,ACCESSgTestgBankgforgBrockgBiologygofgMicroorganismsg16thgEditiongMadi
gan
CHAPTER
The Microbial World
g g
1
Summary
Chapterg1gintroducesgthegstudygofgmicrobiologygforgstudents,gmostgofgwhomgwillg
haveghadglittlegorgnogexposuregtogthegsubject.gConsequently,gyoughavegaggoodgopp
ortunitygtogprovidegangoverviewgofgmicrobiologygthatgdemonstratesgthegimportantg
rolesgmicroorganismsg(orgmicrobes)gplayginghumangactivitiesgandgingthegecologygo
fgthegentiregbiosphere.gThegabilitygofgmicroorganismsgtogexistgindependentlygingna
turegasgfree-
livinggcellsgwithinglargergmicrobialgcommunitiesg(Figureg1.1)gconfersgenormousga
daptivegadvantagesgovergcellsgofgmacroorganisms,gwhichgaregincapablegofganginde
pendentgexistence.
1.1 |gMicroorganisms,gTinygTitansgofgthegEarth
Describegtogstudentsgwaysgingwhichgmicrobiologygservesgasgbothgagbasicgandgangappliedgbi
ologicalgscience.gFromgagbasicgperspective,gthegstudygofgmicroorganismsginglaboratorygcult
ureghasgbeengthegprimarygmeansgbygwhichgthegfundamentalggeneticgandgbiochemicalgprope
rtiesgofglivinggcellsghavegbeengrevealed.gFromgangappliedgperspective,gmicroorganismsgdire
ctlygaffectgthegqualitygofghumanglifegingbothgdetrimentalgandgbeneficialgways.gAlthoughgmi
croorganismsgaregthegcausativegagentsgofgsomegofgthegmostgimportantghuman,ganimal,gandg
plantgdiseases,gtheygaregalsogusedgforgthegindustrialgproductiongofgantibiotics,gpharmaceutic
als,gandgfoods.gMicrobesgaregalsogincreasinglygbeinggusedgforgbeneficialgpurposesgasgdivers
egasgbioremediationgofgpollutedgsites,ggenegtherapiesgforggeneticgdiseases,gandgthegproducti
ongofgbiofuels.gMicrobiologygisgthereforegagsciencegofgfar-
reachinggscope,gwithgapplicationsgthatgaffectgthegqualitygofghumanglifegingagvarietygofgways
g(Figureg1.2).
Yougshouldgalsogemphasizegtogstudentsgthegimportancegofgmicroorganismsgingthegemerg
encegandgmaintenancegofghighergformsgofglife.gFromgthegproductiongofgmoleculargoxygeng(
bygcyanobacteria)gtogthegbiogeochemicalgcyclinggofgkeygelements,gsuchgasgcarbon,gnitrogen
,gandgsulfur,gmicroorganismsgplaygagmajorgrolegingsustaininggallglifegongthegplanet.gPointgo
utgingyourgcoursegintroductiongthatgforgallgthegreasonsgsummarizedgingthisgsection,gmicrobi
ologygisgthegfoundationgofgallgbiologicalgsciences.
