1. Gram Staining Laboratory Report
Nailah Mapson #32
September 28, 2015
Magnet Foundations
Academy of Research and Medical Sciences

2. Lab #4: Gram-Staining
Nailah Mapson
September 28, 2015
Block 4
The purpose of thislab wasto compare freshyogurtto2-day yogurtby analyzingthe gram-
stainedbacteriaof both. Gram-Stainingisusuallyamethodof identifyingabacterial organism, butin
thislabthe type of bacteriawas alreadyknown,soitwasusedto differentiate betweenfreshyogurtand
2-day oldyogurtby comparingthe Gram-stainedbacteria.There are twotypesof Gram-stained
bacteria,Gram-PositiveandGram-negative.Gram-Positivebacteriaare staineddark blue orviolet bythe
crystal violetstain,theyare able toretainthiscolorbecause of the highamount of peptidoglycanin
theircell wall.Gram-Negativeisunable toretainthe colorbecause of the manylayers of the bacteria,so
it will take upthe counterstain,safranin.
Gram + Gram -
Refrigerated Yogurt X
2- day Unrefrigerated Yogurt X X
In the processof thisexperiment,onlyvisual datacouldbe gathered. Inday1, all of the bacteria
was stained Gram-Positive,butjustlookingatthe bacteriawas notthe mostaccurate wayto gather the
informationbecause there isachance that the resultswere wrong.OnDay2, there was a 50/50 division
of bothGram + and Gram- , thisjustbeinga visual estimation.Itishighlylikelythatthese resultscould
be wrong because the humaneye isnotthe most accurate instrumentintermsof everything. There are
manyfactors that couldchange the resultof the experiment,suchasbeingcolor-blindoronlybeingable

3. to see certaincolors.Color-blindnessisthe difficultyorinabilitytodistinguishcertaincolorscausedby
problemswiththe color-sensingpigmentsinthe eye.Inanycase,thatsomeone hadthe eye problem
thiscouldaffectthe resultsbysayingthat youcan’t see the violetthatGram-Positive issupposedtobe,
or that it wasimpossibletosee the pinkthatGram-Negative issupposedtobe.Theycouldruinthe
resultsbecause the group couldnotcome to a conclusionaboutwhatgroupthe bacteriafell under.
Therefore,if theywere unable of seeingthe colors,the conclusionwouldbe theyhadtositout,but the
numberof people actuallyseeingthe colorswouldbe lowerandthenthe accuracy evenlower.
Yogurt staysfreshunrefrigerated foranabnormally longtime.Leftoutinthe sun,the top of the
yogurtwas the onlypart to developGram-Negative bacteria. There are caseswere groupsonthe 2nd
day
of yogurtstainingwiththe 2-dayunrefrigeratedyogurt,didnothave anyGram-Negativebacteria,
therefore theyhadtogeta 2nd
sample of yogurtto gram-stain.The reasonforthe needtodo itagain is
because those groupsreceivedyogurtfromthe middle tobottomof the yogurtcontainer. Itseems
because of the acidityof yogurt itdoesn’tspoil aseasilyasmilkorsour cream.