This study investigated the dynamic social interactions within a four-species biofilm model (*Stenotrophomonas rhizophila*, *Bacillus licheniformis*, *Microbacterium lacticum*, and *Calidifontibacter indicus*) isolated from a dairy pasteuriser. The community exhibited significant synergy in biofilm mass production. The research confirmed that this synergy arises from dynamic interactions including commensalism, exploitation, and amensalism, with *M. lacticum* identified as a keystone species due to its growth-promoting effect on other species. Pairwise and higher-order interactions were analyzed, revealing the complex interplay of factors contributing to biofilm stability and functionality. These findings provide valuable insights into biofilm ecology and offer a potential interaction-mediated approach for cultivating and engineering synthetic bacterial communities.

Faizan Ahmed Sadiq, Koen De Reu, Hans Steenackers, Ann Van de Walle, Mette Burmølle, Marc Heyndrickx