1.2 |gStructuregandgActivitiesgofgMicrobialgCells
Becausegmicroorganismsggenerallygexistgasgfree-
livinggcells,gitgisgimportantgtogdiscussgthegcharacteristicsgofgcellsginggeneral.gEmphasizegthatgallgce
llsgexhibitgagnonrandomgorganizationgwithgagsemipermeablegmembranegboundarygthatgencompass
esganginternalgsystemgthatgisgnotgingequilibriumgwithgitsgenvironment.gPointgoutgthatgprokaryoticgc
ellsg(i.e.,gallgBacteriagandgArchaea)gdognotgcontaingmembrane-
bound,ginternalgorganellesgasgtraditionallygdescribedgforgeukaryoticgcellsg(thegEukarya;gFigureg1.4
mynursytest.store
,ACCESSgTestgBankgforgBrockgBiologygofgMicroorganismsg16thgEditiongMadi
gan
).gIngparticular,gthegorganizationgofgprokaryoticgDNAgasgagsinglegchromosomegingan
Copyrightg©g2021gPearsongEducation,gInc. CHAPTERg1gThegMicrobialgWorld 1
mynursytest.store
, ACCESSgTestgBankgforgBrockgBiologygofgMicroorganismsg16thgEditiongMadi
gan
arrangementgcalledgagnucleoid,gangaggregatedgmassgofggeneticgmaterialgwithingthegcytoplasm,gisging
starkgcontrastgtogthegcompartmentalized,gmultichromosomalgconfigurationgtypicallygfoundgingeukar
yotes.gHowever,gdespitegthegstructuralgandgmorphologicalgsimilaritiesgofgBacteriagandgArchaea,gma
kegsuregyourgstudentsgaregawaregearlygongthatgtheseggroupsgofgmicroorganismsghavegquitegdistinctge
volutionaryglineagesgandgare,gtherefore,gnotgcloselygrelatedgongaggeneticglevel.gThisgconceptgisgdisc
ussedgingmoregdetailgingSectiong1.5.
Thegabilitygofgcellsgtogmaintaingagthermodynamicgenergygflowgfargfromgequilibriumgd
efinesgwhatgwegrefergtogasgaglivinggsystem.gAllglivinggsystemsgdisplaygsomegformgofgenz
yme-drivengmetabolismgingwhichgbothgenergy-yieldingg(catabolic)gandgenergy-
gconsumingg(anabolic)gbiochemicalgreactionsgaregcatalyzedgconcurrently.gThesegchemica
lgtransformationsgallowgforgbiosynthesisgofgnewgcellgstructuresgand,gultimately,gcellgdivis
iong(microbialggrowth).gFigureg1.5gshowsgthegcharacteristicsgthatgdefinegcellularglife,gso
megofgwhichgareguniversalg(e.g.,gmetabolismgandgevolution)gandgsomegofgwhichgoccurgo
nlygingsomegcellsg(e.g.,gdifferentiationgandgmotility).
1.3 |gCellgSizegandgMorphology
Thegpresentationgingthegtextgofgthegsignificancegofgbeinggsmallgisgangimportantgconceptgforgstuden
tsgtoginternalizegasgtheygbegingtheirgstudygofgmicrobiology.gTableg1.1gshowsgthegwidegsizegrangeg
variabilitygofgbacterialgcells,gwhichgrangegfromgagdiametergofgaboutg0.2gµmgtogoverg700gµm.gUseg
thegtwogexamplesgofgunusuallyglargegbacteriagdiscussedgingthisgsectiongtogillustrategthegcurrentgup
perglimitgofgbacterialgcellgsize:g(1)gthegsurgeonfishggutgsymbiontgEpulopisciumgfishelsonig(>600gµ
mginglength;gFigureg1.6a),gandg(2)gthegsulfurgchemolithotrophgThiomargaritagnamibiensisg(750gµ
m;gFigureg1.6b).gThegevolutionaryg“rationale”gforgthegexistencegofgunusuallyglarge-
celledgbacteriagisgagmysterygwhengonegconsidersgthatgthegmetabolicgrategofgagcellgvariesginverselyg
withgthegsquaregofgitsgsize.gAskgyourgstudentsgforgideasgand/orghypothesesgthatgmightgexplaingtheg
selectivegadvantagegofglargegcellgsizegingthesegtwogprokaryotes.
