Why will gram positive cells stain gram negative?

Answer by  labgirl (333)

Some gram positive cells easily lose dye. Overgrown cultures of gram positive cells may appear gram negative. Tests will be reliable if you know your strains and culture techniques well.

Answer by  HH (404)

This occurs when the cells are aged and therefore the Gram-positive wall is degraded and thus thinner. Remember it keeps the stain in. Do the stain on a fresh culture.

Answer by  Anonymous

If you overheat them during heat fixing and thereby break up the cell wall