A positive citrate utilization test indicates that an Enterobacteriaceae species can use what as its sole carbon source?

A positive citrate utilization test indicates that an Enterobacteriaceae species can use what as its sole carbon source?

• A. Glucose
• B. Fructose
• C. Sucrose
• D. Citrate

Answer: (D)

A positive citrate utilization test indicates that the Enterobacteriaceae species can use citrate as its sole carbon source. This test specifically assesses the organism's ability to transport and metabolize citrate in the absence of fermentable carbohydrates like glucose, fructose, or sucrose. When citrate is utilized, the organism converts it to carbon dioxide and sodium bicarbonate, leading to an alkaline reaction that changes the color of the medium, commonly indicated by a color change in the pH indicator present in the test medium. Citrate is not only a key component of the citric acid cycle but also serves as a unique carbon source that some bacteria can utilize when other carbohydrates are unavailable. This ability helps differentiate certain Enterobacteriaceae, such as those within the Citrobacter and Enterobacter genera, from those that are unable to utilize citrate. This metabolic capability is significant in microbiological identification and classification within the family.

A positive citrate utilization test indicates that the Enterobacteriaceae species can use citrate as its sole carbon source. This test specifically assesses the organism's ability to transport and metabolize citrate in the absence of fermentable carbohydrates like glucose, fructose, or sucrose. When citrate is utilized, the organism converts it to carbon dioxide and sodium bicarbonate, leading to an alkaline reaction that changes the color of the medium, commonly indicated by a color change in the pH indicator present in the test medium.

Citrate is not only a key component of the citric acid cycle but also serves as a unique carbon source that some bacteria can utilize when other carbohydrates are unavailable. This ability helps differentiate certain Enterobacteriaceae, such as those within the Citrobacter and Enterobacter genera, from those that are unable to utilize citrate. This metabolic capability is significant in microbiological identification and classification within the family.