Phylogenetic analysis supports horizontal gene transfer of l-amino acid oxidase gene in Streptococcus oligofermentans

► Phylogenetic analysis showed relationship of Streptococcus oligofermentans to other species of Streptococcus. ► l-amino acid oxidase (LAAO) of S. oligofermentans confers ability to compete in oral environment. ► l-amino acid oxidase (LAAO) of S. oligofermentans was obtained by horizontal transfer from other Streptococcus group.