Numerous bacterial species utilize quorum sensing molecules acyl-homoserine-lactones (AHLs) to communicate, however, crosstalk often complicates the dynamics and behaviors of mixed populations. In this study, we developed a mutant of wild type SA03 (WT SA03), and aimed to investigate the role of LuxR (AHLs receptor) involved in the spoilage of refrigerated shrimp () by inoculating WT SA03 and mutant of SA03 ( SA03), respectively. The results indicated the maximum growth rate of total viable bacteria in shrimp inoculated with SA03 was 73.34% lower than that of WT SA03. The lag time of total bacteria in shrimp treated with SA03 were 87.6 h, significantly longer than that of WT SA03. Meanwhile, the total volatile basic nitrogen concentrations of shrimp treated with WT SA03 were significantly higher than that of SA03 after 2 days of storage, which were in agreement with the decrease of the content of AHLs of the shrimp. The results indicated might utilize AHLs produced by other bacteria and accelerate the shrimp spoilage process through LuxR receptor system.

Shewanella baltica is the predominant bacteria in spoiled shrimp (Litopenaeus vannamei), however, the spoilage ability and the mechanism of S. baltica is still unknown. S. baltica can't produce the signal molecule of acyl-homoserine-lactones (AHLs), so the aim of this study was to investigate how wild type S. baltica SA03 (WT SA03) eavesdrop exogenous AHLs to enhance its spoilage ability through LuxR receptor. The results indicated that Aeromonas spp. (Aer), Acinetobacter spp. (Aci) and Serratia spp. (Ser) isolated from refrigerated shrimp can produce different AHLs. WT SA03 can eavesdrop the AHLs of Aer (C4-HSL), Aci (O-C6-HSL) and Ser (C6-HSL, O-C6-HSL) to enhance its growth, especially Ser. Exogenous C4-HSL and C6-HSL enhanced biofilm formation of WT SA03, and C6-HSL and O-C6-HSL enhanced thioredoxin reductase trxB mRNA expression. However, the luxR mutant of WT SA03 (DluxR SA03) lost or weakened the role of using environmental AHLs. In vivo experiments, the lag time of WT SA03 was shortened by 6.4 h, 6.2 h and 14.4 h by co-inoculated with Aer, Aci and Ser, respectively. The total volatile basic nitrogen (TVB-N) were significantly enhanced in the samples co-inoculated with WT SA03 and Aer (or Aci, Ser) than those of DluxR SA03 and Aer (or Aci, Ser) (p \ 0.05). The results showed that S. baltica SA03 can utilize AHLs produced by other bacteria to enhance its growth and spoilage ability through LuxR receptor system. Quorum sensing based on AHLs of bacteria might as the potential targets for food spoilage control. KeywordsShewanella baltica Á Quorum sensing Á Eavesdropping Á Acyl-homoserine-lactones Á Spoilage ability Abbreviations WT SA03 Wild type Shewanella baltica SA03 DluxR SA03 The luxR mutant of Shewanella baltica SA03 Aer Aeromonas spp. Aci Acinetobacter spp. Ser Serratia spp. C4-HSL N-butanoyl-L-homoserine lactone C6-HSL N-hexanoyl-L-homoserine lactone C8-HSL N-3-hydroxyoctanoyl-L-homoserine lactone O-C6-HSL N-(3-oxohexanoyl)-L-homoserine lactone O-C8-HSL N-(3-oxo hydroxyoctanoyl)-L-homoserine lactone