Effect of Internalin InlJ of Listeria monocytogenes on Phage Sensitivity and Biofilm Formation

In order to explore the role and function of the inlJ gene of Listeria monocytogenes (Lm) in phage sensitivity and biofilm, the inlJ gene-deficient strain Lm NJ05-ΔinlJ was constructed by homologous recombination. The growth, adhesion and invasion characteristics of the defective strain were identified. The results showed that compared with the wide-type strain Lm NJ05, the adhesion and invasion of RAW264.7 cells by Lm NJ05-ΔinlJ were significantly reduced to 20.05% and 4.42%, respectively. The efficiency of plaque formation was enhanced by 2.72 folds and phage vB-LmoM-NJ05 had a stronger lytic activity on Lm NJ05-ΔinlJ. Phage vB-LmoM-NJ05 at titers of 10⁵ and 10⁸ PFU/mL could completely inhibit and remove the biofilm of Lm NJ05-ΔinlJ, respectively. Transcriptional analysis of biofilm formation-related genes showed that the transcriptional levels of the degU, agrA, agrD, luxS, yneA, recA and hpt genes were significantly decreased to nearly zero in the defective strain after interacting with phage vB-LmoM-NJ05. In conclusion, deletion of the inlJ gene can enhance the phage sensitivity of Lm, and down-regulate the ability of cell invasion and biofilm formation. Therefore, the inlJ gene not only regulate Lm but also affect its interaction with phage, which lays a foundation for the development and application of phage biocontrol.