When a Staphylococci species ferments mannitol on Mannitol Salt Agar,

A. the Staphylococci cells turn yellow

B. the Staphylococci colonies turn yellow

C. the media around the Staphylococci colonies turns yellow

C. the media around the Staphylococci colonies turns yellow

Explanation:

An example of a selective and differential medium is the Mannitol Salt Agar (MSA).

The acidic byproduct of the fermentation of mannitol, causes the phenol red component in the agar to turn yellow.

Staphylococcus aureus though pathogenic will ferment mannitol.

The Answer is C

Explanation:

Mannitol salt agar is a selective, differential growth medium used for the culture of staphylococcus bacteria capable of fermenting mannitol which is the principal sugar source. The medium contains mannitol as the sugar source and (7.5 - 10%) sodium chloride which inhibits the growth of most other bacteria, phenol red; an indicator for detecting pH change produced due to mannitol fermentation. The fermentation of mannitol by the bacteria causes the production of an acidic byproduct changing the colour of the medium to change from pink/red to yellow.