Antibacterial and Antibiofilm Efficacies of Cell-Free Supernatant of Dubosiella newyorkensis Against Pseudomonas fluorescens and Its Application in Food Systems

<i>Pseudomonas fluorescens</i> is a primary spoilage bacterium in aquatic products. Due to its strong ability to adhere to surfaces and form persistent biofilm, it poses a persistent challenge to food safety. Therefore, developing strategies to effectively inhibit biofilm formation holds significant research value. <i>Dubosiella newyorkensis</i>, a recently identified probiotic, has gained growing attention for its distinctive physiological features and potential functional benefits. Although various probiotic-derived cell-free supernatants (CFSs) have been explored for food preservation, the application of <i>D. newyorkensis</i> CFS against aquatic spoilage bacteria, and particularly its specific mechanism against <i>P. fluorescens</i> biofilm, has not been previously reported. Increasing evidence indicates that CFS from probiotic can influence microbial behavior, including biofilm development. In this study, we investigated the ability of <i>D. newyorkensis</i> CFS to inhibit <i>P. fluorescens</i> biofilm formation. The CFS treatment impaired bacterial growth and motility, lowered surface hydrophobicity, reduced self aggregation, and consequently hindered biofilm formation. Furthermore, CFS markedly decreased bacterial adhesion to food and contact surfaces. RT-qPCR analysis revealed that key genes associated with biofilm regulation were also significantly suppressed. Taken together, these results demonstrate that <i>D. newyorkensis</i> CFS exerts both antibacterial and antibiofilm effects against <i>P. fluorescens</i>. These findings provide a sound basis for exploring its application as a natural biopreservative to enhance the microbial safety and extend the shelf life of aquatic food products.