OF (Oxidative Fermentative) Basal Medium is used for the determination of the oxidative and fermentative metabolism of specific carbohydrates by Gram-negative bacteria. Casein Enzymatic Hydrolysate provides nitrogenous sources. The fermentable carbohydrate is added separately. Dipotassium Phosphate serves as pH buffer. Sodium Chloride maintains the osmotic balance. Bromothymol Blue is the pH indicator. The low concentration of Agar permits the detection of motility and aids in the even distribution of the acids generated by the bacterial metabolism. Non-motile organisms grow along the line of inoculation, while motile organisms spread out of this zone.