Acquisition of pcnB [poly(A) polymerase I] genes via horizontal transfer from the β, γ-Proteobacteria

Poly(A) polymerases (PAPs) and tRNA nucleotidyltransferases belong to a superfamily of nucleotidyltransferases and modify RNA 3′-ends. The product of the pcnB gene, PAP I, has been characterized in a few β-, γ- and δ- Proteobacteria . Using the PAP I signature sequence, putative PAPs were identified in bacterial species from the α- and ε- Proteobacteria and from four other bacterial phyla ( Firmicutes , Actinobacteria , Bacteroidetes and Aquificae ). Phylogenetic analysis, alien index and G+C content calculations strongly suggest that the PAPs in the species identified in this study arose by horizontal gene transfer from the β- and γ- Proteobacteria .