Background: Lactic acid bacteria (LAB constitute a significant group of microorganisms found in foods, but also contribute to human health. The Streptococcus bovis/ Streptococcus equinus complex within LAB includes members that have been implicated in human diseases, like endocarditis and colon cancer. Objectives: In this study we compared the three available genome sequences of Streptococcus macedonicus strains isolated from dairy products. Only one strain has its genome complete sequenced and previous analysis showed diminished pathogenic potential and adaptation to the milk environment. Here we present the in silico analysis of these strains, in order to better understand the S. macedonicus species. Methods: Chromosomal maps were constructed using DNA Plotter and whole genome sequence alignments were performed by progressiveMAUVE and Webact in order to visualize conserved genomic regions or chromosomal rearrangements. Genomic islands were identified and visualized by IslandViewer, potential bacteriocins were predicted by BAGEL3 and CRISPRs were analyzed by the tools available in the CRISPRcompar web-service. Conclusions: The analysis revealed that the strains have lost genes involved in the catabolism of complex plant carbohydrates, in the adhesion to the host’s cells and in haemolysis. On the other hand, an extra lactose operon and a proteolytic system characteristic of LAB were identified. Even though our whole genome analysis of S. macedonicus shows adaptation traits to the nutrient-rich dairy environment, analysis of additional S. macedonicus genomes, including non-dairy isolates, may be necessary to clarify its pathogenic potential.
