The rkpGH1 and -J genes are involved in capsular polysaccharide production by Rhizobium meliloti

Ernö Kiss, Bradley L. Reuhs, John S. Kim, Attila Kereszt, György Petrovics, Péter Putnoky, Ilona Dusha, Russell W. Carlson, Ádám Kondorosi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

The first complementation unit of the fix-23 region of Rhizobium meliloti, which comprises six genes (rkpAB-CDEF) exhibiting similarity to fatty acid synthase genes, is required for the production of a novel type of capsular polysaccharide that is involved in root nodule development and structurally analogous to group II K antigens found in Escherichia coli (G. Petrovics, P. Putnoky, R. Reuhs, J. Kim, T. A. Thorp, K. D. Noel, R. W. Carlson, and A. Kondorosi, Mol. Microbiol. 8:1083-11194, 1993; B. L. Reuhs, R. W. Carlson, and J. S. Kim, J. Bacteriol. 175:3570-3580, 1993). Here we present the nucleotide sequence for the other three complementation units of the fix-23 locus, revealing the presence of four additional open reading frames assigned to genes rkpGHI and -J. The putative RkpG protein shares similarity with acyltransferases, RkpH is homologous to short-chain alcohol dehydrogenases, and RkpJ shows significant sequence identity with bacterial polysaccharide transport proteins, such as KpsS of E. coli. No significant homology was found for RkpI. Biochemical and immunological analysis of Tn5 derivatives for each gene demonstrated partial or complete loss of capsular polysaccharides from the cell surface; on this basis, we suggest that all genes in the fix-23 region are required for K-antigen synthesis or transport.

Original languageEnglish
Pages (from-to)2132-2140
Number of pages9
JournalJournal of Bacteriology
Volume179
Issue number7
DOIs
StatePublished - 1997
Externally publishedYes

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