Identification and cloning of a cyclic beta-(1-->3), beta-(1-->6)-D-glucan synthesis locus from Bradyrhizobium japonicum

Abstract

A cosmid clone complementing a cyclic beta-(1-->2)-glucan biosynthesis (ndvB) mutant of Rhizobium meliloti was isolated from a Bradyrhizobium japonicum gene library. This clone specified synthesis of beta-(1-->3), beta-(1-->6)-linked glucans in R. meliloti. The complemented strain was osmotically tolerant and symbiotically competent on alfalfa. Thus, beta-(1-->3), beta-(1-->6)-glucans can substitute functionally for beta-(1-->2)-glucans in R. meliloti.