Degree Name

Master of Science (MS)

Semester of Degree Completion

1982

Thesis Director

Russell Carlson

Abstract

The Rhizobium extracellular polysaccharides (EPS) and lipopolysaccharides (LPS) are implicated in the symbiotic process. The interaction between host root protein fractions and symbiont EPS-polyacrylamide affinity support has been investigated. Ten percent root protein fractions had been observed to bind to the affinity support. The compositions of the polysaccharides from the parent R. leguminosarum and its Exo-1 mutant have also been compared. The Exo-1 mutant produces diminished amount of EPS and does not nodulate the host pea roots. Five kinds of polysaccharides from the parent were obtained: EPS, capsule polysaccharides (CPS I) washed from the bacteria with saline solution, LPS, small polysaccharides (SmPS) and the polysaccharides remaining in the supernatant from the ultracentrifugation of the impure viscous LPS solution (CPS 2a). The compositions of the EPS, CPS I, and CPS 2a are identical. The Exo-1 mutant also produces EPS (1-7%) and a small amount of CPS I. This EPS and CPS consists solely of LPS and SmPS. None of the parental type acidic EPS and CPS are produced by the Exo-1 mutant. In addition, the Exo-1 mutant produces LPS polysaccharide fragments. The LPS from the mutant and parent are identical to each other in their compositions, both the core and the O-antigen regions. The O-antigen sugar linkages were also compared by using methylation analysis and the linkages of the O-antigen from the parent and the mutant are also identical. The meaning of these results is discussed with regard to the role of Rhizobium surface polysaccharides in symbiosis.

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