Shu Xiaomei, Singh Manavi, Karampudi Naga Bhushana Rao, Bridges David F, Kitazumi Ai, Wu Vivian C H, De Los Reyes Benildo G
Department of Plant and Soil Science, Texas Tech University, Lubbock, TX, United States.
Produce Safety and Microbiology Research, Western Regional Research Center, United States Department of Agriculture - Agricultural Research Service, Albany, CA, United States.
Front Microbiol. 2020 Jun 3;11:1122. doi: 10.3389/fmicb.2020.01122. eCollection 2020.
serotype O157:H7 is one of the major agents of pathogen outbreaks associated with fresh fruits and vegetables. Gaseous chlorine dioxide (ClO) has been reported to be an effective intervention to eliminate bacterial contamination on fresh produce. Although remarkable positive effects of low doses of ClO have been reported, the genetic regulatory machinery coordinating the mechanisms of xenobiotic effects and the potential bacterial adaptation remained unclear. This study examined the temporal transcriptome profiles of O157:H7 during exposure to different doses of ClO in order to elucidate the genetic mechanisms underlying bacterial survival under such harsh conditions. Dosages of 1 μg, 5 μg, and 10 μg ClO per gram of tomato fruits cause different effects with dose-by-time dynamics. The first hour of exposure to 1 μg and 5 μg ClO caused only partial killing with significant growth reduction starting at the second hour, and without further significant reduction at the third hour. However, 10 μg ClO exposure led to massive bacterial cell death at 1 h with further increase in cell death at 2 and 3 h. The first hour exposure to 1 μg ClO caused activation of primary defense and survival mechanisms. However, the defense response was attenuated during the second and third hours. Upon treatment with 5 μg ClO, the transcriptional networks showed massive downregulation of pathogenesis and stress response genes at the first hour of exposure, with decreasing number of differentially expressed genes at the second and third hours. In contrast, more genes were further downregulated with exposure to 10 μg ClO at the first hour, with the number of both upregulated and downregulated genes significantly decreasing at the second hour. A total of 810 genes were uniquely upregulated at the third hour at 10 μg ClO, suggesting that the potency of xenobiotic effects had led to potential adaptation. This study provides important knowledge on the possible selection of target molecules for eliminating bacterial contamination on fresh produce without overlooking potential risks of adaptation.
O157:H7血清型是与新鲜水果和蔬菜相关的病原体爆发的主要病原体之一。据报道，气态二氧化氯（ClO）是消除新鲜农产品上细菌污染的有效干预措施。尽管已报道低剂量ClO具有显著的积极作用，但协调异生物效应机制和潜在细菌适应性的遗传调控机制仍不清楚。本研究检测了O157:H7在暴露于不同剂量ClO期间的时间转录组谱，以阐明在这种恶劣条件下细菌存活的遗传机制。每克番茄果实中1μg、5μg和10μg ClO的剂量会产生不同的剂量-时间动态效应。暴露于1μg和5μg ClO的第一个小时仅导致部分细菌死亡，从第二个小时开始细菌生长显著减少，第三个小时没有进一步显著减少。然而，暴露于10μg ClO会导致1小时时大量细菌细胞死亡，2小时和3小时时细胞死亡进一步增加。暴露于1μg ClO的第一个小时会激活主要防御和存活机制。然而，在第二个小时和第三个小时防御反应减弱。用5μg ClO处理后，转录网络在暴露的第一个小时显示发病机制和应激反应基因大量下调，在第二个小时和第三个小时差异表达基因数量减少。相比之下，在第一个小时暴露于10μg ClO时更多基因进一步下调，在第二个小时上调和下调基因数量均显著减少。在10μg ClO处理的第三个小时共有810个基因独特地上调，表明异生物效应的效力已导致潜在的适应性。本研究提供了重要的知识，有助于在不忽视潜在适应风险的情况下选择消除新鲜农产品上细菌污染的靶分子。
