Changes in cell membrane properties and phospholipid fatty acids of bacillus subtilis induced by polyphenolic extract of Sanguisorba officinalis L

Sanguisorba officinalis L. (family Rosaceae, subfamily Rosoideae) is a plant found throughout Southern Europe, Northern Africa, and Eastern Asia. This study demonstrated the antibacterial activity of a purified polyphenolic extract (PPE) from S. officinalis L. against Bacillus subtilis using growth inhibitory and apoptosis assays, and investigated the antibacterial mechanism responsible for changes in cell membrane properties. Fourier transform infrared spectroscopy suggested that PPE altered the cell wall and membrane properties of B. subtilis. Further determination of cell membrane integrity and permeability revealed that B. subtilis membrane integrity was more severely damaged by PPE at the minimum inhibitory concentration (MIC) than at the minimum bactericidal concentrati on (MBC). Instead, PPE at the MBC reduced cell membrane fluidity by significantly decreasing the proportion of anteiso- and iso-branched phospholipid fatty acids (PLFAs) from 64.17 ± 0.28% and 27.23 ± 0.03% in the control to 5.57 ± 1.06% and 6.00 ± 1.40%, respectively (P < 0.001). Scanning electron microscopy revealed different effects of PPE on cell morphology, demonstrating that, at the MIC and MBC, PPE exerted antibacterial activity by disrupting the cell membrane and reducing cell membrane fluidity, respectively. Consequently, this study elucidated changes in the bacterial membrane due to exposure to PPE and its potential use as an antimicrobial agent. PRACTICAL APPLICATION: The abuse of synthetic chemical preservatives raises food safety concerns; however, plant-derived polyphenolic compounds may be a safe and effective alternative. This study demonstrated the strong antibacterial activity of a purified polyphenolic extract (PPE) of Sanguisorba officinalis L. and revealed its antibacterial mechanism against Bacillus subtilis, suggesting that it may provide a useful antimicrobial agent in food industry applications.

Keywords: Bacillus subtilis; Sanguisorba officinalis L; antibacterial mechanism; phospholipid fatty acids; polyphenol.