g Consider a culture medium such as mannitol salt agar (MSA) on which only gram-positive organisms such as Staphylococcus sp. Colonies can grow due to an elevated NaCl level. A yellow halo surrounds some colonies on the medium, indicating they are able to ferment the mannitol sugar, decreasing the pH and changing the color of a pH indicator chemical. This type of medium would be referred to as:

Selective and differential medium

Explanation:

The type of medium described in the illustration would be referred to as a selective and differential medium.

There are basically 6 types of growth media for microbes based on the chemical composition of the medium;

Enrich media: media that are enriched by substances such as blood, egg, etc. E.g. blood agar.Basal media: media that can be used to culture organisms without the addition of any substance. E.g nutrient agar.Selective media: media that selectively favors the growth of one organism or a group of organisms over the others due to its contents. E.g. Mannitol Salt Agar, McConkey agar, etc.Differential media: media that has the potential to change color with respect to a particular organism. E.g Mannitol salt agar.Transport media: media that are used to transport organisms due to the fact that they cannot be cultured where they are collected. E.g Stuart mediumStorage media: media used to store organisms for future uses. E.g saline medium

Mannitol salt agar has the capacity to favor the growth of a particular organism by indicating a color change. Hence, it is referred to as a selective and deferential medium.