Bacteria are pathogenic microorganisms causing a number of diseases in humans from light to life threatening conditions. For proper treatment of patients infected with these diseases require proper diagnosis of diseases causing bacterial agent. As the bacteria are divided into two main as Gram Positive and Gram Negative Bacteria. Both type of bacteria exhibit a number of inherited biochemical properties by which we can differentiate, can check there presence and absence, can check their gram negative and gram positive nature. Therefore, the present review is focused to describe different biochemical tests in one article.