Comparative genetic study reveals glycanase mutations disrupt exopolysaccharide cleavage in Rhizobium leguminosarum, indicating their requirement for effective pea symbiosis.
Key Points
To identify the enzymatic mechanisms responsible for generating low-molecular-weight acidic exopolysaccharides in symbiotic Rhizobium leguminosarum bv. viciae VF39.
Engineered single (plyB), double (plyBC, pssWplyB), and triple (pssWplyBC) glycanase gene knockout mutants in Rhizobium leguminosarum bv. viciae VF39.
Assessed polysaccharide polymerization and oligosaccharide yield in culture media using viscometric, quantitative, and mass spectrometric analyses.
Evaluated the symbiotic performance of wild-type and mutant bacterial strains during nodule formation on garden pea (Pisum sativum).
Glycanase knockout mutants produced exopolysaccharides with higher degrees of octasaccharide unit polymerization and lower amounts of acidic exo-oligosaccharides in culture media than the wild-type strain.
Depolymerization efficiency of extracellular polysaccharide lyases PlyBC required the presence of functionally active periplasmic glycoside hydrolase PssW.
Symbiotic effectiveness with garden pea was markedly impaired in double mutant plyBC and triple mutant pssWplyBC strains.