Resolving phylogenetic history of Enterococcus mundtii using all enterococci core protein sequences

LUIS ESTEBAN, VÍCTOR S. BLANCATO, INGRID QUINTANA, CHRISTIAN MAGNI, MARTÍN ESPARIZ.

Rosario

Congreso; 4to. Congreso Argentino de Bioinformática y Biología Computacional (4CAB2C) y 4ta. Conferencia Internacional de la Sociedad Iberoamericana de Bioinformática (SolBio); 2013

Sociedad Iberoamericana de Bioinformática (SolBio)

Enterococcus genera include commensal, environmental and human pathogen bacteria. For that reason, accurate identification is indispensable for both environmental and clinical studies. While phylogenetic trees based on comparative analysis of the 16S rDNA sequences is a standard identification and classification procedure, it was previously stated that some environmental strains of enterococci were incorrectly identified to the species level using this method [1]. E. mundtii CRL1656 is a pigmented bacterium that was isolated from stripping milk of an Argentinean cow and its genome was recently sequenced [2]. The aim of this study was to properly infer the phylogenic history of the strain. We observed that E. mundtii is more related to E. faecium species (Figure 1A). Noteworthy, other pigmented species, such as E. casseliflavus are phylogenetically more distant. To quantify the relationships among these enterococcal species, we generated average nucleotide identity (ANI) plots (Figure 1B), which have been used to query and refine prokaryotic species definitions. As expected, ANI values were lower than the 94% accepted as a threshold for species designation. E. faecium strains showed the highest ANI values (around 76 %), with a shared gene content between 87 and 89%. With respect to other enterococcal species, ANI varies within a narrow range (approximately 72%) but shared gene content is more disperse (75 to 82%). Our study reveals that E. mundtii shares a higher number of gene functions with E. faecium. With respect to other enterococcal species analyzed, all of them share a similar ANI with E. mundtii, however E. faecalis strains showed the lower percentage of shared genes, which might indicate that the niche occupied by E. mundtii might be closer to that were environmental strains are present.