Molecular cloning of the rfb region of Klebsiella pneumoniae serotype O1:K20: the rfb gene cluster is responsible for synthesis of the D-galactan I O polysaccharide.
Previous chemical analyses identified two structurally distinct O polysaccharides in the lipopolysaccharide of Klebsiella pneumoniae serotype O1:K20 (C. Whitfield, J. C. Richards, M. B. Perry, B. R. Clarke, and L. L. MacLean, J. Bacteriol. 173:1420-1431, 1991). The polysaccharides were designated D-galactan I and D-galactan II; both are homopolymers of galactose. To begin investigation of the synthesis and expression of these O polysaccharides, we have cloned a 7.3-kb region of the chromosome of K. pneumoniae O1:K20, containing the his-linked rfbkpO1 (O-antigen biosynthesis) gene cluster. In Escherichia coli K-12 and Salmonella typhimurium, rfbkpO1 directed the synthesis of D-galactan I but not D-galactan II. The cloned rfbkpO1 genes did not complement a mutation affecting D-galactan II synthesis in K. pneumoniae CWK37, suggesting that another (unlinked) locus is also required for D-galactan II expression. However, plasmids carrying rfbkpO1 did complement a mutation in K. pneumoniae CWK43 which eliminated expression of both D-galactan I and D-galactan II, indicating that at least one function is common to synthesis of both polymers. Synthesis of D-galactan I was dependent on chromosomal galE and rfe genes. Hybridization experiments indicated that the rfbkpO1 sequences from different serotype O1 Klebsiella isolates showed some restriction fragment length polymorphism.
Clarke
B R
BR
Department of Microbiology, University of Guelph, Ontario, Canada.
Whitfield
C
C
D003001:Cloning, Molecular; D005685:Galactans / Q000096:biosynthesis / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D007711:Klebsiella pneumoniae / Q000235:genetics* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000096:biosynthesis / Q000235:genetics*; D005810:Multigene Family / Q000235:genetics*; D019081:O Antigens; D010641:Phenotype; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000235:genetics*
D005685:Galactans; D008070:Lipopolysaccharides; D019081:O Antigens; D011135:Polysaccharides, Bacterial