Title: An azorhizobium-caulinodans ors571 locus involved in lipopolysaccharide production and nodule formation on sesbania-rostrata stems and roots
Authors: Goethals, Koen ×
Leyman, Barbara
Van Den Eede, Guy
Vanmontagu, Marc
Holsters, Marcelle #
Issue Date: Jan-1994
Publisher: American Society for Microbiology (ASM)
Series Title: Journal of Bacteriology vol:176 issue:1 pages:92-99
Abstract: Azorhizobium caulinodans ORS571 is able to nodulate roots and stems of the tropical legume Sesbania rostrata. An ORS571 Tn5 insertion mutant, strain ORS571-X15, had a rough colony morphology, was nonmotile, and showed clumping behavior on various media. When this pleiotropic mutant was inoculated on roots or stems of the host, no nodules developed (Nod(-)). Compared with the wild type, strain ORS571-X15 produced lipopolysaccharides (LPS) with an altered ladder pattern on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels, suggestive of a different O-antigen structure with a lower degree of polymerization. A cosmid clone, pRG20, that fully complemented all phenotypes of ORS571-X15 was isolated. With a 6-kb EcoRI subfragment of pRG20, clumping was relieved and nodulation was almost completely restored, but the strain was still nonmotile. LPS preparations from these complemented strains resembled the wild-type LPS, although minor quantitative and qualitative differences were evident. The sequence of the locus hit by the Tn5 in ORS571-X15 (the oac locus) revealed a striking homology,vith the rfb locus of Salmonella typhimurium, which is involved in O-antigen biosynthesis. The Tn5 insertion position was mapped to the oac3 gene, homologous to rfbA, encoding dTDP-D-glucose synthase. Biochemical assaying showed that ORS571-X15 is indeed defective in dTDP-D-glucose synthase activity, essential for the production of particular deoxyhexoses. Therefore, it was proposed that the O antigen of the mutant strain is devoid of such sugars.
ISSN: 0021-9193
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Non-KU Leuven Association publications
× corresponding author
# (joint) last author

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