,ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
m m m m m m m m m m
an
CHAPTER
The Microbial World
m m
1
Summary
Chapterm1mintroducesmthemstudymofmmicrobiologymformstudents,mmostmofmwhommwi
llmhavemhadmlittlemormnomexposuremtomthemsubject.mConsequently,myoumhavemamgood
mopportunitymtomprovidemanmoverviewmofmmicrobiologymthatmdemonstratesmthemimp
ortantmrolesmmicroorganismsm(ormmicrobes)mplayminmhumanmactivitiesmandminmtheme
cologymofmthementirembiosphere.mThemabilitymofmmicroorganismsmtomexistmindepend
entlyminmnaturemasmfree-
livingmcellsmwithinmlargermmicrobialmcommunitiesm(Figurem1.1)mconfersmenormous
madaptivemadvantagesmovermcellsmofmmacroorganisms,m whichmaremincapablemofmanmi
ndependentmexistence.
1.1 | Microorganisms, Tiny Titans of the Earth
m m m m m m
Describemtomstudentsmwaysminmwhichmmicrobiologymservesmasmbothmambasicmandmanmappliedm
biologicalmscience.mFrommambasicmperspective,mthemstudymofmmicroorganismsminmlaboratorym
culturemhasmbeenmthemprimarymmeansmbymwhichmthemfundamentalmgeneticmandmbiochemicalm
propertiesmofmlivingmcellsmhavembeenmrevealed.mFrommanmappliedmperspective,mmicroorganis
msmdirectlymaffectmthemqualitymofmhumanmlifeminmbothmdetrimentalmandmbeneficialmways.mAlth
oughmmicroorganismsmaremthemcausativemagentsmofmsomemofmthemmostmimportantmhuman,man
imal,mandmplantmdiseases,mtheymaremalsomusedmformthemindustrialmproductionmofmantibiotics,mp
harmaceuticals,mandmfoods.mMicrobesmaremalsomincreasinglymbeingmusedmformbeneficialmpurp
osesmasmdiversemasmbioremediationmofmpollutedmsites,mgenemtherapiesmformgeneticmdiseases,ma
ndmthemproductionmofmbiofuels.mMicrobiologymismthereforemamsciencemofmfar-
reachingmscope,mwithmapplicationsmthatmaffectmthemqualitymofmhumanmlifeminmamvarietymofmwa
ysm(Figurem1.2).
Youmshouldmalsomemphasizemtomstudentsmthemimportancemofmmicroorganismsminmthemem
ergencemandmmaintenancemofmhighermformsmofmlife.mFrommthemproductionmofmmolecularmox
ygenm(bymcyanobacteria)mtomthembiogeochemicalmcyclingmofmkeymelements,msuchmasmcarbon
,mnitrogen,mandmsulfur,mmicroorganismsmplaymammajormroleminmsustainingmallmlifemonmthempla
net.mPointmoutminmyourmcoursemintroductionmthatmformallmthemreasonsmsummarizedminmthismse
ction,mmicrobiologymismthemfoundationmofmallmbiologicalmsciences.
1.2 | Structure and Activities of Microbial Cells
m m m m m m
Becausemmicroorganismsmgenerallymexistmasmfree-
livingmcells,mitmismimportantmtomdiscussmthemcharacteristicsmofmcellsminmgeneral.mEmphasizemthatmallm
cellsmexhibitmamnonrandommorganizationmwithmamsemipermeablemmembranemboundarymthatmencompa
ssesmanminternalmsystemmthatmismnotminmequilibriummwithmitsmenvironment.mPointmoutmthatmprokaryoti
cmcellsm(i.e.,mallmBacteriamandmArchaea)mdomnotmcontainmmembrane-
bound,minternalmorganellesmasmtraditionallymdescribedmformeukaryoticmcellsm(themEukarya;mFigurem1.
4).mInmparticular,mthemorganizationmofmprokaryoticmDNAmasmamsinglemchromosomeminman
mynursytest.store
,ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
m m m m m m m m m m
an
Copyrightm©m2021mPearsonmEducation,mInc. CHAPTERm1mThemMicrobialmWorld 1
mynursytest.store
, ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
m m m m m m m m m m
an
arrangementmcalledmamnucleoid,manmaggregatedmmassmofmgeneticmmaterialmwithinmthemcytoplasm,mismin
mstarkmcontrastmtomthemcompartmentalized,mmultichromosomalmconfigurationmtypicallymfoundminmeuka
ryotes.mHowever,mdespitemthemstructuralmandmmorphologicalmsimilaritiesmofmBacteriamandmArchaea,mma
kemsuremyourmstudentsmaremawaremearlymonmthatmthesemgroupsmofmmicroorganismsmhavemquitemdistinctm
evolutionarymlineagesmandmare,mtherefore,mnotmcloselymrelatedmonmamgeneticmlevel.mThismconceptmismdis
cussedminmmoremdetailminmSectionm1.5.
