RNA sequencing reveals the involvement of quorum sensing in dairy spoilage caused by psychrotrophic bacteria

Abstract

Dairy spoilage caused by psychrotrophic bacteria has been reported to be regulated by acyl-homoserine-lactones (AHLs)-based quorum sensing (QS) system. However, the precise role of AHLs produced by psychrotrophic bacteria in dairy spoilage remains unclear. The aim of this study was to evaluate the effects of AHLs on dairy spoilage caused by Pseudomonas azotoformans and Serrita liquefaciens at the transcriptional level. The particle size and volatile compounds of milk were selected as spoilage indicators for investigating the involvement of AHLs in dairy spoilage. Furthermore, the in situ gene expressions of psychrotrophic bacteria in AHLs-treated milk during cold storage were explored by RNA sequencing for the first time. The results revealed that the milk particle size and content of acids in milk were increased by exogenous AHLs, which confirm the enhancing effect of AHLs on the quality deterioration of milk. Transcriptome analysis revealed that a number of core genes of strains were significantly differentially expressed when treated with exogenous AHLs, and QS coordinate the metabolic processes within tested strains. Most of genes involving in the bacterial growth and metabolism, enzymes production, and stress response were up-regulated by exogenous AHLs. The results elucidate the potential involvement of AHLs in dairy spoilage caused by psychrotrophic bacteria. This would give clue for novel strategy of controlling microbial spoilage in dairy products.