Ch 27 supplement

Ch 27 supplement - CHAPTER27 BACTERIAANDARCHAEA

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Unformatted text preview: CHAPTER27 BACTERIAANDARCHAEA Overview:MastersofAdaptation  Itspinkcolorcomesfromlivingprokaryotes Figure27.1 Prokaryotesthrivealmosteverywhere,includingplacestooacidic,salty,cold,orhotformostotherorganisms Mostprokaryotesaremicroscopic,butwhattheylackinsizetheymakeupforinnumbers Therearemoreinahandfuloffertilesoilthanthenumberofpeoplewhohaveeverlived Prokaryotesaredividedintotwodomains:bacteriaandarchaea  Concept27.1:Structuralandfunctionaladaptationscontributetoprokaryoticsuccess  Mostprokaryotesareunicellular,althoughsomespeciesformcolonies Mostprokaryoticcellsare0.5 5µm,muchsmallerthanthe10 100µmofmanyeukaryoticcells Prokaryoticcellshaveavarietyofshapes Thethreemostcommonshapesarespheres(cocci),rods(bacilli),andspirals Figure27.2  Cell ­SurfaceStructures Animportantfeatureofnearlyallprokaryoticcellsistheircellwall,whichmaintainscellshape,protectsthecell, andpreventsitfromburstinginahypotonicenvironment Eukaryotecellwallsaremadeofcelluloseorchitin Bacterialcellwallscontainpeptidoglycan,anetworkofsugarpolymerscross ­linkedbypolypeptides Archaeacontainpolysaccharidesandproteinsbutlackpeptidoglycan ScientistsusetheGramstaintoclassifybacteriabycellwallcomposition Gram ­positivebacteriahavesimplerwallswithalargeamountofpeptidoglycan Gram ­negativebacteriahavelesspeptidoglycanandanoutermembranethatcanbetoxic Figure27.3 Manyantibioticstargetpeptidoglycananddamagebacterialcellwalls Gram ­negativebacteriaaremorelikelytobeantibioticresistant Apolysaccharideorproteinlayercalledacapsulecoversmanyprokaryotes Figure27.4 Someprokaryoteshavefimbriae,whichallowthemtosticktotheirsubstrateorotherindividualsinacolony Pili(orsexpili)arelongerthanfimbriaeandallowprokaryotestoexchangeDNA Figure27.5 Motility:TaxisandChemotaxis Inaheterogeneousenvironment,manybacteriaexhibittaxis,theabilitytomovetowardorawayfroma stimulus Chemotaxisisthemovementtowardorawayfromachemicalstimulus Motility:Flagella Mostmotilebacteriapropelthemselvesbyflagellascatteredaboutthesurfaceorconcentratedatoneorboth ends Flagellaofbacteria,archaea,andeukaryotesarecomposedofdifferentproteinsandlikelyevolved independently Figure27.6  Prokaryoticvs.EukaryoticFlagella Bacterialflagellaarecomposedofamotor,hook,andfilament  InternalOrganizationandDNA Prokaryoticcellsusuallylackcomplexcompartmentalization Someprokaryotesdohavespecializedmembranesthatperformmetabolicfunctions Theseareusuallyinfoldingsoftheplasmamembrane Figure27.7 TheprokaryoticgenomehaslessDNAthantheeukaryoticgenome Mostofthegenomeconsistsofacircularchromosome Thechromosomeisnotsurroundedbyamembrane;itislocatedinthenucleoidregion SomespeciesofbacteriaalsohavesmallerringsofDNAcalledplasmids Figure27.8 TherearesomedifferencesbetweenprokaryotesandeukaryotesinDNAreplication,transcription,and translation Theseallowpeopletousesomeantibioticstoinhibitbacterialgrowthwithoutharmingthemselves  ReproductionandAdaptation Prokaryotesreproducequicklybybinaryfissionandcandivideevery1 3hours Keyfeaturesofprokaryoticreproduction: Theyaresmall Theyreproducebybinaryfission Theyhaveshortgenerationtimes Manyprokaryotesformmetabolicallyinactiveendospores,whichcanremainviableinharshconditionsfor centuries Figure27.9  Concept27.2:Rapidreproduction,mutation,andgeneticrecombinationpromotegeneticdiversityinprokaryotes Prokaryoteshaveconsiderablegeneticvariation Threefactorscontributetothisgeneticdiversity: Rapidreproduction Mutation Geneticrecombination  RapidReproductionandMutation Prokaryotesreproducebybinaryfission,andoffspringcellsaregenerallyidentical Mutationratesduringbinaryfissionarelow,butbecauseofrapidreproduction,mutationscanaccumulate rapidlyinapopulation Highdiversityfrommutationsallowsforrapidevolution  GeneticRecombination Geneticrecombination,thecombiningofDNAfromtwosources,contributestodiversity ProkaryoticDNAfromdifferentindividualscanbebroughttogetherbytransformation,transduction,and conjugation Movementofgenesamongindividualsfromdifferentspeciesiscalledhorizontalgenetransfer TransformationandTransduction