Molecular phylogeny and a taxonomic proposal for the genus Streptococcus.

Alternative phylogenies for the genus Streptococcus have been proposed due to uncertainty about the among-species group relationships. Here, we performed a phylogenetic analysis of the genus Streptococcus, considering all the species groups and also the genomic data accumulated by other studies. Seventy-five species were subjected to a Bayesian phylogenetic analysis using sequences from eight genes (16S rRNA, rpoB, sodA, tuf, rnpB, gyrB, dnaJ, and recN). On the basis of our results, we propose a new Phylogeny for the genus, with special emphasis on the inter-species group level. This new phylogeny differs from those suggested previously. From topological and evolutionary distance criteria, we propose that gordonii, pluranimalium, and sobrinus should be considered as new species groups, in addition to the currently recognized groups of mutans, bovis, pyogenic, suis, mitis, and salivarius.

Streptococcus massiliensis in the human mouth: a phylogenetic approach for the inference of bacterial habitats.

Streptococcus is a diverse bacterial lineage. Species of this genus occupy a myriad of environments inside humans and other animals. Despite the elucidation of several of these habitats, many remain to be identified. Here, we explore a methodological approach to reveal unknown bacterial environments. Specifically, we inferred the phylogeny of the Mitis group by analyzing the sequences of eight genes. In addition, information regarding habitat use of species belonging to this group was obtained from the scientific literature. The oral cavity emerged as a potential, previously unknown, environment of Streptococcus massiliensis. This phylogeny-based prediction was confirmed by species-specific polymerase chain reaction (PCR) amplification. We propose employing a similar approach, i.e., use of bibliographic data and molecular phylogenetics as predictive methods, and species-specific PCR as confirmation, in order to reveal other unknown habitats in further bacterial taxa.