From class 8 ,we have been studying about gram positive and gram negative bacteria and the color they produced on staining but we have hardly tried to find out the underlying reasons for the same. Let me reveal it...
actually there are 2 types of staining-
1.simple staining (only one type of stain is used) and 2.differential staining (more than 2 types of stain are used)
In simple staining :
we know that the cell wall of bacteria has negative charge due to the presence of phospholipid .So if we use acidic dye (acidic dye has negative charge as for e.g NEGROSIN), we have to stain the slide not the bacteria. Similarly if we want to use basic dye(which is positive as for e.g METHYLENE BLUE) then we can stain the bacteria itself not the back ground.
GRAM STAINING:
This Stain is composed of 1)CRYSTAL VIOLET 2)GRAHMS IODINE 3)ALCOHOL 4)SAFRANINE
Here (1) is the primary stain,(2) is the MORDANT(which helps in staining by increasing the affinity) ,(3)is the decoloriser and (4) is the secondary stain or counter stain.all these chemicals are added one by one after the fixation process (when we take the sample microbe in a slide and dry it and heat in flame so to evaporate the extra water content of cell)
when we add chemical (1) and (2) there is a formation of CRYSTAL VIOLET GRAM IODINE COMPLEX .
Now in case of GRAMS NEGETIVE BACTERIA when we add decoloriser i.e chemical(3) there is removal of the above mentioned complex and in this when we add chemical (4) we get PINK COLOR which is actually the color of SAFRANINE.
Similarily in case of GRAM POSITIVE BACTERIA when we add chemical (3) there is no removal of the above mentioned complex and so we do not get the effect of chemical (4) but we get the colour of CRYSTAL VIOLET which is of BLUE color.
So GRAM POSITIVE BACTERIA gives BLUE color and GRAM NEGATIVE BACTERIA gives PINK color.
Now all this occurs due to the difference in composition of the cellwall of those bacterias,In GRAM +VE it has a thick layer of PEPTIDOGLYCAN and in case of GRAM -VE it has a very thin layer of PEPTIDOGLYCAN.These composition made all the difference.
e.g of GRAM +ve BACTERIA ARE STAPHYLOCOCCUS AND STREPTOCOCCUS
e.g ofGRAM -VE BACTERIA ARE CYANOBACTERIA AND SPIROCHETES.
THANK YOU
actually there are 2 types of staining-
1.simple staining (only one type of stain is used) and 2.differential staining (more than 2 types of stain are used)
In simple staining :
we know that the cell wall of bacteria has negative charge due to the presence of phospholipid .So if we use acidic dye (acidic dye has negative charge as for e.g NEGROSIN), we have to stain the slide not the bacteria. Similarly if we want to use basic dye(which is positive as for e.g METHYLENE BLUE) then we can stain the bacteria itself not the back ground.
GRAM STAINING:
This Stain is composed of 1)CRYSTAL VIOLET 2)GRAHMS IODINE 3)ALCOHOL 4)SAFRANINE
Here (1) is the primary stain,(2) is the MORDANT(which helps in staining by increasing the affinity) ,(3)is the decoloriser and (4) is the secondary stain or counter stain.all these chemicals are added one by one after the fixation process (when we take the sample microbe in a slide and dry it and heat in flame so to evaporate the extra water content of cell)
when we add chemical (1) and (2) there is a formation of CRYSTAL VIOLET GRAM IODINE COMPLEX .
Now in case of GRAMS NEGETIVE BACTERIA when we add decoloriser i.e chemical(3) there is removal of the above mentioned complex and in this when we add chemical (4) we get PINK COLOR which is actually the color of SAFRANINE.
Similarily in case of GRAM POSITIVE BACTERIA when we add chemical (3) there is no removal of the above mentioned complex and so we do not get the effect of chemical (4) but we get the colour of CRYSTAL VIOLET which is of BLUE color.
So GRAM POSITIVE BACTERIA gives BLUE color and GRAM NEGATIVE BACTERIA gives PINK color.
Now all this occurs due to the difference in composition of the cellwall of those bacterias,In GRAM +VE it has a thick layer of PEPTIDOGLYCAN and in case of GRAM -VE it has a very thin layer of PEPTIDOGLYCAN.These composition made all the difference.
e.g of GRAM +ve BACTERIA ARE STAPHYLOCOCCUS AND STREPTOCOCCUS
e.g ofGRAM -VE BACTERIA ARE CYANOBACTERIA AND SPIROCHETES.
THANK YOU
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ReplyDeleteThank you once again blog admin.