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Learn About Microbiology

What is the Difference Between Gram Positive and Gram Negative Bacteria?

Written by Jason Williams, B.S.

The main difference between gram negative and gram positive bacteria has to do with the arrangement of the outer portions of the cell.

The two illustrations that follow represent cross-sections of the cell wall and cell membrane of gram positive bacteria and gram negative bacteria, respectively.

In general, gram positive bacteria tend to persist in dry environments better and are often found on places like the skin and in dust. Gram negative bacteria, on the other hand, are killed more quickly by drying but thrive in aqueous environments. Gram negative bacteria also tend to grow better in the presence of toxic chemicals (such as chlorine), a feat thought to be enabled by their two cell membranes.

Gram Positive Bacterium

Gram Negative Bacterium