Abstract
Some bacteria can modulate their spoilage potential by responding to environmental signaling molecules via the quorum sensing (QS) system. However, the ability of Pseudomonas fluorescens, the specific spoilage organism (SSO) of turbot, to response to environmental signaling molecules remains unclear. This study investigated the effects of six synthetic N-acyl homoserine lactones (AHLs) on typical behaviors mediated by QS in P. fluorescens, such as biofilm formation and extracellular protease activity. Total volatile basic nitrogen (TVB-N) was used as a spoilage indicator to evaluate quality changes in AHL-treated turbot filets during storage. The results confirm the enhancing effect of environmental AHLs on QS-dependent factors of P. fluorescens and quality deterioration of turbot filets, with C4-HSL and C14-HSL being the most effective. Moreover, the content decrease of exogenous AHLs was also validated by gas chromatography–mass spectrometry analysis. Further, changes in rhlR transcription levels in P. fluorescens suggest that this bacterium can sense environmental AHLs. Finally, molecular docking analysis demonstrates the potential interactions of RhlR protein with various exogenous AHLs. These findings strongly implicate environmental AHLs in turbot spoilage caused by P. fluorescens, suggesting preservation of turbot should not exclusively consider the elimination of SSO-secreted AHLs.
Highlights
Bacterial growth and metabolism results in aquatic food spoilage through protein degradation and formation of unacceptable volatile constituents, such as amines, alcohols, aldehydes, and sulfides (Gram and Dalgaard, 2002)
The results showed that the growth of P. fluorescens was significantly (P < 0.05) accelerated by shortening the lag phase in the presence of C4-HSL, C6-HSL, C8-HSL, C12-HSL, and C14HSL
This study validated the involvement of environmental acyl homoserine lactones (AHLs) on turbot spoilage via the promotion of quorum sensing (QS) phenotypes in P. fluorescens, which are required for fish spoilage
Summary
Bacterial growth and metabolism results in aquatic food spoilage through protein degradation and formation of unacceptable volatile constituents, such as amines, alcohols, aldehydes, and sulfides (Gram and Dalgaard, 2002). Recent studies have indicated that bacterial spoilage may be regulated by a cell density-dependent communication mechanism called quorum sensing (QS), which is based on the self-secretion and detection of QS signaling molecules (Fuqua et al, 1994; Gui et al, 2017; Zhao et al, 2017). Autoinducer Eavesdropping Influence Turbot Spoilage for food spoilage (such as extracellular proteases, lipases, pectases, and cellulases) or pathogenesis (such as biofilm formation, motility alteration, hemolysin production, and pyocyanin generation) when the concentration of these signaling molecules reaches a certain threshold level (Bai and Rai, 2011). Recent studies have found that the above signaling molecules are often detected in contaminated aquatic products (Li et al, 2016; Zhao et al, 2017). Additional work is still needed to explore the potential relationship between signaling molecule-based QS system and food spoilage
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