Question

What are Gram-positive and Gram-negative bacteria, and why do some antibiotics work on one type but not the other?

Answer 1

There are many ways of classifying bacteria. One method is based on the cell membrane.

We have:

Bacteria with thick peptidoglycan layer

Bacteria with thin peptidoglycan layer

This two types of bacteria can be distinguished by Gram staining:

Bacteria with thick peptidoglycan layer---->gram positive (purple or blue in color)

Bacteria with thin peptidoglycan layer ----->gram negative (pink or red in color)

All drugs that act on the outer membrane will be useful to eliminate an infection by gram negative bacteria. But they would not work for gram positives since they lack this layer.