Themabilitymofmcellsmtommaintainmamthermodynamicmenergymflowmfarmfrommequilibriumm
definesmwhatmwemrefermtomasmamlivingmsystem.mAllmlivingmsystemsmdisplaymsomemformmofme
nzyme-drivenmmetabolismminmwhichmbothmenergy-yieldingm(catabolic)mandmenergy-
mconsumingm(anabolic)mbiochemicalmreactionsmaremcatalyzedmconcurrently.mThesemchemic
almtransformationsmallowmformbiosynthesismofmnewmcellmstructuresmand,multimately,mcellmdi
visionm(microbialmgrowth).mFigurem1.5mshowsmthemcharacteristicsmthatmdefinemcellularmlife,
msomemofmwhichmaremuniversalm(e.g.,mmetabolismmandmevolution)mandmsomemofmwhichmocc
urmonlyminmsomemcellsm(e.g.,mdifferentiationmandmmotility).
1.3 | Cell Size and Morphology
m m m m
Thempresentationminmthemtextmofmthemsignificancemofmbeingmsmallmismanmimportantmconceptmformstude
ntsmtominternalizemasmtheymbeginmtheirmstudymofmmicrobiology.mTablem1.1mshowsmthemwidemsizemrang
emvariabilitymofmbacterialmcells,mwhichmrangemfrommamdiametermofmaboutm0.2mµmmtomoverm700mµm.m
Usemthemtwomexamplesmofmunusuallymlargembacteriamdiscussedminmthismsectionmtomillustratemthemcurre
ntmuppermlimitmofmbacterialmcellmsize:m(1)mthemsurgeonfishmgutmsymbiontmEpulopisciummfishelsonim(>
600mµmminmlength;mFigurem1.6a),mandm(2)mthemsulfurmchemolithotrophmThiomargaritamnamibiensism(
750mµm;mFigurem1.6b).mThemevolutionarym“rationale”mformthemexistencemofmunusuallymlarge-
celledmbacteriamismammysterymwhenmonemconsidersmthatmthemmetabolicmratemofmamcellmvariesminversel
ymwithmthemsquaremofmitsmsize.mAskmyourmstudentsmformideasmand/ormhypothesesmthatmmightmexplainmt
hemselectivemadvantagemofmlargemcellmsizeminmthesemtwomprokaryotes.
Themfactmthatmbacteriamcanmlivemindependentlymasmsinglemcellsm(unlikemanmindividualmcellmofmamm
ulticellularmorganism)msuggestsmthatmtheymmustmpossessmsomemcapabilitiesmthatmprovidemamselectivem
advantagemovermtheirmmulticellularmcounterpartsmthatmensuremtheirmsurvivalmonmthemplanet.mSmallmce
llsmhavemmoremsurfacemareamtomvolumem(i.e.,mamhighermsurface-to-
volumemratio),mandmthismalonemconfersmmanymofmthemevolutionarymadvantagesmofmbeingmsmall,minclu
dingmthemfollowing:
● Rapidmnutrientmandmwastemtransportmintomandmoutmofmthemcellmallowsmformfastermmetabolicmrates
mandm growthmrates.
● Rapidmgrowthmratesmresultminmthemrapidmproductionmofmlargempopulationsmofmcells.mThesempopul
ations,minmturn,mcanmgreatlymaffectmthemphysiochemicalmconditionsmofmanmecosystemmwithinmamsh
ortmtimemperiod.
● Transportmratesmaremamfunctionmofmthemsurfacemareamofmthemcytoplasmicmmembranemrelativemtomc
ellmvolume.mUsemFigurem1.7mtommathematicallymdemonstratemtomstudentsmthatmthemsurfacemaream
ofmamspheremismamfunctionmofmthemsquaremofmthemradius,mwhereasmthemvolumemofmamspheremismamfunct
ionmofmthemcubemofmthemradius.mThismmeansmthatmthemsurface-to-
volumemratiomofmamsphericalmcellmcanmbemexpressedmasm3/r,mwheremrmequalsmthemradiusmofmthemcel
l.mTherefore,mamcoccusmcellmhavingmamsmallermradiusmhasmmoremsurfacemareampermvolumemand,mthu
s,mmoremefficientmtransportmcapabilities,mthanmamcoccusmcellmhavingmamlargermradius.
