M DUBEY¹, J R VAN DER MEER<sup>1

1</sup>Department of Fundamental Microbiology, University of Lausanne, Quartier Unil-Sorge, Biophore building, 1015 Lausanne, Switzerland

Microbial ecosystem engineering approaches often rely on the introduction of one or more selected species into an existing microbial community. The success of introduced species to a large extent depends on the types of interactions that it is developing with other existing microbes, such as neutralism, commensalism, syntrophism or competition. Deciphering the rules governing microbial species' interactions is a strenuous task.

Our project is focused on better understanding the principles of success of establishing pure cultures in complex microbial ecosystems such as contained within soil. Here we develop a high-throughput co-cultivation approach that might enable us to study the species' "interactome", the identification of favourable and non-favourable species combinations that decide on the survival of the inoculant in the community. We use agarose micro-beads as growth chambers to randomly combine soil community members with or without pure culture inoculants. Growth of co-cultured species members is followed by microscopy and enables a global overview of potentially positive effects of the inoculant on growth of the members in the soil on specific carbon substrates. In addition, the “interactome” study allows detecting possible species pairs, negative or positive, that can be recovered and identified in detail. The resulting knowledge not only provides ample data in designing functional synthetic communities but also construct new avenues for “synthetic ecology”.