Use of whole-genome analysis to study the effect of various quorum-sensing inhibitors on the biofilm formation of Lactobacillus fermentum

To explore the effects of different quorum sensing inhibitors (QSIs) on the biofilm formation of Lactobacillus fermentum, a high-production signal molecule AI-2 screened by the research group, was taken as the research object and subjected to various QSIs. Three QSIs, namely 100 μmol/L d-galactose, 200 μmol/L d-ribose, and furanone, could inhibit the AI-2 activity of L. fermentum and the biofilm formation in a certain concentration range but not significantly affect the growth of the strain. Scanning electron microscopy and fluorescence microscopy revealed that each QSI did not significantly affect the bacterial cell morphology in planktonic and biofilm states at the optimal inhibitory final concentration, although they reduced the adhesion of the strain. The expression of luxS, a key gene of quorum sensing, was downregulated. When biofilm production increased, QSIs were added, and the activity of the AI-2 was consistent with the change in biofilm production. Whole-genome technology revealed that QSIs inhibited the expression of the luxS, resulting in restriction of pyruvate synthesis and downregulation of the expression of genes such as gapA, pgmB, ribBA, and ribF, which in turn affected the transport and metabolism of carbohydrates and coenzymes in the strain and ultimately reduced the biofilm formation of L. fermentum.