,ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
g g g g g g g g g g
an
CHAPTER
The Microbial World
g g
1
Summary
Chapterg1gintroducesgthegstudygofgmicrobiologygforgstudents,gmostgofgwhomgwillgha
veghadglittlegorgnogexposuregtogthegsubject.gConsequently,gyoughavegaggoodgopportu
nitygtogprovidegangoverviewgofgmicrobiologygthatgdemonstratesgthegimportantgrolesg
microorganismsg(orgmicrobes)gplayginghumangactivitiesgandgingthegecologygofgthege
ntiregbiosphere.gThegabilitygofgmicroorganismsgtogexistgindependentlygingnaturegasgf
ree-
livinggcellsgwithinglargergmicrobialgcommunitiesg(Figureg1.1)gconfersgenormousgad
aptivegadvantagesgovergcellsgofgmacroorganisms,gwhichgaregincapablegofgangindepe
ndentgexistence.
1.1 | Microorganisms, Tiny Titans of the Earth
g g g g g g
Describegtogstudentsgwaysgingwhichgmicrobiologygservesgasgbothgagbasicgandgangappliedgbiolo
gicalgscience.gFromgagbasicgperspective,gthegstudygofgmicroorganismsginglaboratorygculturegh
asgbeengthegprimarygmeansgbygwhichgthegfundamentalggeneticgandgbiochemicalgpropertiesgofg
livinggcellsghavegbeengrevealed.gFromgangappliedgperspective,gmicroorganismsgdirectlygaffectg
thegqualitygofghumanglifegingbothgdetrimentalgandgbeneficialgways.gAlthoughgmicroorganisms
garegthegcausativegagentsgofgsomegofgthegmostgimportantghuman,ganimal,gandgplantgdiseases,gth
eygaregalsogusedgforgthegindustrialgproductiongofgantibiotics,gpharmaceuticals,gandgfoods.gMic
robesgaregalsogincreasinglygbeinggusedgforgbeneficialgpurposesgasgdiversegasgbioremediationgo
fgpollutedgsites,ggenegtherapiesgforggeneticgdiseases,gandgthegproductiongofgbiofuels.gMicrobio
logygisgthereforegagsciencegofgfar-
reachinggscope,gwithgapplicationsgthatgaffectgthegqualitygofghumanglifegingagvarietygofgwaysg(F
igureg1.2).
Yougshouldgalsogemphasizegtogstudentsgthegimportancegofgmicroorganismsgingthegemerge
ncegandgmaintenancegofghighergformsgofglife.gFromgthegproductiongofgmoleculargoxygeng(by
gcyanobacteria)gtogthegbiogeochemicalgcyclinggofgkeygelements,gsuchgasgcarbon,gnitrogen,gan
dgsulfur,gmicroorganismsgplaygagmajorgrolegingsustaininggallglifegongthegplanet.gPointgoutgingy
ourgcoursegintroductiongthatgforgallgthegreasonsgsummarizedgingthisgsection,gmicrobiologygisg
thegfoundationgofgallgbiologicalgsciences.
1.2 | Structure and Activities of Microbial Cells
g g g g g g
Becausegmicroorganismsggenerallygexistgasgfree-
livinggcells,gitgisgimportantgtogdiscussgthegcharacteristicsgofgcellsginggeneral.gEmphasizegthatgallgcellsg
exhibitgagnonrandomgorganizationgwithgagsemipermeablegmembranegboundarygthatgencompassesgangi
nternalgsystemgthatgisgnotgingequilibriumgwithgitsgenvironment.gPointgoutgthatgprokaryoticgcellsg(i.e.,ga
llgBacteriagandgArchaea)gdognotgcontaingmembrane-
bound,ginternalgorganellesgasgtraditionallygdescribedgforgeukaryoticgcellsg(thegEukarya;gFigureg1.4).gI
ngparticular,gthegorganizationgofgprokaryoticgDNAgasgagsinglegchromosomegingan
mynursytest.store
,ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
g g g g g g g g g g
an
Copyrightg©g2021gPearsongEducation,gInc. CHAPTERg1gThegMicrobialgWorld 1
mynursytest.store
, ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
g g g g g g g g g g
an
arrangementgcalledgagnucleoid,gangaggregatedgmassgofggeneticgmaterialgwithingthegcytoplasm,gisgingstar
kgcontrastgtogthegcompartmentalized,gmultichromosomalgconfigurationgtypicallygfoundgingeukaryotes.g
However,gdespitegthegstructuralgandgmorphologicalgsimilaritiesgofgBacteriagandgArchaea,gmakegsuregyo
urgstudentsgaregawaregearlygongthatgtheseggroupsgofgmicroorganismsghavegquitegdistinctgevolutionaryglin
eagesgandgare,gtherefore,gnotgcloselygrelatedgongaggeneticglevel.gThisgconceptgisgdiscussedgingmoregdetail
gingSectiong1.5.
