Elbakush Ahmed M, Trunschke Oliver, Shafeeq Sulman, Römling Ute, Gomelsky Mark
Department of Molecular Biology, University of Wyoming, Laramie, WY, United States.
Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.
Front Microbiol. 2024 Sep 16;15:1436476. doi: 10.3389/fmicb.2024.1436476. eCollection 2024.
The Pss exopolysaccharide (EPS) enhances the ability of the foodborne pathogen to colonize and persist on surfaces of fresh fruits and vegetables. Eradicating listeria within EPS-rich biofilms is challenging due to their increased tolerance to disinfectants, desiccation, and other stressors. Recently, we discovered that extracts of maple wood, including maple sap, are a potent source of antibiofilm agents. Maple lignans, such as nortrachelogenin-8'-O-β-D-glucopyranoside and lariciresinol, were found to inhibit the formation of, and promote the dispersion of pre-formed EPS biofilms. However, the mechanism remained unknown. Here, we report that these lignans do not affect Pss EPS synthesis or degradation. Instead, they promote EPS detachment, likely by interfering with an unidentified lectin that keeps EPS attached to the cell surfaces. Furthermore, the maple lignans inhibit the activity of sortase A (SrtA) . SrtA is a transpeptidase that covalently anchors surface proteins, including the Pss-specific lectin, to the cell wall peptidoglycan. Consistent with this, deletion of the gene results in Pss EPS detachment from listerial cells. We also identified several additional maple compounds, including epicatechin gallate, isoscopoletin, scopoletin, and abscisic acid, which inhibit SrtA activity and prevent biofilm formation. Molecular modelling indicates that, despite their structural diversity, these compounds preferentially bind to the SrtA active site. Since maple products are abundant and safe for consumption, our finding that they prevent biofilm formation in offers a viable source for protecting fresh produce from this foodborne pathogen.
Pss胞外多糖（EPS）增强了食源性病原体在新鲜水果和蔬菜表面定殖和持续存在的能力。由于富含EPS的生物膜对消毒剂、干燥和其他应激源的耐受性增强，根除其中的李斯特菌具有挑战性。最近，我们发现枫木提取物，包括枫糖浆，是抗生物膜剂的有效来源。已发现枫木木质素，如去甲rachelogenin - 8'-O-β-D-吡喃葡萄糖苷和落叶松脂醇，可抑制EPS生物膜的形成，并促进其预先形成的生物膜的分散。然而，其机制尚不清楚。在此，我们报告这些木质素不会影响Pss EPS的合成或降解。相反，它们可能通过干扰一种未知的凝集素促进EPS的脱离，该凝集素使EPS附着在细胞表面。此外，枫木木质素抑制分选酶A（SrtA）的活性。SrtA是一种转肽酶，可将包括Pss特异性凝集素在内的表面蛋白共价锚定到细胞壁肽聚糖上。与此一致，该基因的缺失导致Pss EPS从李斯特菌细胞上脱离。我们还鉴定了几种其他的枫木化合物，包括表儿茶素没食子酸酯、异东莨菪素、东莨菪素和脱落酸，它们抑制SrtA活性并防止生物膜形成。分子建模表明，尽管这些化合物结构多样，但它们优先结合到SrtA活性位点。由于枫木产品丰富且食用安全，我们发现它们可防止生物膜形成，这为保护新鲜农产品免受这种食源性病原体侵害提供了一个可行的来源。
