Citrobacter

Citrobacter is a genus of Gram-negative coliform bacteria in the Enterobacteriaceae family.

The species C. amalonaticus, C. koseri, and C. freundii can use citrate as a sole carbon source. Citrobacter species are differentiated by their ability to convert tryptophan to indole, ferment lactose (C. koseri is a non-lactose fermentor), and use malonate.