Transport of mannose by an inducible phosphoenolpyruvate:fructose phosphotransferase system in Streptococcus salivarius.

Streptococcus salivarius transports mannose by a phosphoenolpyruvate:sugar phosphotransferase system (PTS) which consists of a membrane Enzyme II and two forms of Enzyme III (IIIMan) with molecular masses of 38.9 kDa (IIIManH) and 35.2 kDa (IIIManL) respectively. Using a pseudorevertant (strain 57P) isolated from a IIIManL-deficient spontaneous mutant unable to grow on mannose, we demonstrated that S. salivarius could also transport mannose by an inducible fructose PTS. This PTS phosphorylated fructose at the C-1 position with a high affinity (10 microM) and mannose at the C-6 position with a low affinity (200 microM). Derepression of this system in some IIIManL-deficient mutants would explain their ability to grow on mannose.