Interactions between Salmonella Enteritidis and food processing facility isolate Bacillus paramycoides B5 in dual-species biofilms

Abstract

Foodborne pathogens tend to live in mixed-species biofilms with resident flora in the food industry, likely posing a higher risk of pathogen contamination due to the strong biofilm formation and disinfectant resistance. The behavior of Salmonella Enteritidis (SE) in the presence of the food-processing environmental bacterium Bacillus paramycoides B5 (Bp5) during dual-species biofilm formation were investigated by Illumina RNA-seq transcriptome analysis combined with phenotype validation. The results showed that SE initial adhesion was significantly enhanced with large microcolony formation when cocultured with Bp5. The cocultures formed more extracellular polymeric substances compared to SE mono-species. Transcriptome analysis showed that a total of 433 differentially expressed genes (DEGs) of SE were present in dual-species biofilms. Functional annotation revealed that the genes involved in bacterial chemotaxis, flagellar assembly, and two-component system pathways were significantly upregulated. Genes involved in amino acid biosynthesis and metabolism, oxidative phosphorylation, and the citrate cycle were downregulated. Selected genes belonging to SE biofilm formation and environmental resistance were significantly upregulated with RT-qPCR validation. Flagellar-mediated motility was enhanced. This study explored the underlying mechanisms of enhanced biofilm formation and environmental resistance of SE in dual-species biofilms, which may help reveal or resolve SE persistence in food processing environments.