Compositional assessment of bacterial communities in probiotic supplements by means of metagenomic techniques.

Health promoting or probiotic bacteria are commonly incorporated into a variety of functional foods and drug formulations, due to their purported ability to confer benefit to host health. Despite the extensive commercial exploitation of probiotic formulations there are still major knowledge gaps regarding the precise molecular mechanism of action and corresponding genetic/genomic properties of probiotic bacteria. In the current study, we describe a metagenomic approach which allows determination of the composition of probiotic supplements through next-generation sequencing analyses based on rRNA-associated sequences to assess bacterial composition of the product combined with a shotgun metagenomics approach directed to decode the genome sequences of the probiotic strains for each product assayed. The here developed approach has been tested for 10 probiotic supplements, revealing inconsistencies between the identified probiotic strains and the declared strains as indicated by the producers. Furthermore, the decoded bacterial genome sequence of Bifidobacterium animalis subsp. lactis BB-12 from a 1995 frozen dried stock revealed genetic evidence for genome evolution and stability of this microorganism when compared with the re-constructed genome of the identical strain from a probiotic supplement of 2017.