Thegabilitygofgcellsgtogmaintaingagthermodynamicgenergygflowgfargfromgequilibriumgdefi
nesgwhatgwegrefergtogasgaglivinggsystem.gAllglivinggsystemsgdisplaygsomegformgofgenzyme-
drivengmetabolismgingwhichgbothgenergy-yieldingg(catabolic)gandgenergy-
gconsumingg(anabolic)gbiochemicalgreactionsgaregcatalyzedgconcurrently.gThesegchemicalgt
ransformationsgallowgforgbiosynthesisgofgnewgcellgstructuresgand,gultimately,gcellgdivisiong(
microbialggrowth).gFigureg1.5gshowsgthegcharacteristicsgthatgdefinegcellularglife,gsomegofgw
hichgareguniversalg(e.g.,gmetabolismgandgevolution)gandgsomegofgwhichgoccurgonlygingsome
gcellsg(e.g.,gdifferentiationgandgmotility).
1.3 | Cell Size and Morphology
g g g g
Thegpresentationgingthegtextgofgthegsignificancegofgbeinggsmallgisgangimportantgconceptgforgstudentsgto
ginternalizegasgtheygbegingtheirgstudygofgmicrobiology.gTableg1.1gshowsgthegwidegsizegrangegvariabilit
ygofgbacterialgcells,gwhichgrangegfromgagdiametergofgaboutg0.2gµmgtogoverg700gµm.gUsegthegtwogexam
plesgofgunusuallyglargegbacteriagdiscussedgingthisgsectiongtogillustrategthegcurrentgupperglimitgofgbacte
rialgcellgsize:g(1)gthegsurgeonfishggutgsymbiontgEpulopisciumgfishelsonig(>600gµmginglength;gFigureg
1.6a),gandg(2)gthegsulfurgchemolithotrophgThiomargaritagnamibiensisg(750gµm;gFigureg1.6b).gThegev
olutionaryg“rationale”gforgthegexistencegofgunusuallyglarge-
celledgbacteriagisgagmysterygwhengonegconsidersgthatgthegmetabolicgrategofgagcellgvariesginverselygwit
hgthegsquaregofgitsgsize.gAskgyourgstudentsgforgideasgand/orghypothesesgthatgmightgexplaingthegselecti
vegadvantagegofglargegcellgsizegingthesegtwogprokaryotes.
Thegfactgthatgbacteriagcanglivegindependentlygasgsinglegcellsg(unlikegangindividualgcellgofgagmultic
ellulargorganism)gsuggestsgthatgtheygmustgpossessgsomegcapabilitiesgthatgprovidegagselectivegadvanta
gegovergtheirgmulticellulargcounterpartsgthatgensuregtheirgsurvivalgongthegplanet.gSmallgcellsghavegmor
egsurfacegareagtogvolumeg(i.e.,gaghighergsurface-to-
volumegratio),gandgthisgalonegconfersgmanygofgthegevolutionarygadvantagesgofgbeinggsmall,gincluding
gthegfollowing:
● Rapidgnutrientgandgwastegtransportgintogandgoutgofgthegcellgallowsgforgfastergmetabolicgratesgandg
growthgrates.
● Rapidggrowthgratesgresultgingthegrapidgproductiongofglargegpopulationsgofgcells.gThesegpopulatio
ns,gingturn,gcanggreatlygaffectgthegphysiochemicalgconditionsgofgangecosystemgwithingagshortgtime
gperiod.
● Transportgratesgaregagfunctiongofgthegsurfacegareagofgthegcytoplasmicgmembranegrelativegtogcellgv
olume.gUsegFigureg1.7gtogmathematicallygdemonstrategtogstudentsgthatgthegsurfacegareagofgagsphe
regisgagfunctiongofgthegsquaregofgthegradius,gwhereasgthegvolumegofgagspheregisgagfunctiongofgthegcubeg
ofgthegradius.gThisgmeansgthatgthegsurface-to-
volumegratiogofgagsphericalgcellgcangbegexpressedgasg3/r,gwheregrgequalsgthegradiusgofgthegcell.gTh
erefore,gagcoccusgcellghavinggagsmallergradiusghasgmoregsurfacegareagpergvolumegand,gthus,gmoregef
ficientgtransportgcapabilities,gthangagcoccusgcellghavinggaglargergradius.
