Question

Consider a culture medium on which only gram-positive organisms such as Staphylococcus aureus colonies can grow due to an elevated NaCl level. A yellow halo surrounds the growth, indicating the bacterium fermented a sugar in the medium, decreasing the pH as a result and changing the color of a pH indicator chemical. This type of medium would be referred to as a(n):______
a) enrichment culture.
b) differential and enrichment culture.
c) selective and differential medium.
d) selective median.

Answer 1

Answer:

C) Selective and differential medium.

Explanation:

Selective Medium:

A media contains specific ingredients which are required to promote the growth of microorganism and inhibit the other microorganisms to grow is called selective medium.

Differential Medium:

A media contains specific ingredients which differentiate the same group organisms or closely related organisms is called differential medium.

NaCl is used in media to promote the growth of Staphylococcus aureus and inhibit the growth of other gram positive and negative bacteria.

A yellow halo color shows the bacterial fermentation of sugar which will distinguish Staphylococcus aureus with other strains.

So, it will be selective and differential medium which will allow to grow Staphylococcus aureus and differentiate with other bacteria.