Structural analysis of lipopolysaccharides from Sinorhizobium sp. NGR234 induced by apigenin
Abstract
The symbiotic relationship between rhizobia and legume requires complex signal exchanges and recognition mechanisms. Bacterial polysaccharides, such as exopolysaccharide (EPS), capsular polysaccharide (KPS) and lipopolysaccharide (LPS), also function as signal molecules and play critical roles in different stages of the symbiotic process. When Sinorhizobium sp. NGR234, a fast growing rhizobium with a broad host range, was grown in a culture containing a flavonoid of plant origin, it produced a novel LPS with a L-rhamnan O-antigen. The deletion of genes related to L-rhamnose synthesis ( rmlB, rmlD, rmlA, and wbgA) blocked the production of L-rhamnan-LPS, and the mutant was defective in nodule infection on its host plant. In addition, the mutant produced a novel rough-type LPS with very high mobility (vhm-LPS) on electrophoresis gels. In the present research, the rhamnan-LPS, vhm-LPS, and rough-LPSs were isolated by improved chromatographic and electrophoretic techniques. Structural analyses of the LPSs by HPAEC-PAD, GC-MS and MALDI-MS showed that vhm-LPS is a rhamnan O-antigen receptor, but the deletion of those genes also modulates the structure of core region. This result suggests the importance of rhamnan-LPS in symbiosis and helps to understand the exact role of a bacterial surface antigenic variation under different environments.
Degree
Ph.D.
Advisors
Reuhs, Purdue University.
Subject Area
Agronomy
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