Home About us MoEF Contact us Sitemap Tamil Website  
About Envis
Whats New
Microorganisms
Research on Microbes
Database
Bibliography
Publications
Library
E-Resources
Microbiology Experts
Events
Online Submission
Access Statistics

Site Visitors

blog tracking


 
International Journal of Food Microbiology
Vol. 192, 2015; Pages: 26-33

The involvement of bacterial quorum sensing in the spoilage of refrigerated Litopenaeus vannamei

Suqin Zhu, Haohao Wu, Mingyong Zeng, Zunying Liu, Ying Wang

College of Food Science and Engineering, Ocean University of China, 5 Yushan Road, Qingdao, Shandong Province 266003, China


Abstract

Quorum-sensing signals in refrigerated shrimp (Litopenaeus vannamei) undergoing spoilage were examined using bioreporter assays, thin-layer chromatography and gas chromatography–mass spectrometry, and the results revealed the presence of three types of autoinducers including acetylated homoserine lactones (AHLs) (i.e., N-hexanoyl-homoserine lactone, N-oxohexanoyl-homoserine lactone and N-octanoyl-homoserine lactone), autoinducer-2, and cyclic dipeptides (i.e., cyclo-(l-Pro-l-Leu), cyclo-(l-Leu-l-Leu) and cyclo-(l-Pro-l-Phe)). Autoinducer-2, rather than any AHL, was detected in extracts from pure cultures of the specific spoilage organisms (SSO), i.e., Shewanella putrefaciens (SS01) and Shewanella baltica (SA02). As for the cyclic peptides, only SA02 was determined to produce cyclo-(l-Pro-l-Leu). According to the transcription levels of LuxR (the master quorum-sensing regulator) in the SSO in response to exogenous autoinducers, the SSO could sense AHLs and cyclo-(l-Leu-l-Leu), rather than autoinducer-2, cyclo-(l-Leu-l-Leu) and cyclo-(l-Pro-l-Phe). In accordance with the results of LuxRexpression, the production of biofilm matrixes and extracellular proteases in the SSO was regulated by exogenous AHLs and cyclo-(l-Pro-l-Leu), rather than 4,5-dihydroxy-2,3-pentanedione (the autoinducer-2 precursor), cyclo-(l-Leu-l-Leu) and cyclo-(l-Pro-l-Phe). Exogenous N-hexanoyl-homoserine lactone and cyclo-(l-Pro-l-Leu) increased the growth rates and population percentages of the SSO in shrimp samples under refrigerated storage, and interestingly, exogenous 4,5-dihydroxy-2,3-pentanedione also increased the population percentages of the SSO in vivo by inhibiting the growth of the competing bacteria. However, according to the levels of TVB-N and the volatile organic components in the shrimp samples, exogenous 4,5-dihydroxy-2,3-pentanedione did not accelerate the shrimp spoilage process as N-hexanoyl-homoserine lactone and cyclo-(l-Pro-l-Leu) did. In summary, our results suggest that quorum sensing involves the spoilage of refrigerated Litopenaeus vannamei.

Keywords: Shrimp; Spoilage; Quorum sensing; Shewanella putrefaciens; Shewanella baltica


 

 

 
Copyright © 2005 ENVIS Centre ! All rights reserved
This site is optimized for 1024 x 768 screen resolution