[Phosphoenolpyruvate:hexose phosphotransferase systems in Lactobacillus species]

The substrate range of phosphoenolpyruvate:hexose phosphotransferase systems (hexose-PTSs) in Lactobacillus casei subsp. casei LAC3 and L. acidophilus LAC5 was examined. Strain LAC3 demonstrated PTS activities for glucose (Glc), mannose (Man), glucosamine (GcN), 2-deoxyglucose (2DG) and fructose (Fru), while strain LAC5 showed the activities only for Man and Fru. These activities were all constitutive. Growth of both strains was strongly inhibited by 2DG. 2DG-resistant mutants DG329 and DG504 were isolated, respectively, from strains LAC3 and LAC5. Mutant DG329 grown on Glc was defective in all the above-described activities observed with strain LAC3, whereas no defect in PTS activities was found in mutant DG504. Mutant DG329, however, showed some inducible activities for Man and Fru when grown on Man, Fru or Scr. These results strongly suggest that strain LAC3 has inducible PTS(s) specific for Man and/or Fru besides the well-known, broadly specific, constitutive Man-PTS, and also that strain LAC5 lacks the Man-PTS, but has other constitutive PTS(s) specific for Man and/or Fru. L. fermentum LAC12 had the Man-PTS as reported previously (Nagasaki et al., 1992), but had no inducible activities like those found in strain LAC3.