Evidence for horizontal transfer from streptococcus to escherichia coli of the kfid gene encoding the K5-specific UDP-glucose dehydrogenase

Publisher Website
Google Scholar
Abstract
Capsular polysaccharides are important virulence factors both in Gram-positive and Gramnegative bacteria. A similar cluster organization of the genes involved in the synthesis of bacterial exopolysaccharides has been postulated in both cases, suggesting that these clusters evolved by module assembly. Horizontal gene transfer has been postulated to explain the polymorphism found in these cellular polymers. The caplK and cap3A genes coding for the pneumococcal type 1 and type 3 UDP-glucose dehydrogenases, respectively, have been compared with other UDP-sugar dehydrogenases. We have observed that the evolutionary distance between CaplK and Cap3A is approximately equal to that found between CaplK (or Cap3A) and other UDP-GlcDH of families evolutionary distant like KfiD, the dehydrogenase from Escherichia coli K5. On the basis of comparisons of G + C content, patterns of synonymous and nonsynonymous substitutions, dinucleotide frequencies, and codon usage bias, we conclude that the kfiD gene has been introduced into E. coli from an exogenous source, probably from a streptococcal species.