TonB-dependent iron supply inSalmonellaby α-ketoacids and α-hydroxyacids

Abstract
A range of structurally diverse α-ketoacids and α-hydroxyacids promoted the growth of isolates of Salmonella serovars S. typhimurium, S. enteritidis, S. agona, S. paratyphi and S. Stanleyville in iron restricted conditions in the absence of functional siderophores. Growth stimulation, observed both in cross-feeding tests on solid medium and in liquid cultures, and uptake of 55Fe in the presence of α-ketoisocaproic acid, were TonB dependent in S. typhimurium. In this respect the mechanism is distinct from a previously described Serratia marcescens system (sfuABC); the presence of the cloned sfuABC genes mediated tonB-independent uptake by S. typhimurium of iron complexed with α-ketoacids.