INDUCER EXPULSION AND THE OCCURRENCE OF AN HPR(SER-P)-ACTIVATED SUGAR-PHOSPHATE PHOSPHATASE IN ENTEROCOCCUS-FAECALIS AND STREPTOCOCCUS-PYOGENES

Inducer expulsion, a phenomenon in which rapidly metabolizable sugars cause cytoplasmic dephosphorylation and efflux of pre-accumulated suga r-phosphates (sugar-P), has been documented for Streptococcus pyogenes , Streptococcus bovis, and Lactococcus lactis, but not for other Gram- positive bacteria. Using intact cells sad membrane vesicles, we show t hat Enterococcus faecalis exhibits both inducer exclusion and inducer expulsion, and that the latter phenomenon is dependent on the metaboli te-activated ATP-dependent HPr(Ser) kinase that phosphorylates Ser-46 in HPr of the phosphotransferase system. A small, heat-stable, membran e-associated, HPr(Ser-P)-activated sugar-P phosphatase (Pase II), prev iously identified only in Lc. lactis, is shown to be present in extrac ts of Enterococcus faecalis and Streptococcus pyogenes but not in thos e of Staphylococcus aureus, Streptococcus mutans, Streptococcus saliva rius, or Bacillis subtilis, organisms that do not exhibit the inducer expulsion phenomenon. Further, Lactobacillus brevis, an organism that exhibits inducer expulsion by a different mechanism, also apparently l acks Pase II. The results reveal that Pase II is present in those orga nisms that exhibit the coupled sugar-P hydrolysis/expulsion mechanism but not those that lack this mechanism. They provide correlative evide nce that Pase II initiates inducer expulsion in species of enterococci , streptococci and lactococci.