MicrobiologyMcGrawHillLabExam
withcorrectanswers
YouareobservingStreptococcuspneumoniaeonaslide thathasbeenstainedusingthecapsular
stainingmethod.However,youdonotseecapsulessurroundingthecellsasyouexpected.Whatisa
likelyreasonforthis?
Theslidewasheatfixed,whichcanshrinkordestroycapsules.
Correct OrderofStepsto PerformaCapsuleStain
Applyprimarystain(indiainkornigrosin)toacleanslide.
Useinoculatinglooptoasepticallymixbacterial samplewithprimarystain.
Createathinsmearbydraggingacleanslide throughthesample.
Allowsampletothoroughlyairdry.
Applysecondarystain(crystalviolet)tosmear.
Rinsewithwaterandprepareformicroscopy.
True
trueorfalse:Thecorrectorderofanacid-faststainisprimarystaining, decolorizing,
counterstaining.Theacid-faststainingprocedurewouldbecategorizedasadifferentialstain.
clear
Ifmethylenebluewasomittedfromtheacid-faststainingprocedure,non-acid-fastcellswouldbe
______attheendofthestainingprocess.
yes
Wastheuseofethanolonthelabbenchusefulinreducingthenumberofbacteriapresent?
Cannedliquidslikejuiceorsodaarepreparedtobefreeofmicrobial contamination.
Whywastheliquidinthecanfoundtobefreeofmicrobes?
Theoutsideofthecanwouldbecoveredinmicrobes.
Whatwouldyouexpectiftheoutsideofthecanwassampledinstead?
Washingwithsoapandwaterdoesnotmakethehandsterile;itmerelyreducesthenumberofbacteria
present.
, Whywerebacteriapresentonthehandafterwashingwithsoapandwater?
Gram-negative organismsmightnotbevisible.
YouareGramstainingaknownsamplethatcontainsbothgram-positiveandgram-negative bacteria.
Afteryoucompletethestaining, yourealizethatyoudidnotperformthesafraninstep.Whichofthe
followingstatementswouldcorrectlydescribewhatyouwouldsee?
Gram-positiveorganismsmightincorrectlystainred.
YouareGramstainingaknownsamplethatcontainsbothgram-positiveandgram-negative bacteria.
Afteryoucompletethestaining, yourealizethatyouperformedthedecolorizer stepfor10minutes
insteadof10seconds!Whichofthefollowingstatementswouldcorrectlydescribe whatyouwould
see?
Gram-negative cellsGram-positivecells
YouareGramstainingaknownsamplethatcontainsbothgram-positiveandgram-negative bacteria.
Afteryoucompletethestaining, yourealizethatyoudidnotusethealcohol bottleatall.Whichcells
wouldappearpurple? Selectallthatapply.
smearstaining
Correctorderofstepsforsmearprepatation
Appropriatelylabel slide
Applybacteriatotheslideusingaseptictechnique
Airdrying
Heatfixation
Applystainingmethod
Asampleofpondwater,lookingforlivingbacterial activitysuchasobservingformotility
Basedonwhatyoulearnedinthissimulation, forwhichofthefollowingsampleswouldyouskiptheheat
fixationstep?
Clear(colorless)
Ifsafraninwasomittedfromthesporestain,thevegetativebacterialcellswouldappearincolor.
Correct OrderofStepsto PerformaSporeStain
Applymalachitegreenandasmall stripofpapercoveringtoapreparedsmear
Steamoverheatsource
Rinse
Applysafranintosmear
Rinseandblotdry
withcorrectanswers
YouareobservingStreptococcuspneumoniaeonaslide thathasbeenstainedusingthecapsular
stainingmethod.However,youdonotseecapsulessurroundingthecellsasyouexpected.Whatisa
likelyreasonforthis?
Theslidewasheatfixed,whichcanshrinkordestroycapsules.
Correct OrderofStepsto PerformaCapsuleStain
Applyprimarystain(indiainkornigrosin)toacleanslide.
Useinoculatinglooptoasepticallymixbacterial samplewithprimarystain.
Createathinsmearbydraggingacleanslide throughthesample.
Allowsampletothoroughlyairdry.
Applysecondarystain(crystalviolet)tosmear.
Rinsewithwaterandprepareformicroscopy.
True
trueorfalse:Thecorrectorderofanacid-faststainisprimarystaining, decolorizing,
counterstaining.Theacid-faststainingprocedurewouldbecategorizedasadifferentialstain.
clear
Ifmethylenebluewasomittedfromtheacid-faststainingprocedure,non-acid-fastcellswouldbe
______attheendofthestainingprocess.
yes
Wastheuseofethanolonthelabbenchusefulinreducingthenumberofbacteriapresent?
Cannedliquidslikejuiceorsodaarepreparedtobefreeofmicrobial contamination.
Whywastheliquidinthecanfoundtobefreeofmicrobes?
Theoutsideofthecanwouldbecoveredinmicrobes.
Whatwouldyouexpectiftheoutsideofthecanwassampledinstead?
Washingwithsoapandwaterdoesnotmakethehandsterile;itmerelyreducesthenumberofbacteria
present.
, Whywerebacteriapresentonthehandafterwashingwithsoapandwater?
Gram-negative organismsmightnotbevisible.
YouareGramstainingaknownsamplethatcontainsbothgram-positiveandgram-negative bacteria.
Afteryoucompletethestaining, yourealizethatyoudidnotperformthesafraninstep.Whichofthe
followingstatementswouldcorrectlydescribewhatyouwouldsee?
Gram-positiveorganismsmightincorrectlystainred.
YouareGramstainingaknownsamplethatcontainsbothgram-positiveandgram-negative bacteria.
Afteryoucompletethestaining, yourealizethatyouperformedthedecolorizer stepfor10minutes
insteadof10seconds!Whichofthefollowingstatementswouldcorrectlydescribe whatyouwould
see?
Gram-negative cellsGram-positivecells
YouareGramstainingaknownsamplethatcontainsbothgram-positiveandgram-negative bacteria.
Afteryoucompletethestaining, yourealizethatyoudidnotusethealcohol bottleatall.Whichcells
wouldappearpurple? Selectallthatapply.
smearstaining
Correctorderofstepsforsmearprepatation
Appropriatelylabel slide
Applybacteriatotheslideusingaseptictechnique
Airdrying
Heatfixation
Applystainingmethod
Asampleofpondwater,lookingforlivingbacterial activitysuchasobservingformotility
Basedonwhatyoulearnedinthissimulation, forwhichofthefollowingsampleswouldyouskiptheheat
fixationstep?
Clear(colorless)
Ifsafraninwasomittedfromthesporestain,thevegetativebacterialcellswouldappearincolor.
Correct OrderofStepsto PerformaSporeStain
Applymalachitegreenandasmall stripofpapercoveringtoapreparedsmear
Steamoverheatsource
Rinse
Applysafranintosmear
Rinseandblotdry
