sigma54-Mediated control of the mannose phosphotransferase sytem in Lactobacillus plantarum impacts on carbohydrate metabolism.

Sigma factors direct specific binding of the bacterial RNA polymerase to the promoter. Here we present the elucidation of the sigma(54 ) regulon in Lactobacillus plantarum. A sequence-based regulon prediction of sigma(54)-dependent promoters revealed an operon encoding a mannose phosphotransferase system (PTS) as the best candidate for sigma(54)-mediated control. A sigma (54) (rpoN) mutant derivative did not grow on mannose, confirming this prediction. Additional mutational analyses established the presence of one functional mannose PTS in L. plantarum, the expression of which is controlled by sigma(54) in concert with the sigma(54)-activator ManR. Genome-wide transcription comparison of the wild-type and the rpoN-deletion strain revealed nine upregulated genes in the wild-type, including the genes of the mannose PTS, and 21 upregulated genes in the rpoN mutant. The sigma(54)-controlled mannose PTS was shown also to transport glucose in L. plantarum wild-type cells, and its presence causes a lag phase when cultures are transferred from glucose- to galactose-containing media. The mannose PTS appeared to drain phosphoenolpyruvate (PEP) pools in resting cells, since no PEP could be detected in resting wild-type cells, while mannose PTS mutant derivatives contained 1-3 muM PEP (mg protein)(-1 ). Our data provide new insight into the role of sigma( 54) in L. plantarum and possibly other Gram-positive bacteria in the control of expression of an important glucose transporter that contributes to glucose-mediated catabolite control via modulation of the PEP pool.