TONB-DEPENDENT IRON SUPPLY IN SALMONELLA BY ALPHA-KETOACIDS AND ALPHA-HYDROXYACIDS

A range of structurally diverse alpha-ketoacids and alpha-hydroxyacids promoted the growth of isolates of Salmonella serovars S. typhinzurin m, S. enteritidis, S. agona, S. paratyphi and S. stanleycille in iron restricted conditions in the absence of functional siderophores. Growt h stimulation, observed both in cross-feeding tests on solid medium an d in liquid cultures, and uptake of Fe-55 in the presence of alpha-ket oisocaproic acid, were TonB dependent in S. typhimurium. In this respe ct the mechanism is distinct from a previously described Serratia marc escens system (sfuABC); the presence of the cloned sfuABC genes mediat ed tonB-independent uptake by S. typhimurium of iron complexed with al pha-ketoacids.