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

Phylogenetic analysis of 10 amino acid sequences from 19 Streptococcus species showed that S. oligofermentans clustered within the mitis group. However, the l-amino acid oxidase (LAAO) of S. oligofermentans showed a different clustering pattern from the other proteins analyzed implicating horizontal gene transfer (HGT) in the origin of the S. oligofermentans LAAO gene. LAAO of S. oligofermentans is known to confer ability to compete with other oral cavity bacteria, most notably S. mutans; therefore, the HGT event may have been important in extending the ecological niche occupied by this species, consistent with those of other studies suggesting that HGT can play a key role in enabling bacterial species to occupy new ecological niches.