Underestimated breadth and flexibility of bacterial interactions on polysaccharide hydrolysis of Saccharophagus degradans in binary co-culture.

Mechanisms underlying microbial interactions remain rarely documented in biomass processing, hindering development of biotechnology platforms relying on co-culture systems. In the present study, we investigated how bacterial interactions affect polysaccharide hydrolysis in binary co-cultures consisting of six highly clonal Saccharophagus degradans strains with distinct hydrolysis profiles and 63 taxonomically diverse bacteria (inducers). When evaluating pairwise interactions between the six S. degradans strains and 11 inducers (selected from the initial 63), we observed inhibitory effects on polysaccharide hydrolysis activity in 20.9% of the co-culture experiments, and promotive effects in 25.5% of the experiments. Notably, no consistent regulatory pattern was identified across any S. degradans strain, inducer, or polysaccharide tested. These results demonstrated the breadth, complexity, and flexibility of inter-species bacterial interactions regulating the polysaccharide hydrolysis activity of S. degradans within co-culture systems, underscoring the key challenges associated with elucidating such mechanisms in the context of polysaccharide bioconversion.