Cloning and characterization of cobA, one of vitamin B12 biosynthesis pathway genes from Selenomonas ruminantium

Abstract

Bacterial biosynthesis of vitamin B12 can occur via either aerobic or anaerobic route. While the aerobic pathway has been fully elucidated and understood, less is known about the anaerobic pathway. Selenomonas ruminantium is thought to be the main producer of this vitamin in rumen environment and must use the anaerobic pathway. In our work we found one of the genes of vitamin B12 biosynthetic pathway of S. ruminantium, encoding for the cobalamin adenosyltransferase, enzyme taking part at the last steps of the synthesis process. Deduced amino acid sequence showed the highest similarity to cobalamin adenosyltransferases of other ruminal anaerobic bacteria and that of species Selenomonas. Phylogenetic comparisons of CobA protein sequences of several anaerobic bacteria of Clostridiale order indicate possible horizontal transfer of this gene.