The oxidase test is used to determine if a bacterium is capable of making cytochrome c oxidases. It uses disks impregnated with a reagent such as N,N,N'N-tetramethyl-p-phenylenediamine or N,N-dimethyl-p-phenylenediamine, which is also a redox indicator. When it oxidizes, the reagent is a dark blue to maroon color. When reduced, they are both colorless. cytochrome oxidase or indophenol oxidase is a oxidase positive bacteria's main oxidase. An iron containing hemoprotein is what it is. The compounds came from the donor. It is to electron acceptors. Usually there is some form of oxygen. The colored compound indophenol blue is formed by the oxidation of the test reagent, which acts as an artificial electron donor for the enzyme oxidase. The cytochrome system is usually only present in aerobic organisms. Oxygen is capable of being used as the terminal electron acceptor. The end product of this metabolism is either water or hydrogen peroxide. The triple sugar iron agar is a differential medium that contains lactose, sucrose, a small amount of glucose, dextrose, ferrous sulfate and the pH indicator phenol red. It is used to differentiate enterics based on their ability to ferment and reduce sulfur. If an organisms can ferment any of the three sugars present in the medium, the medium will turn yellow. The small amount of dextrose in the medium can be used by the organisms within the first ten hours of being in the medium. The reaction is produced after that time. The slant and medium in the aerobic area turn red because of acid reverting in the aerobic area. The alkaline conditions are indicated by. The butt and other areas of the slants will remain yellow even though they will not return to an alkaline state.