True or False: Non-fermenters such as proteus sp. on a MAC plate appear colourless or transparent.

The assertion is accurate; non-fermenters, like Proteus species, exhibit a colorless or transparent appearance on a MacConkey (MAC) agar plate. This media is selective for gram-negative bacteria and differentiates them based on their ability to ferment lactose. Non-fermenters do not break down lactose, hence they do not produce acid, leading to a lack of color change in the agar surrounding their colonies. Typically, lactose fermenters produce pink colonies because they generate acid that reacts with the pH indicator in the MAC agar. On the other hand, as non-fermenters do not alter the pH of the medium, their colonies remain colorless or transparent. This characteristic supports the identification and differentiation of bacterial species in a clinical laboratory setting.