TRANSPORT OF MANNOSE BY AN INDUCIBLE PHOSPHOENOLPYRUVATE - FRUCTOSE PHOSPHOTRANSFERASE SYSTEM IN STREPTOCOCCUS-SALIVARIUS

Streptococcus salivarius transports mannose by a phosphoenolpyruvate:s ugar phosphotransferase system (PTS) which consists of a membrane Enzy me II and two forms of Enzyme III (IIIMan) With molecular masses of 38 .9 kDa (IIIHMan) and 35.2 kDa (IIILMan) respectively. Using a pseudore vertant (strain 57P) isolated from a IIILMan-deficient spontaneous mut ant unable to grow on mannose. we demonstrated that S. salivarius coul d also transport mannose by an inducible fructose PTS. This PTS phorph orylated fructose at the C-1 position with a high affinity (10 mu M) a nd mannose at the C-6 position with a low affinity (200 mu M). Derepre ssion of this system in some IIILMan-deficient mutants would explain t heir ability to grow on mannose.