Thegfactgthatgbacteriagcanglivegindependentlygasgsinglegcellsg(unlikegangindividualgcellgofgagmult
icellulargorganism)gsuggestsgthatgtheygmustgpossessgsomegcapabilitiesgthatgprovidegagselectivegadva
ntagegovergtheirgmulticellulargcounterpartsgthatgensuregtheirgsurvivalgongthegplanet.gSmallgcellsghave
gmoregsurfacegareagtogvolumeg(i.e.,gaghighergsurface-to-
volumegratio),gandgthisgalonegconfersgmanygofgthegevolutionarygadvantagesgofgbeinggsmall,gincludi
nggthegfollowing:
● Rapidgnutrientgandgwastegtransportgintogandgoutgofgthegcellgallowsgforgfastergmetabolicgratesga
ndggrowthgrates.
● Rapidggrowthgratesgresultgingthegrapidgproductiongofglargegpopulationsgofgcells.gThesegpopula
tions,gingturn,gcanggreatlygaffectgthegphysiochemicalgconditionsgofgangecosystemgwithingagsho
rtgtimegperiod.
● Transportgratesgaregagfunctiongofgthegsurfacegareagofgthegcytoplasmicgmembranegrelativegtogcell
gvolume.gUsegFigureg1.7gtogmathematicallygdemonstrategtogstudentsgthatgthegsurfacegareagofgag
spheregisgagfunctiongofgthegsquaregofgthegradius,gwhereasgthegvolumegofgagspheregisgagfunctiongofg
thegcubegofgthegradius.gThisgmeansgthatgthegsurface-to-
volumegratiogofgagsphericalgcellgcangbegexpressedgasg3/r,gwheregrgequalsgthegradiusgofgthegcell.g
Therefore,gagcoccusgcellghavinggagsmallergradiusghasgmoregsurfacegareagpergvolumegand,gthus,g
moregefficientgtransportgcapabilities,gthangagcoccusgcellghavinggaglargergradius.
● Ratesgofgevolutionarygchangegareghighergingsmaller,gfasterggrowingghaploidgcellsgthanginglarger,
2 INSTRUCTOR'SgMANUALgFORgBROCKgBIOLOGYgOFgMICROORGANISMS,g16e Copyrightg©g2021gPearsongEducation,gInc.
mynursytest.store
gan
CHAPTER
The Microbial World
g g
1
Summary
Chapterg1gintroducesgthegstudygofgmicrobiologygforgstudents,gmostgofgwhomgwillg
haveghadglittlegorgnogexposuregtogthegsubject.gConsequently,gyoughavegaggoodgopp
ortunitygtogprovidegangoverviewgofgmicrobiologygthatgdemonstratesgthegimportantg
rolesgmicroorganismsg(orgmicrobes)gplayginghumangactivitiesgandgingthegecologygo
fgthegentiregbiosphere.gThegabilitygofgmicroorganismsgtogexistgindependentlygingna
turegasgfree-
livinggcellsgwithinglargergmicrobialgcommunitiesg(Figureg1.1)gconfersgenormousga
daptivegadvantagesgovergcellsgofgmacroorganisms,gwhichgaregincapablegofganginde
pendentgexistence.
1.1 |gMicroorganisms,gTinygTitansgofgthegEarth
Describegtogstudentsgwaysgingwhichgmicrobiologygservesgasgbothgagbasicgandgangappliedgbi
ologicalgscience.gFromgagbasicgperspective,gthegstudygofgmicroorganismsginglaboratorygcult
ureghasgbeengthegprimarygmeansgbygwhichgthegfundamentalggeneticgandgbiochemicalgprope
rtiesgofglivinggcellsghavegbeengrevealed.gFromgangappliedgperspective,gmicroorganismsgdire
ctlygaffectgthegqualitygofghumanglifegingbothgdetrimentalgandgbeneficialgways.gAlthoughgmi
croorganismsgaregthegcausativegagentsgofgsomegofgthegmostgimportantghuman,ganimal,gandg
plantgdiseases,gtheygaregalsogusedgforgthegindustrialgproductiongofgantibiotics,gpharmaceutic
als,gandgfoods.gMicrobesgaregalsogincreasinglygbeinggusedgforgbeneficialgpurposesgasgdivers
egasgbioremediationgofgpollutedgsites,ggenegtherapiesgforggeneticgdiseases,gandgthegproducti
ongofgbiofuels.gMicrobiologygisgthereforegagsciencegofgfar-
reachinggscope,gwithgapplicationsgthatgaffectgthegqualitygofghumanglifegingagvarietygofgways
g(Figureg1.2).