AprokaryoticcellcantakeupandincorporateforeignDNAfromthesurroundingenvironmentinaprocess calledtransformation Transductionisthemovementofgenesbetweenbacteriabybacteriophages(virusesthatinfectbacteria) Figure27.11 ­4  ConjugationandPlasmids Conjugationistheprocesswheregeneticmaterialistransferredbetweenprokaryoticcells Inbacteria,theDNAtransferisoneway Adonorcellattachestoarecipientbyapilus,pullsitcloser,andtransfersDNA ApieceofDNAcalledtheFfactorisrequiredfortheproductionofpili Figure27.12  TheFFactorasaPlasmid CellscontainingtheFplasmidfunctionasDNAdonorsduringconjugation CellswithouttheFfactorfunctionasDNArecipientsduringconjugation TheFfactoristransferableduringconjugation TheFFactorintheChromosome AcellwiththeFfactorbuiltintoitschromosomesfunctionsasadonorduringconjugation Therecipientbecomesarecombinantbacterium,withDNAfromtwodifferentcells Figure27.13b ­3  RPlasmidsandAntibioticResistance Rplasmidscarrygenesforantibioticresistance Antibioticskillsensitivebacteria,butnotbacteriawithspecificRplasmids Throughnaturalselection,thefractionofbacteriawithgenesforresistanceincreasesinapopulationexposedto antibiotics Antibiotic ­resistantstrainsofbacteriaarebecomingmorecommon  Concept27.3:Diversenutritionalandmetabolicadaptationshaveevolvedinprokaryotes Prokaryotescanbecategorizedbyhowtheyobtainenergyandcarbon Phototrophsobtainenergyfromlight Chemotrophsobtainenergyfromchemicals AutotrophsrequireCO2asacarbonsource Heterotrophsrequireanorganicnutrienttomakeorganiccompounds Energyandcarbonsourcesarecombinedtogivefourmajormodesofnutrition: Photoautotrophy Chemoautotrophy Photoheterotrophy Chemoheterotrophy Table27.1  TheRoleofOxygeninMetabolism ProkaryoticmetabolismvarieswithrespecttoO2 ObligateaerobesrequireO2forcellularrespiration ObligateanaerobesarepoisonedbyO2andusefermentationoranaerobicrespiration FacultativeanaerobescansurvivewithorwithoutO2  NitrogenMetabolism Nitrogenisessentialfortheproductionofaminoacidsandnucleicacids Prokaryotescanmetabolizenitrogeninavarietyofways Innitrogenfixation,someprokaryotesconvertatmosphericnitrogen(N2)toammonia(NH3) MetabolicCooperation Cooperationbetweenprokaryotesallowsthemtouseenvironmentalresourcestheycouldnotuseasindividual cells InthecyanobacteriumAnabaena,photosyntheticcellsandnitrogen ­fixingcellscalledheterocysts(or heterocytes)exchangemetabolicproducts Figure27.14 Insomeprokaryoticspecies,metaboliccooperationoccursinsurface ­coatingcoloniescalledbiofilms  Concept27.4:Molecularsystematicsisilluminatingprokaryoticphylogeny Untilthelate20thcentury,systematistsbasedprokaryotictaxonomyonphenotypiccriteria Applyingmolecularsystematicstotheinvestigationofprokaryoticphylogenyhasproduceddramaticresults LessonsfromMolecularSystematics Molecularsystematicsledtothesplittingofprokaryotesintobacteriaandarchaea Molecularsystematistscontinuetoworkonthephylogenyofprokaryotes Figure27.15 Theuseofpolymerasechainreaction(PCR)hasallowedformorerapidsequencingofprokaryotegenomes Ahandfulofsoilmaycontain10,000prokaryoticspecies Horizontalgenetransferbetweenprokaryotesobscurestherootofthetreeoflife  Archaea Archaeasharecertaintraitswithbacteriaandothertraitswitheukaryotes Figure27.UN01 Table27.2 Somearchaealiveinextremeenvironmentsandarecalledextremophiles Extremehalophilesliveinhighlysalineenvironments Extremethermophilesthriveinveryhotenvironments Figure27.16 Methanogensliveinswampsandmarshesandproducemethaneasawasteproduct MethanogensarestrictanaerobesandarepoisonedbyO2 Inrecentyears,geneticprospectinghasrevealedmanynewgroupsofarchaea SomeofthesemayoffercluestotheearlyevolutionoflifeonEarth  Bacteria Bacteriaincludethevastmajorityofprokaryotesofwhichmostpeopleareaware Diversenutritionaltypesarescatteredamongthemajorgroupsofbacteria Figure27.UN02  MajorGroupsofBacteria Proteobacteria Alpha Beta Gamma Delta Epsilon Chlamydias Spirochetes Cyanobacteria Gram+veBacteria  Proteobacteria Thesegram ­negativebacteriaincludephotoautotrophs,chemoautotrophs,andheterotrophs Someareanaerobic,andothersaerobic Figure27.17 ­a Figure27.17a  Subgroup:AlphaProteobacteria Manyspeciesarecloselyassociatedwitheukaryotichosts