不同胁迫条件下产志贺毒素大肠杆菌生长及产毒能力异质性分析

Heterogeneity of growth and toxigenicity of Shiga toxin- producing Escherichia coli under different stress conditions

摘要:

【目的】本文旨在探究产志贺毒素大肠杆菌(Shiga toxin-producing Escherichia coli, STEC)在不同胁迫条件下的生长情况以及产毒状况的变化，为STEC菌株在胁迫压力下应激机制研究提供基础数据参考。【方法】选取3株STEC菌株分别在不同pH值、不同盐浓度、不同温度下进行适应性传代培养，使用一级生长模型Gompertz模型分析其在胁迫环境下的生长异质性；通过Vero细胞毒性实验分析胁迫条件下菌株的产毒状况。【结果】除了pH 5.0条件下的ST462菌株，在pH 5.0和9.0、较高盐浓度1.5% NaCl和2.5% NaCl以及低温10 ℃胁迫条件下STEC菌株都表现出最大比生长速率(μ_max)降低、迟缓期(λ)延长，差异显著(P<0.01)；不同胁迫条件下提取的STEC菌株毒素侵染细胞后测得的细胞存活率均低于对照最适条件，而pH 5.0条件下相反。【结论】STEC菌株在碱性、较高浓度盐以及低温环境胁迫压力下响应应激机制，生长虽受到抑制，但其所产毒素对Vero细胞造成的损伤加重，毒性增强。本研究通过胁迫环境下生长和产毒状况的异质性分析，将有助于全面了解STEC菌株应激反应下的生物学特性；对完善食品安全措施和食品加工过程中检测、杀菌、预防具有重要的指导意义。

Abstract:

[Objective] This paper aims to explore the growth and toxigenicity of Shiga toxin-producing Escherichia coli (STEC) under different stress conditions, and to provide basic data reference for the study of the stress response mechanism of STEC strains under stress. [Methods] Three STEC strains were selected for adaptive subculture at different pH values, different salt concentrations, and different temperatures, and their growth heterogeneity under stress was analyzed via the Gompertz model. The toxigenicity of the strains under stress was analyzed by the Vero cytotoxicity assay. [Results] Except the ST462 strain at pH 5.0, other STEC strains showed decrease in the maximum specific growth rate (μ_max) and extension of the lag period (λ) under stress conditions (pH 5.0 or 9.0, 1.5% NaCl or 2.5% NaCl, 10 ℃) (P<0.01). The viability of the cells treated with the toxins extracted from STEC strains under different stress conditions was lower than that under the optimal control conditions, while the opposite trend was observed at pH 5.0. [Conclusion] STEC strains activated the stress response mechanism under alkaline stress, higher salt concentrations, and low temperatures. Although the growth was inhibited, the toxins produced by the strains exposed to stress aggravated the damage to Vero cells, demonstrating increased toxicity. By analyzing the heterogeneity of the growth and toxigenicity in a stressful environment, this study helps to comprehensively understand the biological characteristics of STEC strains under stress and has guiding significance for improving the detection, sterilization, and prevention measures during food processing to ensure food safety.