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 (IIIHMan) and 35.2 kDa (IIILMan) respectively. Using a pseudorevertant (strain 57P) isolated from a IIILMan-deficient spontaneous mutant unable to grow on mannose. we demonstrated that S. salivarius could also transport mannose by an inducible fructose PTS. This PTS phorphorylated fructose at the C-1 position with a high affinity (10 mu M) and mannose at the C-6 position with a low affinity (200 mu M). Derepression of this system in some IIILMan-deficient mutants would explain their ability to grow on mannose.