SIF 3rd Cohort Fellows - Marko Verce, University of Ljubljana

Overconsumption of sugary drinks leads to diabetes, cardiovascular diseases, and other negative health impacts. Fermented drinks, such as water kefir, are health-promoting alternatives that contain living yeasts, lactic acid bacteria, and sometimes bifidobacteria. Water kefir production relies on pre-existing water kefir grains. These dextran granules host dextran-producing, fermentative microorganisms, and their microbial composition varies between sources. For instance, bifidobacteria are not present in all water kefirs. Bifidobacterium is a bacterial genus that contains many species with probiotic properties and is generally thought to contribute to human health, yet little is known about its role in water kefir and the interactions with other microorganisms there. To ensure stability in the microbial composition of large- or small-scale water kefir productions, to modulate water kefir microbial composition, or even to engineer water kefir grains de novo, an indepth understanding of the water kefir ecosystem and its microbial interactions is needed and knowledge gaps need to be filled.

Therefore, we set three objectives:

1. to comprehensively analyse the microbial composition and gene expression in a Bifidobacteriumcontaining water kefir ecosystem through (meta)genomics and (meta)transcriptomics, revealing the genes necessary for microorganisms to participate in the water kefir ecosystem,
2. to categorise social interactions of the bifidobacterial member(s) with other ecosystem members in terms of transcription and growth,
3. to determine the ability of different Bifidobacterium strains to be incorporated into the water kefir ecosystem as stable members.