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Title: A MOTILITY REVERTANT OF THE NDVB MUTANT OF BRADYRHIZOBIUM JAPONICUM

Author
item CHEN, RONGI - UNIV. OF CALGERY
item BHAGWAT, ARVIND - 1275-49-00
item KEISTER, DONALD - 1275-21000-149

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2003
Publication Date: 2/24/2003
Citation: Chen, R., Bhagwat, A.A., Keister, D.L. 2003. A motility revertant of the ndvb mutant of bradyrhizobium japonicum. Current Microbiology Vol. 47 (2003), pp. 431-433

Interpretive Summary: Bradyrhizobium japonicum are beneficial bacteria that form symbiotic associations with soybeans. This symbiosis supplies the plant with a source of nitrogen which can be used for protein synthesis. Improvement of the symbiotic association is important for decreasing the fertilizer nitrogen requirement of soybeans and for sustainable agriculture. Cyclic beta-glucans are small molecules composed solely of glucose, produced by the bacteria. Previously we described three genes, ndvB, C, and D required for the synthesis of beta-glucans. Mutation in ndvB results in bacteria that are non-motile, in addition to the defect in beta-glucan synthesis and symbiosis. This publication describes that restoration of motility in ndvB mutants is not sufficient to gain symbiotic effectiveness. The results support the hypothesis that beta-glucans have an important and specific role in symbiosis. This work is a step in the elucidation of how the bacteria suppress a plant defense response during the development of a nitrogen-fixing symbiosis and this is important in our efforts to improve the symbiotic association. This work will be used by scientists working to improve agricultural productivity.

Technical Abstract: A motility revertant of a Bradyrhizobium japonicum ndvB mutant was isolated and characterized. The ndvB mutants of B. japonicum have been reported to be osmotically sensitive, defective in motility, periplasmic cyclic B-(1¿3),(1¿6)-D-glucan synthesis and in symbiosis with soybean. The motility revertant was restored for osmotic tolerance but not for cyclic ß-glucan production or effective symbiosis. These results support our hypothesis that cyclic ß-glucans have an important role in symbiosis, the suppression of a plant defense response, in addition to their role in periplasmic osmoprotection.