RNA-seq-based transcriptomic analysis of AHL-induced biofilm and pyocyanin inhibition in Pseudomonas aeruginosa by Lactobacillus brevis

Quorum sensing (QS) regulates hundreds of genes in Pseudomonas aeruginosa, and many of which encode extracellular virulence factors. Lactobacillus as a probiotic has been verified to inhibit pathogenesis in P. aeruginosa via quenching QS. The objective of this study was to investigate mechanism of the QS quenching function of Lactobacillus via analyzing the gene expression by transcriptome. We previously isolated a Lactobacillus brevis strain 3M004 from an aquafeed and identified the strain has the function of degrading QS molecular AHL (OC12-HSL). The result showed that 3M004 cells/lysate inhibited biofilm and pyocyanin production of P. aeruginosa PA002. The biofilm inhibition rates were 16.92% and 33.0% after treatment by 1 and 2 mg/mL 3M004 lysate, respectively, and the rates for pyocyanin inhibition were 25.16% and 30.75%, respectively. Transcriptomic analysis showed that down-regulation of genes of LasA and LasB in PA002 was essential in regulating the QS system. The biofilm decrease of PA002 seems not only resulted from gene biosynthesizing of polysaccharides but also from other genes regulating components biosynthesis. Pyocyanin biosynthesis appears to be inhibited by down-regulating the key gene of PhzAB on the nonreversing action from chorismite to pyocyanin.