Glutamate excretion mechanism in Corynebacterium glutamicum: Triggering by biotin starvation or by surfactant addition

Abstract

Cells of an industrial strain of the L-glutamate producer Corynebacterium glutamicum grown in biotin-starvation conditions lost 30% of their membrane phospholipids. This was accompanied by a progressive decrease in the rate of accumulation of glutamate and of the intracellular glutamate accumulated at the plateau. Addition of an acylated surfactant to growing cultures of the same strain also induced a progressive loss of glutamate uptake, without changing the K(T) of the process. The surfactant-treated cells almost completely excreted the labelled glutamate loaded during a preincubation. These results, together with those obtained previously, allow us to propose that glutamate excretion is mediated by a glutamate permease, after uncoupling of this uptake system resulting from a marked loss of membrane phospholipids. This loss of phospholipids can be induced either by biotin starvation or by addition of an acylated surfactant to growing cells.