Bacteria are classified as gram positive or negative depending on whether or not they take up gram stain. The bacteria cell wall is unusual in its chemical construction .It has a strong layer of sugar polymer, cross-linked by amino acid and called *PEPTIDOGLYCAN*.
The bacteria cell wall that has a much of peptidoglycan stains *blue, and termed Gram positive*,while the *gram negative have less peptidoglycan and stained pink to red*. Example of Gram positive bacteria are Clostridium tetani, wound infecting Staphylococcus aureus(spherical),Tuberculosis-causing actinomycetes -Mycobacterium tuberculosis. Examples of Gram negative bacteria are Syphilis causing Treponema pallidum(spiral),Escherichia coli(rod), gonorrhea causing Neisseria gonorrhoeae(spherical),and Cyanobacteria.