● Ratesmofmevolutionarymchangemaremhigherminmsmaller,mfastermgrowingmhaploidmcellsmthanminmlarger
,
mynursytest.store
m m m m m m m m m m
an
CHAPTER
The Microbial World
m m
1
Summary
Chapterm1mintroducesmthemstudymofmmicrobiologymformstudents,mmostmofmwhommwi
llmhavemhadmlittlemormnomexposuremtomthemsubject.mConsequently,myoumhavemamgood
mopportunitymtomprovidemanmoverviewmofmmicrobiologymthatmdemonstratesmthemimp
ortantmrolesmmicroorganismsm(ormmicrobes)mplayminmhumanmactivitiesmandminmtheme
cologymofmthementirembiosphere.mThemabilitymofmmicroorganismsmtomexistmindepend
entlyminmnaturemasmfree-
livingmcellsmwithinmlargermmicrobialmcommunitiesm(Figurem1.1)mconfersmenormous
madaptivemadvantagesmovermcellsmofmmacroorganisms,m whichmaremincapablemofmanmi
ndependentmexistence.
1.1 | Microorganisms, Tiny Titans of the Earth
m m m m m m
Describemtomstudentsmwaysminmwhichmmicrobiologymservesmasmbothmambasicmandmanmappliedm
biologicalmscience.mFrommambasicmperspective,mthemstudymofmmicroorganismsminmlaboratorym
culturemhasmbeenmthemprimarymmeansmbymwhichmthemfundamentalmgeneticmandmbiochemicalm
propertiesmofmlivingmcellsmhavembeenmrevealed.mFrommanmappliedmperspective,mmicroorganis
msmdirectlymaffectmthemqualitymofmhumanmlifeminmbothmdetrimentalmandmbeneficialmways.mAlth
oughmmicroorganismsmaremthemcausativemagentsmofmsomemofmthemmostmimportantmhuman,man
imal,mandmplantmdiseases,mtheymaremalsomusedmformthemindustrialmproductionmofmantibiotics,mp
harmaceuticals,mandmfoods.mMicrobesmaremalsomincreasinglymbeingmusedmformbeneficialmpurp
osesmasmdiversemasmbioremediationmofmpollutedmsites,mgenemtherapiesmformgeneticmdiseases,ma
ndmthemproductionmofmbiofuels.mMicrobiologymismthereforemamsciencemofmfar-
reachingmscope,mwithmapplicationsmthatmaffectmthemqualitymofmhumanmlifeminmamvarietymofmwa
ysm(Figurem1.2).
Youmshouldmalsomemphasizemtomstudentsmthemimportancemofmmicroorganismsminmthemem
ergencemandmmaintenancemofmhighermformsmofmlife.mFrommthemproductionmofmmolecularmox
ygenm(bymcyanobacteria)mtomthembiogeochemicalmcyclingmofmkeymelements,msuchmasmcarbon
,mnitrogen,mandmsulfur,mmicroorganismsmplaymammajormroleminmsustainingmallmlifemonmthempla
net.mPointmoutminmyourmcoursemintroductionmthatmformallmthemreasonsmsummarizedminmthismse
ction,mmicrobiologymismthemfoundationmofmallmbiologicalmsciences.
1.2 | Structure and Activities of Microbial Cells
m m m m m m
Becausemmicroorganismsmgenerallymexistmasmfree-
livingmcells,mitmismimportantmtomdiscussmthemcharacteristicsmofmcellsminmgeneral.mEmphasizemthatmallm
cellsmexhibitmamnonrandommorganizationmwithmamsemipermeablemmembranemboundarymthatmencompa
ssesmanminternalmsystemmthatmismnotminmequilibriummwithmitsmenvironment.mPointmoutmthatmprokaryoti
cmcellsm(i.e.,mallmBacteriamandmArchaea)mdomnotmcontainmmembrane-
bound,minternalmorganellesmasmtraditionallymdescribedmformeukaryoticmcellsm(themEukarya;mFigurem1.
4).mInmparticular,mthemorganizationmofmprokaryoticmDNAmasmamsinglemchromosomeminman
mynursytest.store
,ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
m m m m m m m m m m
an
Copyrightm©m2021mPearsonmEducation,mInc. CHAPTERm1mThemMicrobialmWorld 1
mynursytest.store
, ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
m m m m m m m m m m
an
arrangementmcalledmamnucleoid,manmaggregatedmmassmofmgeneticmmaterialmwithinmthemcytoplasm,mismin
mstarkmcontrastmtomthemcompartmentalized,mmultichromosomalmconfigurationmtypicallymfoundminmeuka
ryotes.mHowever,mdespitemthemstructuralmandmmorphologicalmsimilaritiesmofmBacteriamandmArchaea,mma
kemsuremyourmstudentsmaremawaremearlymonmthatmthesemgroupsmofmmicroorganismsmhavemquitemdistinctm
evolutionarymlineagesmandmare,mtherefore,mnotmcloselymrelatedmonmamgeneticmlevel.mThismconceptmismdis
cussedminmmoremdetailminmSectionm1.5.
