Question

what are gram positive and gram negative bacteria?

Answer 1

Gram-positive bacteria take up the crystal violet stain used in the test, and then appear to be purple-coloured when seen through a microscope. This is because the thick peptidoglycan layer in the bacterial cell wallretains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test.

Gram-negative bacteria cannot retain the violet stain after the decolorization step; alcohol used in this stage degrades the outer membrane of Gram-negative cells, making the cell wall more porous and incapable of retaining the crystal violet stain. Their peptidoglycan layer is much thinner and sandwiched between an inner cell membrane and a bacterial outer membrane, causing them to take . 

Answer 2

Gram positive bacteria are the bacteria that gives a positive result in the gram stain test which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall
And gram negative bacteria are a group of bacteria that do not retain the crystal violet stain used in the gram staining method of bacterial differentiation.