Scientistshypothesizethatmitochondriaevolvedfromaerobicalphaproteobacteriathroughendosymbiosis Example:Rhizobium,whichformsrootnodulesinlegumesandfixesatmosphericN2 Example:Agrobacterium,whichproducestumorsinplantsandisusedingeneticengineering Figure27.17b  Subgroup:BetaProteobacteria Example:thesoilbacteriumNitrosomonas,whichconvertsNH4+toNO2  Figure27.17c  Subgroup:GammaProteobacteria ExamplesincludesulfurbacteriasuchasChromatiumandpathogenssuchasLegionella,Salmonella,andVibrio cholerae Escherichiacoliresidesintheintestinesofmanymammalsandisnotnormallypathogenic Figure27.17d  Subgroup:DeltaProteobacteria Example:theslime ­secretingmyxobacteria Figure27.17e  Subgroup:EpsilonProteobacteria ThisgroupcontainsmanypathogensincludingCampylobacter,whichcausesbloodpoisoning,andHelicobacter pylori,whichcausesstomachulcers Figure27.17f Figure27.17 ­b  Chlamydias Thesebacteriaareparasitesthatlivewithinanimalcells Chlamydiatrachomatiscausesblindnessandnongonococcalurethritisbysexualtransmission Figure27.17g  Spirochetes Thesebacteriaarehelicalheterotrophs Someareparasites,includingTreponemapallidum,whichcausessyphilis,andBorreliaburgdorferi,whichcauses Lymedisease Figure27.17h  Cyanobacteria ThesearephotoautotrophsthatgenerateO2 Plantchloroplastslikelyevolvedfromcyanobacteriabytheprocessofendosymbiosis Figure27.17i  Gram ­PositiveBacteria Gram ­positivebacteriainclude Actinomycetes,whichdecomposesoil Bacillusanthracis,thecauseofanthrax Clostridiumbotulinum,thecauseofbotulism SomeStaphylococcusandStreptococcus,whichcanbepathogenic Mycoplasms,thesmallestknowncells Figure27.17j Figure27.17k  Concept27.5:Prokaryotesplaycrucialrolesinthebiosphere Prokaryotesaresoimportantthatiftheyweretodisappeartheprospectsforanyotherlifesurvivingwouldbe dim ChemicalRecycling Prokaryotesplayamajorroleintherecyclingofchemicalelementsbetweenthelivingandnonliving componentsofecosystems Chemoheterotrophicprokaryotesfunctionasdecomposers,breakingdowndeadorganismsandwasteproducts Prokaryotescansometimesincreasetheavailabilityofnitrogen,phosphorus,andpotassiumforplantgrowth Figure27.18 Figure27.18a   EcologicalInteractions Symbiosisisanecologicalrelationshipinwhichtwospeciesliveinclosecontact:alargerhostandsmaller symbiont Prokaryotesoftenformsymbioticrelationshipswithlargerorganisms Inmutualism,bothsymbioticorganismsbenefit Incommensalism,oneorganismbenefitswhileneitherharmingnorhelpingtheotherinanysignificantway Inparasitism,anorganismcalledaparasiteharmsbutdoesnotkillitshost Parasitesthatcausediseasearecalledpathogens Figure27.19 Theecologicalcommunitiesofhydrothermalventsdependonchemoautotropicbacteriaforenergy  Concept27.6:Prokaryoteshavebothbeneficialandharmfulimpactsonhumans Someprokaryotesarehumanpathogens,butothershavepositiveinteractionswithhumans MutualisticBacteria Humanintestinesarehometoabout500 1,000speciesofbacteria Manyofthesearemutalistsandbreakdownfoodthatisundigestedbyourintestines PathogenicBacteria Prokaryotescauseabouthalfofallhumandiseases Forexample,Lymediseaseiscausedbyabacteriumandcarriedbyticks Figure27.20 Figure27.20a Figure27.20b Figure27.20c Pathogenicprokaryotestypicallycausediseasebyreleasingexotoxinsorendotoxins Exotoxinsaresecretedandcausediseaseeveniftheprokaryotesthatproducethemarenotpresent Endotoxinsarereleasedonlywhenbacteriadieandtheircellwallsbreakdown Horizontalgenetransfercanspreadgenesassociatedwithvirulence Somepathogenicbacteriaarepotentialweaponsofbioterrorism  ProkaryotesinResearchandTechnology ExperimentsusingprokaryoteshaveledtoimportantadvancesinDNAtechnology Forexample,E.coliisusedingenecloning Forexample,Agrobacteriumtumefaciensisusedtoproducetransgenicplants Bacteriacannowbeusedtomakenaturalplastics Prokaryotesaretheprincipalagentsinbioremediation,theuseoforganismstoremovepollutantsfromthe environment Bacteriacanbeengineeredtoproducevitamins,antibiotics,andhormones Bacteriaarealsobeingengineeredtoproduceethanolfromwastebiomass  ...
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This note was uploaded on 12/04/2011 for the course BIO 200 taught by Professor Ejiofor during the Fall '11 term at TN State.

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