title: Quorum sensing signals affect spoilage of refrigerated large yellow croaker (Pseudosciaena crocea) by Shewanella baltica.
abstract: In this work we investigated the specific spoilage organism (SSO) of large yellow croaker (Pseudosciaena crocea) stored at 4°C and role of quorum sensing (QS) system of SSO isolated from the spoiled fish. According to microbial count and 16S rRNA gene of the isolated pure strains, Shewanella, mainly Shewanella baltica and Shewanella putrefaciens, was predominant genera at the end of shelf-life of P. crocea. Among Shewanella isolates, S.baltica02 was demonstrated as SSO in spoilage potential characteristics by inoculation into sterile fish juice using sensory and chemical analyses. Autoinducer 2 and two cyclic dipeptides (DKPs) including cyclo-(l-Pro-l-Leu) and cyclo-(l-Pro-l-Phe), no any AHLs, were detected in cell-free S. baltica culture. Interestingly, S.baltica02 had the highest QS activity among three spoilers of S. baltica. The production of biofilm, trimethylamines (TMA) and putrescine in these spoilers significantly increased in the presence of cyclo-(l-Pro-l-Leu), rather than cyclo-(l-Pro-l-Phe) and 4,5-dihydroxy-2,3-pentanedione (the AI-2 precursor, DPD). In accordance with the effect of signal molecules on the spoilage phenotype, exposure to exogenous cyclo-(l-Pro-l-Leu) was also showed to up-regulate the transcription levels of luxR, torA and ODC, and no effect of luxS indicated that S. baltica could sense cyclo-(l-Pro-l-Leu). In the fish homogenate, exogenous cyclo-(l-Pro-l-Leu) shortened lag phase durations and enhanced growth rates of the dominant bacteria, H2S producing bacteria, under refrigerated storage, while exogenous DPD retarded growth of competing bacteria, such as Enterobacteriaceae. Meanwhile, cyclo-(l-Pro-l-Leu) also promoted the accumulation of metabolites on the spoilage process of homogenate. S.baltica02 luxS mutant preliminarily proved that AI-2 might not play a signaling role in the spoilage. The present study suggested that the spoilage potential of S. baltica in P. crocea might be regulated by DKP-based quorum sensing.
authors.affiliation: College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, Zhejiang Province 310018, China. Electronic address: junlizhu0305@163.com.
authors.forename: Junli
authors.initials: J
authors.lastname: Zhu
authors.affiliation: College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, Zhejiang Province 310018, China.
authors.forename: Aifei
authors.initials: A
authors.lastname: Zhao
authors.affiliation: College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, Zhejiang Province 310018, China.
authors.forename: Lifang
authors.initials: L
authors.lastname: Feng
authors.affiliation: College of Life Science and Institute of Microbiology, Zhejiang University, Hangzhou, Zhejiang Province 310058, China.
authors.forename: Haichun
authors.initials: H
authors.lastname: Gao
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms / Q000254:growth & development*; D013437:Carbon-Sulfur Lyases / Q000235:genetics; D006862:Hydrogen Sulfide / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics; D010473:Perciformes / Q000382:microbiology*; D011700:Putrescine / Q000096:biosynthesis; D053038:Quorum Sensing / Q000235:genetics* / Q000502:physiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D020592:Shewanella / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D012097:Repressor Proteins; D015534:Trans-Activators; C064778:LuxR autoinducer binding proteins; D010089:Oxidoreductases, N-Demethylating; C023186:trimethylamine dehydrogenase; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria; D011700:Putrescine; D006862:Hydrogen Sulfide
keywords: Autoinducer 2; Cyclic dipeptides; Cyclo-(l-Pro-l-Leu); P. crocea; Quorum sensing; Shewanella baltica; Spoilage