Themabilitymofmcellsmtommaintainmamthermodynamicmenergymflowmfarmfrommequilibriumm
definesmwhatmwemrefermtomasmamlivingmsystem.mAllmlivingmsystemsmdisplaymsomemformmofme
nzyme-drivenmmetabolismminmwhichmbothmenergy-yieldingm(catabolic)mandmenergy-
mconsumingm(anabolic)mbiochemicalmreactionsmaremcatalyzedmconcurrently.mThesemchemic
almtransformationsmallowmformbiosynthesismofmnewmcellmstructuresmand,multimately,mcellmdi
visionm(microbialmgrowth).mFigurem1.5mshowsmthemcharacteristicsmthatmdefinemcellularmlife,
msomemofmwhichmaremuniversalm(e.g.,mmetabolismmandmevolution)mandmsomemofmwhichmocc
urmonlyminmsomemcellsm(e.g.,mdifferentiationmandmmotility).
1.3 | Cell Size and Morphology
m m m m
Thempresentationminmthemtextmofmthemsignificancemofmbeingmsmallmismanmimportantmconceptmformstude
ntsmtominternalizemasmtheymbeginmtheirmstudymofmmicrobiology.mTablem1.1mshowsmthemwidemsizemrang
emvariabilitymofmbacterialmcells,mwhichmrangemfrommamdiametermofmaboutm0.2mµmmtomoverm700mµm.m
Usemthemtwomexamplesmofmunusuallymlargembacteriamdiscussedminmthismsectionmtomillustratemthemcurre
ntmuppermlimitmofmbacterialmcellmsize:m(1)mthemsurgeonfishmgutmsymbiontmEpulopisciummfishelsonim(>
600mµmminmlength;mFigurem1.6a),mandm(2)mthemsulfurmchemolithotrophmThiomargaritamnamibiensism(
750mµm;mFigurem1.6b).mThemevolutionarym“rationale”mformthemexistencemofmunusuallymlarge-
celledmbacteriamismammysterymwhenmonemconsidersmthatmthemmetabolicmratemofmamcellmvariesminversel
ymwithmthemsquaremofmitsmsize.mAskmyourmstudentsmformideasmand/ormhypothesesmthatmmightmexplainmt
hemselectivemadvantagemofmlargemcellmsizeminmthesemtwomprokaryotes.
Themfactmthatmbacteriamcanmlivemindependentlymasmsinglemcellsm(unlikemanmindividualmcellmofmamm
ulticellularmorganism)msuggestsmthatmtheymmustmpossessmsomemcapabilitiesmthatmprovidemamselectivem
advantagemovermtheirmmulticellularmcounterpartsmthatmensuremtheirmsurvivalmonmthemplanet.mSmallmce
llsmhavemmoremsurfacemareamtomvolumem(i.e.,mamhighermsurface-to-
volumemratio),mandmthismalonemconfersmmanymofmthemevolutionarymadvantagesmofmbeingmsmall,minclu
dingmthemfollowing:
● Rapidmnutrientmandmwastemtransportmintomandmoutmofmthemcellmallowsmformfastermmetabolicmrates
mandm growthmrates.
● Rapidmgrowthmratesmresultminmthemrapidmproductionmofmlargempopulationsmofmcells.mThesempopul
ations,minmturn,mcanmgreatlymaffectmthemphysiochemicalmconditionsmofmanmecosystemmwithinmamsh
ortmtimemperiod.
● Transportmratesmaremamfunctionmofmthemsurfacemareamofmthemcytoplasmicmmembranemrelativemtomc
ellmvolume.mUsemFigurem1.7mtommathematicallymdemonstratemtomstudentsmthatmthemsurfacemaream
ofmamspheremismamfunctionmofmthemsquaremofmthemradius,mwhereasmthemvolumemofmamspheremismamfunct
ionmofmthemcubemofmthemradius.mThismmeansmthatmthemsurface-to-
volumemratiomofmamsphericalmcellmcanmbemexpressedmasm3/r,mwheremrmequalsmthemradiusmofmthemcel
l.mTherefore,mamcoccusmcellmhavingmamsmallermradiusmhasmmoremsurfacemareampermvolumemand,mthu
s,mmoremefficientmtransportmcapabilities,mthanmamcoccusmcellmhavingmamlargermradius.
● Ratesmofmevolutionarymchangemaremhigherminmsmaller,mfastermgrowingmhaploidmcellsmthanminmlarger
,
mynursytest.store
