Microbiology McGraw Hill Lab Exam with correct answers

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