text: what are the disadvantages of gram negative and gram positive bacteria?   the positives can be stained, the others can't. the staining possibility is an advantage for further research under a microscope. there is even more to it because gram-positive bacteria belong to a separate phylum different from the gram negatives.  the stain becomes possible by a high amount of peptidoglycan in the cell wall, which typically, but not always lacks the secondary membrane and lipopolysaccharide layer found in gram-negative bacteria