New evidence for interspecific interactions between the specific spoilage organisms Pseudomonas fragi and Brochothrix thermosphacta

Researches on chilled meat spoilage increasingly emphasizes that spoilage outcomes emerge from interactions within diverse microbiota rather than from single dominant taxa. However, current understanding of key interacting species remains limited. This study profiled chilled chicken microbial communities and identified Brochothrix thermosphacta as a potential interactor with specific spoilage organism Pseudomonas fragi . Our findings demonstrate that gene-driven extracellular metabolites released by P . fragi modulate community composition and are associated with selective enrichment of Brochothrix . Through coculture assays with multiple B . thermosphacta , we observed strain-specific variations in aggregation, motility, biofilm formation, and extracellular protease activity. Notably, B. thermosphacta exhibiting strong biofilm formation capabilities dominated the coculture biofilm structure. This dominance underscores the key role of biofilm formation in microbial competition and persistence within meat ecosystems. Furthermore, our investigation identified the aprD gene as a crucial regulator, which regulates the dynamic interspecies interactions between P. fragi and B. thermosphacta . The aprD gene not only altered the extracellular metabolite profile of P. fragi , but also influenced meat microbial community assembly. These findings indicate that co-spoilage potential is strain-dependent and functionally specialized at the species level and provides new insights into how interspecific interaction influence microbial behavior and spoilage potential. • P. fragi alter the chilled chicken microbiome through extracellular metabolites. • Brochothrix engage in metabolic interactions with P. fragi. • AprD gene governs spoilage and interaction traits. • Coculture experiments revealed strain-dependent variations in biological properties.