Boura Marcia, Yilmaz Topcam Mahide M, Spiteri David, Bruschi Carolina, Valdramidis Vasileios, Karatzas Kimon A G
Department of Food and Nutritional Sciences, University of Reading, Reading, RG6 6AD, United Kingdom.
Department of Food Sciences and Nutrition, Faculty of Health Sciences, University of Malta, Msida, MSD 2080, Malta.
J Appl Microbiol. 2025 Jul 1;136(7). doi: 10.1093/jambio/lxaf173.
The work aimed at investigating a possible role of sigB in catalase transcription and activity in Listeria monocytogenes. Furthermore, we also aimed to investigate whether sigB upregulation during the exponential phase, due to acid or salt adaptation, could result in hypersensitivity to oxidative stress. Finally, we investigated how this discovery could be used in the wider concept of Hurdle Technology through combination of different stresses.
Listeria monocytogenes 10403S WT and ΔsigB strains were grown aerobically, and catalase transcription and activity were assessed at different growth stages. Catalase transcription peaked at 6 h of growth in both strains, with ΔsigB showing higher levels. Subsequently, from 8 to 10 h, a major drop to similarly low levels occurred for both strains. However, catalase activity peaked 2 h later (at 8 h of growth) than transcription and remained higher in ΔsigB beyond this point. To evaluate stress adaptation, exponential-phase cells were exposed to sub-lethal acidic conditions (pH 4.5; HCl) or salt (0.5 mol l-1 NaCl) and later subjected to H2O2 or sonication (tested only with acid). Adaptation increased sensitivity in the wild type (WT) but not in ΔsigB, underpinning the negative role of sigB upregulation. Acid adaptation reduced catalase activity in both strains, explaining the reduced oxidative stress resistance, although salt adaptation did not affect catalase activity. After adaptation to acid or salt, application of oxidative stress without removing the initial adaptation stresses resulted in a higher synergistic effect in both WT and ΔsigB.
The above synergistic effects are important for our understanding of listerial oxidative stress resistance and optimization of relevant oxidative stress decontamination processes (e.g. oxidative compounds, ultrasound, and plasma treatments) but also virulence.
本研究旨在探究sigB在单核细胞增生李斯特菌过氧化氢酶转录及活性中可能发挥的作用。此外，我们还旨在研究指数生长期因酸或盐适应导致的sigB上调是否会使其对氧化应激更加敏感。最后，我们研究了如何通过不同应激因素的组合，将这一发现应用于更广泛的栅栏技术概念中。
将单核细胞增生李斯特菌10403S野生型和ΔsigB菌株进行需氧培养，并在不同生长阶段评估过氧化氢酶的转录及活性。两种菌株的过氧化氢酶转录在生长6小时时均达到峰值，ΔsigB菌株的转录水平更高。随后，从8小时到10小时，两种菌株的转录水平均大幅下降至相似的低水平。然而，过氧化氢酶活性的峰值比转录峰值晚2小时（在生长8小时时）出现，并且在此之后ΔsigB菌株中的过氧化氢酶活性一直更高。为了评估应激适应情况，将指数生长期的细胞暴露于亚致死酸性条件（pH 4.5；HCl）或盐（0.5 mol l-1 NaCl）下，随后施加过氧化氢或超声处理（仅对酸处理进行了测试）。适应过程增加了野生型（WT）的敏感性，但对ΔsigB菌株没有影响，这支持了sigB上调的负面作用假设。酸适应降低了两种菌株的过氧化氢酶活性，这解释了氧化应激抗性的降低，尽管盐适应并未影响过氧化氢酶活性。在适应酸或盐之后，在不消除初始适应应激的情况下施加氧化应激，在WT和ΔsigB菌株中均产生了更高的协同效应。
上述协同效应对于我们理解李斯特菌的氧化应激抗性以及优化相关的氧化应激去污过程（如氧化化合物、超声和等离子体处理）具有重要意义，同时也有助于理解其毒力。