● Ratesgofgevolutionarygchangegareghighergingsmaller,gfasterggrowingghaploidgcellsgthanginglarger,
2 INSTRUCTOR'SgMANUALgFORgBROCKgBIOLOGYgOFgMICROORGANISMS,g16e Copyrightg©g2021gPearsongEducation,gInc.
mynursytest.store
g g g g g g g g g g
an
CHAPTER
The Microbial World
g g
1
Summary
Chapterg1gintroducesgthegstudygofgmicrobiologygforgstudents,gmostgofgwhomgwillgha
veghadglittlegorgnogexposuregtogthegsubject.gConsequently,gyoughavegaggoodgopportu
nitygtogprovidegangoverviewgofgmicrobiologygthatgdemonstratesgthegimportantgrolesg
microorganismsg(orgmicrobes)gplayginghumangactivitiesgandgingthegecologygofgthege
ntiregbiosphere.gThegabilitygofgmicroorganismsgtogexistgindependentlygingnaturegasgf
ree-
livinggcellsgwithinglargergmicrobialgcommunitiesg(Figureg1.1)gconfersgenormousgad
aptivegadvantagesgovergcellsgofgmacroorganisms,gwhichgaregincapablegofgangindepe
ndentgexistence.
1.1 | Microorganisms, Tiny Titans of the Earth
g g g g g g
Describegtogstudentsgwaysgingwhichgmicrobiologygservesgasgbothgagbasicgandgangappliedgbiolo
gicalgscience.gFromgagbasicgperspective,gthegstudygofgmicroorganismsginglaboratorygculturegh
asgbeengthegprimarygmeansgbygwhichgthegfundamentalggeneticgandgbiochemicalgpropertiesgofg
livinggcellsghavegbeengrevealed.gFromgangappliedgperspective,gmicroorganismsgdirectlygaffectg
thegqualitygofghumanglifegingbothgdetrimentalgandgbeneficialgways.gAlthoughgmicroorganisms
garegthegcausativegagentsgofgsomegofgthegmostgimportantghuman,ganimal,gandgplantgdiseases,gth
eygaregalsogusedgforgthegindustrialgproductiongofgantibiotics,gpharmaceuticals,gandgfoods.gMic
robesgaregalsogincreasinglygbeinggusedgforgbeneficialgpurposesgasgdiversegasgbioremediationgo
fgpollutedgsites,ggenegtherapiesgforggeneticgdiseases,gandgthegproductiongofgbiofuels.gMicrobio
logygisgthereforegagsciencegofgfar-
reachinggscope,gwithgapplicationsgthatgaffectgthegqualitygofghumanglifegingagvarietygofgwaysg(F
igureg1.2).
Yougshouldgalsogemphasizegtogstudentsgthegimportancegofgmicroorganismsgingthegemerge
ncegandgmaintenancegofghighergformsgofglife.gFromgthegproductiongofgmoleculargoxygeng(by
gcyanobacteria)gtogthegbiogeochemicalgcyclinggofgkeygelements,gsuchgasgcarbon,gnitrogen,gan
dgsulfur,gmicroorganismsgplaygagmajorgrolegingsustaininggallglifegongthegplanet.gPointgoutgingy
ourgcoursegintroductiongthatgforgallgthegreasonsgsummarizedgingthisgsection,gmicrobiologygisg
thegfoundationgofgallgbiologicalgsciences.
1.2 | Structure and Activities of Microbial Cells
g g g g g g
Becausegmicroorganismsggenerallygexistgasgfree-
livinggcells,gitgisgimportantgtogdiscussgthegcharacteristicsgofgcellsginggeneral.gEmphasizegthatgallgcellsg
exhibitgagnonrandomgorganizationgwithgagsemipermeablegmembranegboundarygthatgencompassesgangi
nternalgsystemgthatgisgnotgingequilibriumgwithgitsgenvironment.gPointgoutgthatgprokaryoticgcellsg(i.e.,ga
llgBacteriagandgArchaea)gdognotgcontaingmembrane-
bound,ginternalgorganellesgasgtraditionallygdescribedgforgeukaryoticgcellsg(thegEukarya;gFigureg1.4).gI
ngparticular,gthegorganizationgofgprokaryoticgDNAgasgagsinglegchromosomegingan
mynursytest.store
,ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
g g g g g g g g g g
an
Copyrightg©g2021gPearsongEducation,gInc. CHAPTERg1gThegMicrobialgWorld 1
mynursytest.store
, ACCESS Test Bank for Brock Biology of Microorganisms 16th EditionMadig
g g g g g g g g g g
an
arrangementgcalledgagnucleoid,gangaggregatedgmassgofggeneticgmaterialgwithingthegcytoplasm,gisgingstar
kgcontrastgtogthegcompartmentalized,gmultichromosomalgconfigurationgtypicallygfoundgingeukaryotes.g
However,gdespitegthegstructuralgandgmorphologicalgsimilaritiesgofgBacteriagandgArchaea,gmakegsuregyo
urgstudentsgaregawaregearlygongthatgtheseggroupsgofgmicroorganismsghavegquitegdistinctgevolutionaryglin
eagesgandgare,gtherefore,gnotgcloselygrelatedgongaggeneticglevel.gThisgconceptgisgdiscussedgingmoregdetail
gingSectiong1.5.
