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Summary:

Production of the expolysaccharide succinoglycan by Sinorhizobium meliloti strain 1021 is required for invasion and productive symbiosis in the hosts Medicago truncatula and Medicago sativa (alfalfa). S. meliloti succinoglycan biosynthesis mutants that do not produce any of the polysaccharide cannot induce infection thread formation. We have found that the molecular weight size distribution of succinoglycan is not critical for symbiotic function. Cleavage of succinoglycan by the glycanases ExoK and ExsH to produce the low molecular weight forms enhances the efficiency of invasion, but is not required. In free-living S. meliloti, each of these glycanases participates in resistance to different stresses and enhances survival. In order to function in infection thread formation, succinoglycan must be succinylated by the product of the S. meliloti exoH gene. Differences in both the symbiotic phenotypes and the free-living phenotypes of S. meliloti exoH mutants will be discussed.

Bio:

Kathryn M. Jones is an Associate Professor at Florida State University, in Florida, USA. Her lab focuses on S. meliloti factors that contribute to host plant invasion and survival within the nodule and on Sinorhizobium bacteriophages and their effects on population dynamics in soil.