gram positive bacteria that can grow on macconkey agar
MacConkey agar By utilizing the lactose available in the medium, Lac+ bacteria such as Escherichia coli, Enterobacter and Klebsiella will produce acid, which lowers the pH of the agar below 6.8 and results in the appearance of pink colonies. The bile salts precipitate in the immediate neighbourhood of the colony, causing the medium surrounding the colony to become hazy.[4][5]
Corynebacterium The principal features of the Corynebacterium genus were described by Collins and Cummins in 1986.[6] They are gram-positive, catalase-positive, nonspore-forming, nonmotile, rod-shaped bacteria that are straight or slightly curved.[7] Metachromatic granules are usually present representing stored phosphate regions. Their size falls between 2 and 6 μms in length and 0.5 μm in diameter. The bacteria group together in a characteristic way, which has been described as the form of a "V", "palisades", or "Chinese letters". They may also appear elliptical. They are aerobic or facultatively anaerobic, chemoorganotrophs. They are pleomorphic through their lifecycles, they occur in various lengths, and they frequently have thickenings at either end, depending on the surrounding conditions.[8]