Types of bacteri on basis of bacterial staining

Bacterial staining       

                       Bacteria can be differentiated into two as gram positive and gram negative .This was first done by Danish Physician named Christian Gram in 1884.

                In this process a smear of bacteria is heated and then violet dye is added to stain it for thirty seconds. Then it is rinsed and iodine solution is added. When iodine is added it is turned to deep blue. The iodised smear is treated with 95% alcohol. This decolourises some of the bacteria and then saffrin is added. When saffrin is added the decolourised bacteria change to red. These red bacteria are called  Gram negative bacteria and the non decolourised bacteria change to purple and are called Gram positive.

  Smear of bacteria---heated—violet dye added—rinsed—added iodine solution—turn smear to red – treated with 95% alcohol – decolourises some of bacteria – added sffrin – change decolourised bacteria to red and non decolourised  remain purple—red called Gram negative – purple called Gram positive.