Question

On what basis gram positive and gram-negative bacteria

Answer 1

by using Gram staining method one can determine the bacteria as positive or negative.
in this process the bacterial culture is stained with Crystal Violet and Iodine is added into it for fixing the stain thus leading to the formation of Crystal Violet Iodine complex then the stain is washed with alcohol
the bacteria which hold the purple colour are known as Gram Positive Bacteria while the one which do not hold the colour of stain is known as Gram Negative bacteria