mucS, a Gene Involved in Activation of Galactoglucan (EPS II) Synthesis Gene Expression in Rhizobium meliloti. Sabina G. Astete. Department of Microbiology, University of Washington, Seattle, WA 98195 U.S.A. John A. Leigh Department of Microbiology, University of Washington, Seattle, WA 98195 U.S.A. MPMI 9:395-400. Accepted 18 March 1996. Copyright 1996 The American Phytopathological Society.

In addition to the exopolysaccharide succinoglycan, Rhizobium meliloti can produce a galactoglucan exopolysaccharide, EPS II. The production of EPS II occurs in certain mutant strains, in strains containing extra copies of EPS II synthesis genes, or in (he wild-type strain under phosphate-limiting conditions. We have identified a gene, mucS, that is in a locus required for EPS II induction by extra gene copies and by phosphate limitation, and that activates the expression of at least one other EPS II synthesis gene. mucS lies within a cluster of EPS II synthesis genes and contains an open reading frame of 190 amino acids. MucS does not show any significant similarity to known genes and may represent a new type of regulatory protein