What metabolic process does the Citrate test assess?

The Citrate test specifically assesses the ability of an organism to utilize citrate as its sole carbon source. In environments where organic compounds are limited, certain bacteria can metabolize citrate, which is commonly found in the Krebs cycle, to generate energy. The test utilizes a medium containing citrate and is typically formulated with a pH indicator that changes color in response to changes in pH caused by the metabolism of citrate. When citrate is utilized, alkaline byproducts are produced, leading to an increase in pH and a resulting color change, which indicates a positive result.

This test is particularly useful for differentiating among members of the Enterobacteriaceae family, as only certain species possess the necessary enzymes, such as citrate permease, to transport citrate into the cell and utilize it effectively. Thus, the Citrate test is crucial for the identification and classification of bacteria based on their metabolic capabilities.