Listeria monocytogenes is a pathogenic bacterium that causes listeriosis through consumption of contaminated food. The bacterium survives under various conditions and forms persistent biofilms. B. subtilis PS-216 is a probiotic strain that produces various antimicrobial substances and has been shown to act antagonistically against various enterobacteria. The aim of this study was to determine the effect of B. subtilis and its products on the survival, adhesion, and biofilm of L. innocua, a nonpathogenic alternative to L. monocytogenes that does not require work in BSL2 laboratories. In this study, we constructed double-deletion mutants ΔaprE ΔcomA, ΔsboA ΔcomA, and ΔppsB ΔcomA, as well as stains with reporter fusions PsboA-yfp, Ppps-yfp, and PaprE-gfp. Gene expression was monitored using a fluorescence spectrometer, while the effects of
B. subtilis strains and their cell-free supernatants on the survival, adhesion, and biofilms of L. innocua were studied using a co-cultivation method. The effect of B. subtilis
PS-216 wild-type on L. innocua biofilms was investigated by confocal microscopy. The results demonstrated the crucial role of the functional ComQXPA system, while subtilisin E, subtilozin A, and plipastatin exhibited varying degrees of effect on the survival, adhesion, and biofilms of L. innocua. Interestingly, inhibition of plipastatin production enhanced the antibiofilm activity of B. subtilis, which warrants further investigation. This work demonstrated an antagonistic relationship between B. subtilis and L. innocua and the potential for its use in controlling the pathogenic bacterium; however, further experiments will be needed in the future.
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