National Reference Laboratory for Campylobacter, Department of Biological Safety, German Federal Institute for Risk Assessment, 12277 Berlin, Germany.
Int J Mol Sci. 2021 Sep 21;22(18):10169. doi: 10.3390/ijms221810169.
has a large adaptive potential due to enormous genetic exchange. Factors regulating natural transformation in this food-borne pathogen are largely unknown but of interest for the application of sustained reduction strategies in the food-processing industry. Using a single cell DNA uptake assay, we visualized that recognition of methylated DNA was essential for the first step of DNA uptake into a DNase resistant state. Transformation rates using a resistance marker correlated with the fraction of competent bacteria, harboring one to maximally four locations of active DNA uptake, not necessarily being located at the cell pole. Competence developed with rising pH between 6.5 and 7.5 under microaerobic conditions and was nearly insensitive towards growth temperatures between 32 °C and 42 °C, CO concentrations ranging from 0 to 50% and growth rates. However, competence development was abolished at pH 5 or under aerobic stress conditions, in which the bacteria ceased growth but fully survived. The DNA uptake machinery in competent bacteria shut down at slightly acidic pH and was reversibly switched on upon neutralization. It was dependent on the proton motive force and, in contrast to competence development, slightly enhanced under aerobic conditions. The results suggest that natural transformation in occurs in the neutral and microaerobic intestinal environment for enhanced genetic diversity and pre-adaption before host switch. In addition, highly competent bacteria might be shed into the environment, still able to acquire genetic material for increased survival.
由于巨大的遗传交换，具有很大的适应潜力。调节这种食源性病原体自然转化的因素在很大程度上是未知的，但对于食品加工行业持续减少策略的应用很有意义。我们使用单细胞 DNA 摄取测定法，直观地表明，识别甲基化 DNA 对于 DNA 摄取到抗 DNA 酶状态的第一步是必不可少的。使用抗性标记的转化率与感受态细菌的分数相关，这些细菌携带一个到最多四个活跃的 DNA 摄取位置，不一定位于细胞极。在微需氧条件下，pH 值在 6.5 到 7.5 之间上升时，会产生感受态，并且对 32°C 到 42°C 之间的生长温度、CO 浓度（0 到 50%）和生长速率几乎不敏感。然而，在 pH 值为 5 或有氧应激条件下，感受态的发育被废除，在这种条件下，细菌停止生长但完全存活。感受态细菌中的 DNA 摄取机制在酸性 pH 值下关闭，并在中和时可逆地打开。它依赖于质子动力势，与感受态发育相反，在有氧条件下略有增强。研究结果表明，在中性和微需氧的肠道环境中发生自然转化，以增强遗传多样性和宿主转换前的预先适应。此外，高感受态细菌可能会被释放到环境中，仍然能够获得遗传物质以提高生存能力。
