Rhizosphere microorganisms typically coexist within complex multispecies biofilm communities. However, the interspecies interactions within these biofilm-associated microbial consortia remain largely unexplored. A synthetic bacterial SynCom Q was previously constructed in our laboratory for controlling watermelon Fusarium wilt. This study simplified SynCom Q into SynCom Y ( Agrobacterium deltaense LSQ16 and Bacillus velezensis WB) using a stepwise strain omission strategy and combined genome-scale modeling with multi-omics analyses to reveal mechanisms of synergistic biofilm formation. Co-cultivation of A. deltaense LSQ16 and B. velezensis WB significantly enhanced biofilm formation. Compared with monocultures, co-cultivation also markedly increased extracellular polysaccharide production and metabolic activity. SynCom Y effectively enhances resistance to the pathogen through the promotion of biofilm formation. Compared with monocultures, co-cultivation led to the upregulation of genes associated with extracellular polysaccharides (EPS) synthesis, biofilm formation, and quorum sensing pathways. Meanwhile, microbes within the mixed-species biofilm cooperatively regulated the production of the extracellular matrix to enhance biofilm development. Predictive results indicated metabolite exchange between the two strains involved amino acids, purines, phosphates, and other compounds. Moreover, exogenous supplementation of L-ornithine and guanine further enhanced the biofilm-forming capacity of B. velezensis WB. Our results indicate that a synergistic biofilm was formed through metabolic cooperation by Agrobacterium deltaense LSQ16 and Bacillus velezensis WB in co-cultures. • Strains Agrobacterium deltaense LSQ16 and Bacillus velezensis WB synergistically interacted through metabolic cooperation. • Mixed-species biofilms enhance biofilm structural stability and environmental adaptability. • Co-cultivation promotes the DEGs associated with quorum sensing and the c-di-GMP signaling pathway.
Zhang et al. (Fri,) studied this question.