difference between gram positive and gram negative bacteria pdf by easybiologyclass
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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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