S. thermophilus has more than 50 regions of anomalous GC content, most of which are associated with genes of relevance to milk adaptation. A region of particular interest

is a fragment which is 95% identical to the metC gene from Lb. delbrueckii. The product of the metC gene allows methionine biosynthesis, a rare amino acid in milk. This high level Oligomycin A ic50 of identity suggests a recent lateral gene transfer event between two distantly related species occupying the same environmental niche [13]. These regions of laterally transferred genes are consistent with recently acquired chromosomal regions or genomic islands that have been described in the PLX-4720 purchase multi-niche bacterium Lb. plantarum [37], but not in the gut specific bacteria. These genomic islands are

thought to increase the ability of Lb. plantarum to adapt to multiple environmental niches [38]. Of the other multi-niche bacteria, they have evolved in different ways to be able to adapt to multiple niches. Lb. sakei was isolated from meat but can also survive the gut. To this end, it has acquired (most likely through lateral gene transfer) numerous additional metabolic and stress genes allowing it to adapt to a multitude of environmental niches [39]. In specific environmental niches, particularly dairy, plasmids are undoubtedly of significant importance. mTOR inhibitor Plasmids, which are omnipresent in LAB, often encode for genes with technologically important traits and are also seen as major contributors to the metabolic capabilities Histidine ammonia-lyase of a cell. For example, Lb. salivarius harbours three plasmids which consist of additional metabolic genes, increasing the overall metabolic capacity and perhaps allowing it to survive in

a variety of environmental niches [20]. Conclusion The dairy strain Lb. helveticus DPC4571 and the gut strain Lb. acidophilus NCFM share remarkable genetic relatedness despite coming from such differing niches. We performed an all-against-all BLAST search between Lb. helveticus DPC4571 and Lb. acidophilus NCFM, which identified 626 genes that differed between the two, potential niche identifier genes. Using a threshold of 1e-10 and greater than 30% identity for homologue detection we searched each of the 626 genes against an eleven genome group. From this analysis 9 genes emerged as being niche specific i.e., genes which were found solely in organisms associated with the gut or genes found solely in organisms associated with the dairy environment. We observed that these 9 genes were involved in characteristics desirable for gut or dairy survival, namely sugar metabolism, the proteolytic and R/M systems and bile-salt hydrolysis. Simultaneously to this unbiased bioinformatic test we examined in depth all genes involved in dairy and gut characteristic traits for niche-specific genes and interestingly we ended up with the same 9 gene “”barcode”".