VJ agar, which is both a selective and differential media, used to specifically identify Staphylococcus aureus, which is a potential human pathogen, with Beta hemolysis ability and the cause of staph infections. this media specifically selects for the growth of staphylococci, and differentiates for mannitol fermentors (via pH indicator, which changes the media color from orange to yellow indicating mannitol was fermented and an acid byproduct was produced). the media also contains the compound tellulrite, which S. aureus can reduce to produce a black byproduct causing the bacteria to turn black as seen above, which means the bacteria also possesses the enzyme coagulase. the VJ agar is one of the main tests used to identify pathogenic strains of S. aureus.