Characterization of a Rhizobium meliloti ndvB Mutant and a Symbiotic Revertant that Regains Wild-Type Properties. María J. Soto. Departamento de Microbiología, Estación Experimental del Zaidín, C.S.I.C., Granada, Spain. Viviana Lepek, Isabel M. López-Lara, José Olivares, and Nicolás Toro. Departamento de Microbiología, Estación Experimental del Zaidín, C.S.I.C., Granada, Spain.. MPMI 5:288-293. Accepted 26 February 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1992.

Rhizobium meliloti mutant strain GRT21s, which is generated by heat treatment, was previously reported not to form cyclic Beta-(1-2)-glucan in vivo or in vitro. The mutant lacks a 235-kilo-dalton (kDa) protein that acts as an intermediate in Beta-(1-2)-glucan synthesis. In this work, we genetically characterized strain GRT21s as a ndvB mutant and selected a symbiotic revertant (GRT21sR) that restored Beta-(1-2)-glucan synthesis as well as other vegetative properties altered in strain GRT21s. Furthermore, by two-dimensional gel electrophoresis, we identified a group of membrane proteins linked to Beta-(1-2)-glucan synthesis. Our data indicate that NdvB protein and/or cyclic glucans influence proper functioning of such important systems as motility, adaptation to low osmolarity, and nodule formation, as well as alterations in membrane protein composition.