Bacteria with thick peptidoglycan are called gram positive. If the peptidoglycan layer is thin, it's classified as gram negative. A gram-positive bacillus doesn't have an outer cell wall beyond ...

Gram-positive bacteria show blue or purple after Gram-staining in a laboratory test. They have thick cell walls. Gram-negative bacteria show pink or red on staining and have thin walls.

Most species of bacteria can be broadly divided into two groups, known as gram-positive and gram-negative. These categories reflect big differences in the microbes' biology, and they also dictate ...