If you grow two species of bacteria on mannitol salt agar to determine which can ferment mannitol, and you know both species can grow on the medium, which type of medium is the agar? (A) differential (B) selective (C) both a differential medium and a selective medium (D) neither a differential medium nor a selective medium

Mannitol salt agar is a fun and fascinating medium! It’s designed with a high salt concentration that most bacteria can't tolerate, which gives it its selective nature. Only bacteria that are salt-tolerant can grow on it, like Staphylococcus species. And guess what? It also differentiates between whether those bacteria can ferment mannitol by changing color when fermentation occurs – hello, phenol red indicator! In practice, this makes mannitol salt agar incredibly useful for lab settings, especially in identifying Staphylococcus aureus. By observing whether growth occurs and if there's a color change from red to yellow, you can quickly tell which bacteria can ferment mannitol and which can't. It's like a two-for-one special in the bacterial world!