Abstract
Sturgeon is an important fresh water-culture fish in China. A problem with sturgeon is its high susceptibility to spoilage. Food spoilage is reported to be regulated by quorum sensing (QS). To identify the QS signals acetylated homoserine lactones (AHLs) in sturgeon and test whether QS plays a role in the spoilage of sturgeon, we investigated the specific spoilage organisms (SSOs) in vacuum packaged sturgeon stored at 4°C and the production of AHLs by sturgeon SSOs. 16S rDNA sequencing and spoilage capabilities analysis revealed that Aeromonas veronii LP-11, Citrobacter freundii LPJ-2, and Raoultella ornithinolytica LPC-3 were the SSOs in sturgeon. Among the three SSOs, only A. veronii LP-11 induced the QS biosensors Agrobacterium tumefaciens KYC55 and Chromobacterium violaceum CV026, suggesting that it produced AHLs. Analysis by thin layer chromatography, high-performance liquid chromatography-triple quadrupole tandem mass spectrometry, and high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC/qTOF-MS) identified that the AHLs produced by A. veronii were C6-SHL, C8-HSL, 3-oxo-C8-HSL, and 3-OH-C8-HSL. Our study revealed that QS system was probably involved in the regulation of sturgeon spoilage and for the first time reported the production of C8-HSL and 3-OH-C8-HSL by genus Aeromonas. As only HPLC/qTOF-MS effectively and accurately identified all the four AHLs produced by A. veronii LP-11, this study also showed that HPLC/qTOF-MS was the most efficient method for rapid analysis of AHLs in complex microbial sample. The study provides new insight into the microbiology of sturgeon spoilage which may be helpful for better sturgeon preservation.
Highlights
Sturgeon is economically one of the most important fresh water-cultured fish in China, of which the production in China takes up to 80% of the total production in the world
It can be concluded that spots a, b, and c were 3-oxo-C8-HSL, C8-HSL and C6-HSL, respectively, but spot d was an unidentified Acetylated homoserine lactones (AHLs); these results demonstrated that at least four different AHLs were synthesized by A. veronii LP-11
A. veronii LP-11, Citrobater freundii LPJ-2, and Raoultella ornithinolytica LPC-3 which belong to Aeromonas and Enterobacteriaceae were identified to be the specific spoilage organisms (SSOs) of vacuum packaged sturgeon stored at 4◦C
Summary
Sturgeon is economically one of the most important fresh water-cultured fish in China, of which the production in China takes up to 80% of the total production in the world. One problem with sturgeon is its high susceptibility to spoilage due to the high water content and nutrients For this reason, refrigeration and vacuum packing are commonly used for the storage and transportation of sturgeon products. QS signals have been detected in a variety of different spoiled commercial aquatic products, such as cold-smoked fish fillets, packed or refrigerated fish, and shrimp (Christensen et al, 2003; Flodgaard et al, 2005; Bai and Rai, 2011; Zhu et al, 2015, 2016). AHLs are detected in Shewanella putrefaciens, the SSO of refrigerated shrimp (Zhu et al, 2015) Taken together, these reports demonstrate that AHL-based QS system in Gramnegative bacteria is involved in the spoilage of some aquatic products. The mechanism of QS in sturgeon spoilage and their precise role in spoilage is still not clear
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