Define Citrate Utilization Test - imvic test?

Several microorganisms have the ability to make use of citrate as the sole source of carbon and energy. This ability relies on the presence of citrate permease and citrase in the organism. Citrate permease makes easy the transport of citrate in the cell while citrase acts on citrate to produce oxaloacetic acid and acetate as pointed out in the reaction.

Citrate utilization through microorganisms can be detected by using Simmons citrate medium that consists of sodium citrate as the sole carbon source and bromothymol blue like pH indicator. When citrate in the medium is utilized by microorganisms, resulting CO₂ reacts with sodium and water to form sodium carbonate. This alterations the pH of the medium to alkaline and its colour from green to deep prussian blue. Bromothymol blue is green while acidic (pH 6.8 and below) and blue while alkaline (pH 7.6 and higher).