Most biofilms within the food industry are formed by multiple bacterial specieswhich co-exist on surfaces as a result of interspecies interactions. These ecologicalinteractions often make these communities tolerant against antimicrobials.Our previous work led to the identification of a large number (327) of highlydiverse bacterial species on food contact surfaces of the dairy, meat, and eggindustries after routine cleaning and disinfection (C&D) regimes. In the currentstudy, biofilm-forming ability of 92 bacterial strains belonging to 26 genera and42 species was assessed and synergistic interactions in biofilm formation wereinvestigated by coculturing species in all possible four-species combinations.Out of the total 455 four-species biofilm combinations, greater biofilm massproduction, compared to the sum of biofilm masses of individual species inmonoculture, was observed in 34 combinations. Around half of the combinationsshowed synergy in biofilm mass > 1.5-fold and most of the combinations belongedto dairy strains. The highest synergy (3.13-fold) was shown by a combination ofdairy strains comprising Stenotrophomonas rhizophila, Bacillus licheniformis,Microbacterium lacticum, and Calidifontibacter indicus. The observed synergy inmixed biofilms turned out to be strain-specific rather than species-dependent.All biofilm combinations showing remarkable synergy appeared to have certaincommon species in all combinations which shows there are keystone industryspecificbacterial species which stimulate synergy or antagonism and this mayhave implication for biofilm control in the concerned food industries.