The mechanisms of condensed tannins inhibit Pediococcus pentosaceus

Abstract

Abstract Background The antibacterial mechanisms of action of condensed tannins (CTs) obtained from tea are well known. However, the antibacterial mechanism of CTs from legumes, such as sainfoin, against to Pediococcus pentosaceus was still unclear. Using Pediococcus pentosaceus SF11 as a model organism, this study investigated the antibacterial mechanism of CTs (extract from sainfoin by 70% acetone aqueous solution). Methods The mechanism of CTs against Pediococcus pentosaceus was investigated though determined the minimal inhibitory concentration (MIC) of CTs, effects of CTs on cell membrane, scanning and transmission electron microscopy analysis and global transcriptome analysis, et al. Results The results showed that CTs decreased the activities of enzymes such as lactic dehydrogenase, and inhibited the pentose phosphate (PP)/glycolytic pathway. The content of hydrogen peroxide produced by CTs was increased in P. pentosaceus SF11, and antibacterial activity partly occurred due to this hydrogen peroxide. The global transcriptome analysis showed that CTs upregulated the expression of 187 genes, most of which were involved in hypothetical protein, followed by the PTS (phosphotransferase system) system, while three genes were involved in oxidative stress. The expression of 161 genes was downregulated, most of which were involved in the phosphate ABC transporter system. Conclusion These findings suggest that the mechanism of antibacterial action of sainfoin CTs mainly operates through the inhibition of protease activity, and is partly associated with oxidative stress induced by hydrogen peroxide. Graphical Abstract