Description Nutrient-TTC Agar is a general purpose (relatively non-selective) medium, which will support the growth of a wide variety of organisms. Suitable for cultivation of both aerobes and anaerobes. Aerobic coliform bacteria can be detected by their ability to reduce the TTC dye to a red-colored formozan dye. Bacterial colonies appear as red dots on an otherwise yellow medium. MacConkey Agar is both selective and differential. It is used to differentiate between Gram negative bacteria while inhibiting the growth of most Gram positive bacteria. The medium also differentiates between lactose-fermenting coliforms (Lac ( )) and lactose non-fermenters (Lac (-)), which include potential pathogens. Nutrient-TTC (NUT), Tryptic Soy (TSA), and MacConkey (MAC) agars can all be used for marine waters. Testing is essentially identical as for freshwater.
