Acquisition of pcnB [poly(A) polymerase I] genes via horizontal transfer from the beta, gamma-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 beta-, gamma- and delta-Proteobacteria. Using the PAP I signature sequence, putative PAPs were identified in bacterial species from the alpha- and epsilon-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 beta- and gamma-Proteobacteria.