Yougshouldgalsogemphasizegtogstudentsgthegimportancegofgmicroorganismsgingthegemerg
encegandgmaintenancegofghighergformsgofglife.gFromgthegproductiongofgmoleculargoxygeng(
bygcyanobacteria)gtogthegbiogeochemicalgcyclinggofgkeygelements,gsuchgasgcarbon,gnitrogen
,gandgsulfur,gmicroorganismsgplaygagmajorgrolegingsustaininggallglifegongthegplanet.gPointgo
utgingyourgcoursegintroductiongthatgforgallgthegreasonsgsummarizedgingthisgsection,gmicrobi
ologygisgthegfoundationgofgallgbiologicalgsciences.
1.2 |gStructuregandgActivitiesgofgMicrobialgCells
Becausegmicroorganismsggenerallygexistgasgfree-
livinggcells,gitgisgimportantgtogdiscussgthegcharacteristicsgofgcellsginggeneral.gEmphasizegthatgallgce
llsgexhibitgagnonrandomgorganizationgwithgagsemipermeablegmembranegboundarygthatgencompass
esganginternalgsystemgthatgisgnotgingequilibriumgwithgitsgenvironment.gPointgoutgthatgprokaryoticgc
ellsg(i.e.,gallgBacteriagandgArchaea)gdognotgcontaingmembrane-
bound,ginternalgorganellesgasgtraditionallygdescribedgforgeukaryoticgcellsg(thegEukarya;gFigureg1.4
mynursytest.store
,ACCESSgTestgBankgforgBrockgBiologygofgMicroorganismsg16thgEditiongMadi
gan
).gIngparticular,gthegorganizationgofgprokaryoticgDNAgasgagsinglegchromosomegingan
Copyrightg©g2021gPearsongEducation,gInc. CHAPTERg1gThegMicrobialgWorld 1
mynursytest.store
, ACCESSgTestgBankgforgBrockgBiologygofgMicroorganismsg16thgEditiongMadi
gan
arrangementgcalledgagnucleoid,gangaggregatedgmassgofggeneticgmaterialgwithingthegcytoplasm,gisging
starkgcontrastgtogthegcompartmentalized,gmultichromosomalgconfigurationgtypicallygfoundgingeukar
yotes.gHowever,gdespitegthegstructuralgandgmorphologicalgsimilaritiesgofgBacteriagandgArchaea,gma
kegsuregyourgstudentsgaregawaregearlygongthatgtheseggroupsgofgmicroorganismsghavegquitegdistinctge
volutionaryglineagesgandgare,gtherefore,gnotgcloselygrelatedgongaggeneticglevel.gThisgconceptgisgdisc
ussedgingmoregdetailgingSectiong1.5.
Thegabilitygofgcellsgtogmaintaingagthermodynamicgenergygflowgfargfromgequilibriumgd
efinesgwhatgwegrefergtogasgaglivinggsystem.gAllglivinggsystemsgdisplaygsomegformgofgenz
yme-drivengmetabolismgingwhichgbothgenergy-yieldingg(catabolic)gandgenergy-
gconsumingg(anabolic)gbiochemicalgreactionsgaregcatalyzedgconcurrently.gThesegchemica
lgtransformationsgallowgforgbiosynthesisgofgnewgcellgstructuresgand,gultimately,gcellgdivis
iong(microbialggrowth).gFigureg1.5gshowsgthegcharacteristicsgthatgdefinegcellularglife,gso
megofgwhichgareguniversalg(e.g.,gmetabolismgandgevolution)gandgsomegofgwhichgoccurgo
nlygingsomegcellsg(e.g.,gdifferentiationgandgmotility).
