiplyonlywithinhostcells.

2.Binaryfissionwithinhostcells.TheylacktheenzymaticcapabilitytoproducesufficientamountsofATPtosupporttheirreproduction.TheyobtaintheATPfromhostcells.ChlamydiaObligateintracellularparasites,unabletogeneratesufficientATPtosupporttheirreproduction.Gram-negativeandcelldividesbybinaryfissionCausehuman

respiratoryandgenitourinarytractdisease,andinbirdstheycauserespiratorydisease.MycoplasmaDiameter=0.1-0.25µm.Theylackcellwall,areboundedbyasingletriple-layeredmembrane.Theyarethesmallestorganismscapableofself-reproduction.Severalofthemcausediseasesinhumans.(pneumonia,respiratorytractdisease)Thecolonyis“friedegg”appearance.Bdellovirio3.6Classificationofbacteria4.NUMERICALTAXONOMY1.MORPHOLOGICALCHARACTERISTICS2.DIFFERENTIALSTAINING3.NUCLEICACIDHYBRIDIZATIONProtistaProkaryotaeFive-kingdomsystemisacommonlyacceptedsystemofclassificationFungiPlantAnimalArchaebacteriaEubacteriaEukaryotesUniversalPhylogeneticTreederivedfromcomparativesequencingof16Sor18SRNA.Notethethree

majordomainsoflivingorganisms.DivisionsandClassesintheKingdomProcaryotae(Monera)IdentifiedbyCommonNamesDIVISION

CLASS

NonphotosyntheticbacteriaTypicalgram-negativecellwall

Anaerobicphotosyntheticbacteria

CyanobacteriaTypicalgram-positivecellwallWall-lessprocaryotesUnusualwallsRodsandcocci

ActionmycetesandrelatedorganismsMycopeanasArchaeobacteriaThetaxonomicclassificationschemeforbacteriamaybefoundinBergey'sManualofSystematicBacteriology.

In

Bergey'sManual,bacteriaaredividedintofourdivisions.Threedivisionsconsistofeubacterialcells,andthefourthdivisionconsistsofthearchaeobacteria.Eachdivisionisdividedintoclasses

Strainisagroupofcellsallderivedfromasinglecell.

ClassesaredividedintoordersfamiliesgeneraspeciesBacterialspecies

isdefinedsimplyasapopulationofcellswithsimilarcharacteristics.Morphologicalcharacteristicsareusefulinidentifyingbacteria.Forexample,differencesinsuchstructuresasendosporesorflagellacanbehelpful.However,manymicroorganismsappeartoosimilartobeclassifiedbytheirstructures.MORPHOLOGICALCHARACTERISTICS(ForexampleGramstaining)Mostbacteriaareeithergram-positiveorgram-negative.Butnotusefulinidentifyingeitherthewall-lessbacteriaorthearchaeobacteriawithunusualwalls.DIFFERENTIALSTAININGNUCLEICACIDHYBRI