Thegabilitygofgcellsgtogmaintaingagthermodynamicgenergygflowgfargfromgequilibriumgdefi
nesgwhatgwegrefergtogasgaglivinggsystem.gAllglivinggsystemsgdisplaygsomegformgofgenzyme-
drivengmetabolismgingwhichgbothgenergy-yieldingg(catabolic)gandgenergy-
gconsumingg(anabolic)gbiochemicalgreactionsgaregcatalyzedgconcurrently.gThesegchemicalgt
ransformationsgallowgforgbiosynthesisgofgnewgcellgstructuresgand,gultimately,gcellgdivisiong(
microbialggrowth).gFigureg1.5gshowsgthegcharacteristicsgthatgdefinegcellularglife,gsomegofgw
hichgareguniversalg(e.g.,gmetabolismgandgevolution)gandgsomegofgwhichgoccurgonlygingsome
gcellsg(e.g.,gdifferentiationgandgmotility).
1.3 | Cell Size and Morphology
g g g g
Thegpresentationgingthegtextgofgthegsignificancegofgbeinggsmallgisgangimportantgconceptgforgstudentsgto
ginternalizegasgtheygbegingtheirgstudygofgmicrobiology.gTableg1.1gshowsgthegwidegsizegrangegvariabilit
ygofgbacterialgcells,gwhichgrangegfromgagdiametergofgaboutg0.2gµmgtogoverg700gµm.gUsegthegtwogexam
plesgofgunusuallyglargegbacteriagdiscussedgingthisgsectiongtogillustrategthegcurrentgupperglimitgofgbacte
rialgcellgsize:g(1)gthegsurgeonfishggutgsymbiontgEpulopisciumgfishelsonig(>600gµmginglength;gFigureg
1.6a),gandg(2)gthegsulfurgchemolithotrophgThiomargaritagnamibiensisg(750gµm;gFigureg1.6b).gThegev
olutionaryg“rationale”gforgthegexistencegofgunusuallyglarge-
celledgbacteriagisgagmysterygwhengonegconsidersgthatgthegmetabolicgrategofgagcellgvariesginverselygwit
hgthegsquaregofgitsgsize.gAskgyourgstudentsgforgideasgand/orghypothesesgthatgmightgexplaingthegselecti
vegadvantagegofglargegcellgsizegingthesegtwogprokaryotes.
Thegfactgthatgbacteriagcanglivegindependentlygasgsinglegcellsg(unlikegangindividualgcellgofgagmultic
ellulargorganism)gsuggestsgthatgtheygmustgpossessgsomegcapabilitiesgthatgprovidegagselectivegadvanta
gegovergtheirgmulticellulargcounterpartsgthatgensuregtheirgsurvivalgongthegplanet.gSmallgcellsghavegmor
egsurfacegareagtogvolumeg(i.e.,gaghighergsurface-to-
volumegratio),gandgthisgalonegconfersgmanygofgthegevolutionarygadvantagesgofgbeinggsmall,gincluding
gthegfollowing:
● Rapidgnutrientgandgwastegtransportgintogandgoutgofgthegcellgallowsgforgfastergmetabolicgratesgandg
growthgrates.
● Rapidggrowthgratesgresultgingthegrapidgproductiongofglargegpopulationsgofgcells.gThesegpopulatio
ns,gingturn,gcanggreatlygaffectgthegphysiochemicalgconditionsgofgangecosystemgwithingagshortgtime
gperiod.
● Transportgratesgaregagfunctiongofgthegsurfacegareagofgthegcytoplasmicgmembranegrelativegtogcellgv
olume.gUsegFigureg1.7gtogmathematicallygdemonstrategtogstudentsgthatgthegsurfacegareagofgagsphe
regisgagfunctiongofgthegsquaregofgthegradius,gwhereasgthegvolumegofgagspheregisgagfunctiongofgthegcubeg
ofgthegradius.gThisgmeansgthatgthegsurface-to-
volumegratiogofgagsphericalgcellgcangbegexpressedgasg3/r,gwheregrgequalsgthegradiusgofgthegcell.gTh
erefore,gagcoccusgcellghavinggagsmallergradiusghasgmoregsurfacegareagpergvolumegand,gthus,gmoregef
ficientgtransportgcapabilities,gthangagcoccusgcellghavinggaglargergradius.
● Ratesgofgevolutionarygchangegareghighergingsmaller,gfasterggrowingghaploidgcellsgthanginglarger,
2 INSTRUCTOR'SgMANUALgFORgBROCKgBIOLOGYgOFgMICROORGANISMS,g16e Copyrightg©g2021gPearsongEducation,gInc.
mynursytest.store