1.3 |gCellgSizegandgMorphology
Thegpresentationgingthegtextgofgthegsignificancegofgbeinggsmallgisgangimportantgconceptgforgstuden
tsgtoginternalizegasgtheygbegingtheirgstudygofgmicrobiology.gTableg1.1gshowsgthegwidegsizegrangeg
variabilitygofgbacterialgcells,gwhichgrangegfromgagdiametergofgaboutg0.2gµmgtogoverg700gµm.gUseg
thegtwogexamplesgofgunusuallyglargegbacteriagdiscussedgingthisgsectiongtogillustrategthegcurrentgup
perglimitgofgbacterialgcellgsize:g(1)gthegsurgeonfishggutgsymbiontgEpulopisciumgfishelsonig(>600gµ
mginglength;gFigureg1.6a),gandg(2)gthegsulfurgchemolithotrophgThiomargaritagnamibiensisg(750gµ
m;gFigureg1.6b).gThegevolutionaryg“rationale”gforgthegexistencegofgunusuallyglarge-
celledgbacteriagisgagmysterygwhengonegconsidersgthatgthegmetabolicgrategofgagcellgvariesginverselyg
withgthegsquaregofgitsgsize.gAskgyourgstudentsgforgideasgand/orghypothesesgthatgmightgexplaingtheg
selectivegadvantagegofglargegcellgsizegingthesegtwogprokaryotes.
Thegfactgthatgbacteriagcanglivegindependentlygasgsinglegcellsg(unlikegangindividualgcellgofgagmult
icellulargorganism)gsuggestsgthatgtheygmustgpossessgsomegcapabilitiesgthatgprovidegagselectivegadva
ntagegovergtheirgmulticellulargcounterpartsgthatgensuregtheirgsurvivalgongthegplanet.gSmallgcellsghave
gmoregsurfacegareagtogvolumeg(i.e.,gaghighergsurface-to-
volumegratio),gandgthisgalonegconfersgmanygofgthegevolutionarygadvantagesgofgbeinggsmall,gincludi
nggthegfollowing:
● Rapidgnutrientgandgwastegtransportgintogandgoutgofgthegcellgallowsgforgfastergmetabolicgratesga
ndggrowthgrates.
● Rapidggrowthgratesgresultgingthegrapidgproductiongofglargegpopulationsgofgcells.gThesegpopula
tions,gingturn,gcanggreatlygaffectgthegphysiochemicalgconditionsgofgangecosystemgwithingagsho
rtgtimegperiod.
● Transportgratesgaregagfunctiongofgthegsurfacegareagofgthegcytoplasmicgmembranegrelativegtogcell
gvolume.gUsegFigureg1.7gtogmathematicallygdemonstrategtogstudentsgthatgthegsurfacegareagofgag
spheregisgagfunctiongofgthegsquaregofgthegradius,gwhereasgthegvolumegofgagspheregisgagfunctiongofg
thegcubegofgthegradius.gThisgmeansgthatgthegsurface-to-
volumegratiogofgagsphericalgcellgcangbegexpressedgasg3/r,gwheregrgequalsgthegradiusgofgthegcell.g
Therefore,gagcoccusgcellghavinggagsmallergradiusghasgmoregsurfacegareagpergvolumegand,gthus,g
moregefficientgtransportgcapabilities,gthangagcoccusgcellghavinggaglargergradius.
● Ratesgofgevolutionarygchangegareghighergingsmaller,gfasterggrowingghaploidgcellsgthanginglarger,
2 INSTRUCTOR'SgMANUALgFORgBROCKgBIOLOGYgOFgMICROORGANISMS,g16e Copyrightg©g2021gPearsongEducation,gInc.
mynursytest.store
