MICROBIOLOGY LAB EXAM STUDY
GUIDE
WhataocoloraodoaoGram-Positiveaobacteriaaostain?ao-aoans--Purple
WhataocoloraodoaoGram-Negativeaobacteriaaostain?ao-aoans--Pink
Whataoareaotheao4aostepsaoofaoaaogramaoreaction?ao-aoans--
Primaryaostainaocrystalaoviolet,aomordantaoiodine,aodecolorizeraoalcohol-
acetone,aoandaocounterstainaosafranin.
Whataoareaosomeaowaysaoyouaocouldaomessaoupaoaaogramaostain?
aoAndaohowaowillaoyouaoknowaoyouaomessedaoup?ao-aoans--
a.aoNotaoheataofixingaoyouraoslideao-aoclearaoslide,
b.aooveraodecolorizingao-
aoslideaohasaobothaopinkaoandaopurpleaoevenaothoughaotheaocultureaowasaopure,aosoaogra
maopositiveaobacteriaaowillaostainaopinkaoandaopurple
c.aoUnderaodecolorizingao-
aoslideaohasaobothaopinkaoandaopurpleaoevenaothoughaotheaocultureaowasaopure,aosoaothea
ogramaonegativeaobacteriaaowillaostainaopurpleaoandaopinkao
d.aoOverheatingaoyouraoslideaooraonotaolettingaoyouraosmearaocompletelyaodryao-
aobacteriaaowillaoburnaooffaoleavingaoyouraoslideaoclear
e.aoForgettingaotoaocounterstainao-
aoyouaowillaohaveaogramaopositiveaobacteriaaothataoappearaopurpleaoandaogramaonegativea
obacteriaaowillaoappearaocolorless
Lookaooveraocellaoshapeaoandaoarrangementao(i.e.aococciaoandaostreptoao=aoStreptococcu
s)ao-aoans--
Lookaooveraocolonyaomorphologyaocharacteristicsao-aoans--
WhichaogrowsaobetteraoonaoMSAao(MannitolaoSaltaoAgar)aostaphylococcusaooraoenteroco
ccus?aoWhy?ao-aoans--
StaphylococcusaobacteriaaogrowsaobetteraoonaoMSAaobecauseaoitaohasaoaaohighaosaltaoco
ntentaothataomakesaoitaoveryaodifficultaoforaoenterococcusaobacteriaaotoaogrowaoonaoit.aoAls
oaosomeaostaphylococcusaospecies,aolikeaostaphylococcusaoaureus,aoareaoableaotoaoferm
entaotheaomannitolaoinaotheaoagaraoandaochangeaotheaopHaoofaotheaoagaraoasaoevidenceda
obyaoaaocoloraochangeaofromaopinkaotoaoyellow
WhataoisaoinaoBEAaoagaraothataomakesaoitaoselective?ao-aoans--
TheaoBileaosaltsaoinaotheaoBEAaoareaowhataomakeaoitaoselective
GUIDE
WhataocoloraodoaoGram-Positiveaobacteriaaostain?ao-aoans--Purple
WhataocoloraodoaoGram-Negativeaobacteriaaostain?ao-aoans--Pink
Whataoareaotheao4aostepsaoofaoaaogramaoreaction?ao-aoans--
Primaryaostainaocrystalaoviolet,aomordantaoiodine,aodecolorizeraoalcohol-
acetone,aoandaocounterstainaosafranin.
Whataoareaosomeaowaysaoyouaocouldaomessaoupaoaaogramaostain?
aoAndaohowaowillaoyouaoknowaoyouaomessedaoup?ao-aoans--
a.aoNotaoheataofixingaoyouraoslideao-aoclearaoslide,
b.aooveraodecolorizingao-
aoslideaohasaobothaopinkaoandaopurpleaoevenaothoughaotheaocultureaowasaopure,aosoaogra
maopositiveaobacteriaaowillaostainaopinkaoandaopurple
c.aoUnderaodecolorizingao-
aoslideaohasaobothaopinkaoandaopurpleaoevenaothoughaotheaocultureaowasaopure,aosoaothea
ogramaonegativeaobacteriaaowillaostainaopurpleaoandaopinkao
d.aoOverheatingaoyouraoslideaooraonotaolettingaoyouraosmearaocompletelyaodryao-
aobacteriaaowillaoburnaooffaoleavingaoyouraoslideaoclear
e.aoForgettingaotoaocounterstainao-
aoyouaowillaohaveaogramaopositiveaobacteriaaothataoappearaopurpleaoandaogramaonegativea
obacteriaaowillaoappearaocolorless
Lookaooveraocellaoshapeaoandaoarrangementao(i.e.aococciaoandaostreptoao=aoStreptococcu
s)ao-aoans--
Lookaooveraocolonyaomorphologyaocharacteristicsao-aoans--
WhichaogrowsaobetteraoonaoMSAao(MannitolaoSaltaoAgar)aostaphylococcusaooraoenteroco
ccus?aoWhy?ao-aoans--
StaphylococcusaobacteriaaogrowsaobetteraoonaoMSAaobecauseaoitaohasaoaaohighaosaltaoco
ntentaothataomakesaoitaoveryaodifficultaoforaoenterococcusaobacteriaaotoaogrowaoonaoit.aoAls
oaosomeaostaphylococcusaospecies,aolikeaostaphylococcusaoaureus,aoareaoableaotoaoferm
entaotheaomannitolaoinaotheaoagaraoandaochangeaotheaopHaoofaotheaoagaraoasaoevidenceda
obyaoaaocoloraochangeaofromaopinkaotoaoyellow
WhataoisaoinaoBEAaoagaraothataomakesaoitaoselective?ao-aoans--
TheaoBileaosaltsaoinaotheaoBEAaoareaowhataomakeaoitaoselective
