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GramPositiveBacteriaVsGramNegativeBacteria(SimilaritiesandDifferencebetweenGramPositiveandGramNegativeBacteria)

WhatisGramsstaining?

ChristianGram,aDanishPhysician in1884developedastainingtechniquetodistinguishtwo types of bacteria. The two categories of bacteria based on gram staining are GrampositivebacteriaandGramnegativebacteria.Bacteriaarefirststainedwithcrystalvioletor gentian violet. All bacterial cells will stain blue or purple colour with crystal violetsolution.Thenthebacterialcellsaretreatedwithiodinesolution(Lugol’siodine)solutionandwashedwithalcohol (de‐staining solution). Thosebacteriawhich retain theblueorpurplecolourofcrystalvioletarecalledGrampositivebacteriaandthosebacteriawhichloose the colour of crystal violet after washing with de‐staining solution is called GramNegative bacteria. Gram negative bacteria are later stained with safranin or fuchsin forobservation undermicroscope. Gram negative bacteria after safranin or fuchsin stainingcolour red or pink colour. Gram staining differentiates bacteria by the chemical andphysicalpropertiesof their cellwallsbydetecting thepropertiesofpeptidoglycan.Gramstainingmethod is useful in differentiatingmajority of bacterial species into two broadcategories. Even though all bacterial species cannot be differentiated based on gramstaining technique, this method has immense application in clinical diagnostics andbiologicalresearches.

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SimilaritiesbetweenGramPositiveandGramNegativeBacteria

Botharebacterialcells Bothgroupsareprokaryotic Bothlackmembraneboundedorganelles BothgroupshavecovalentlyclosedcircularDNAasthegeneticmaterial Bothgroupscontainextra‐chromosomalgeneticmaterials(plasmids) Bothgroupsposescapsule Inbothgroups,cellwallismadeupofpeptidoglycan In both groups, cytoplasm is surrounded by lipid bilayer with many membrane

spanningproteins. Both gram‐positive and gram‐negative bacteria commonly have a surface layer

calledanS‐layer Both groups of bacteria undergo genetic recombination through transformation,

transductionandconjugation Bothgroupsundergobinaryfissionasamodeofasexualreproduction Bothgroupscontainmanyflagellatedandnon‐flagellatedspecies Both gram positive and gram negative bacteria are inhibited by antibiotics (their

sensitivityvaries) Bothgroupsincludesflagellated(motile)andnon‐flagellated(non‐motile)forms

DifferencebetweenGramPositiveBacteriaandGramNegativeBacteria

Sl.No. GramPositiveBacteria GramNegativebacteria

1AppearsasdarkvioletorpurplecolouredundermicroscopeafterGramstaining

AppearsaspinkorredcolouredafterGramstaining

2Retainthecolourofcrystalvioletafterwashingwithalcohol(de‐stainingsolution)

Colourofcrystalvioletwillnotberetainedafterwashingwithde‐stainingsolutionwww.ea

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3Examples:Bacillussubtilis,Streptococcus,Lactobacillus,Leuconostoc,Clostridium

Examples:Escherichiacoli,Rhizobium,Vibrio,Acetobacter

4Cellwallsinglelayered,straightandeven

Cellwalltwolayeredanduneven(wavy)

5 Cellwallisveryrigidandlesselastic Cellwallislessrigidandmoreelastic

6Therigidityofcellwallisduetothehighproportionofpeptidoglycans(80%)

Theelasticityofcellwallisduetothelessamountofpeptidoglycan(2–12%)

7Thicknessofcellwallvariesfrom15‐20nm,sometimesupto80nm

Thicknessofcellwallvariesfrom7.5to12nm

8 Muramicacidcontentofcellwallismore,16–20%ofdryweight

Muramiccontentofcellwallisless,2–5%ofdryweight

9 Cellwallisresistanttoalkalisandinsolublein1%KOHsolution

Cellwallissensitivetoalkalisandsolublein1%KOHsolution

10Cellishighlyresistantofphysicaldisruptions

Cellishighlysusceptibletophysicaldisruptions

11 S‐layerisattachedtothepeptidoglycanlayer

S‐layerisattachedtotheoutermembrane

12 Teichoicacidpresentinthecellwall Teichoicacidabsentinthecellwall

13 Periplasmicspaceabsent Periplasmicspacepresent

14 Outermembraneabsent Outermembranepresent

15 Lipidcontentverylow(1‐4%) Lipidcontentveryhigh(11‐22%)

16Porins(proteinaceousmembranechannels)areabsent Porinsarepresent

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17 Lipopolysaccharidesusuallyabsent Lipopolysaccharidespresent

18 Mesosomesaremoreprominent Mesosomesarelessprominent

19 Produceendosporessporesduringunfavourableconditions Usuallydonotproduceendospores

20 Flagellawith2ringsinthebasalbody Flagellawithfourringsinthebasalbody

21 Usuallyproduceexotoxins Usuallyproduceendotoxins

22 Grampositivebacteriaaremoresusceptibletoantibiotics

Gramnegativebacteriaaremoreresistanttoantibiotics

23 Canbekilledbyvancomycinantibiotic Cannotbekilledbyvancomycinantibiotic

24 Showshighresistancetosodiumazidesolution

Showslowresistancetosodiumazidesolution

25 Cellsshowshighsusceptibilitytowardspenicillinsandsulfonamideantibiotics

Cellsshowslowsusceptibilitytowardspenicillinsandsulfonamideantibiotics

26Cellsshowlowsusceptibilitytowardsstreptomycin,chloramphenicolandtetracyclines

Cellsshowshighsusceptibilitytowardsstreptomycin,chloramphenicolandtetracyclines

27Cellwallishighlysusceptibletodegradationbylysozymeenzyme

Cellwallislesssusceptibletodegradationbylysozymeenzyme

28 Showshightolerancetowardsdryness Showslowtolerancetowardsdryness

29 Magnetosomesusuallyabsent Magnetosomessometimespresent

30Veryfewarepathogenictohumanandotheranimals

Mostofthemarepathogenictohumanandotheranimals

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Violetstainedgram‐positivecocciandpinkstainedgram‐negativerod‐shapedbacteria(Imagesource:Wikipedia)

CellWallOrganizationofGramPositiveandGramNegativeBacteria

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