College of Food Science, Southwest University, Chongqing, China.
J Appl Microbiol. 2019 Dec;127(6):1741-1750. doi: 10.1111/jam.14433. Epub 2019 Oct 3.
Lactic acid is a natural antimicrobial in food industry, and also exists in fermented food. It was reported that sublethally injured Escherichia coli could survive in acidic conditions. When conditions become advantageous, injured E. coli can restore physiological function, which is a potential threat in food industry. Recovery is a necessary step for discriminating injured bacteria, but the resuscitation mechanism of injured bacteria is still unknown.
In our study, sublethal lactic acid treatment (pH 4·2, 60 min) posed oxidative stress on E. coli by decrease of superoxide dismutase (SOD) activity and overproduction of reactive oxygen species (ROS). Zinc with low concentration (1·0 mmol l ) significantly increased the recovery ratio of injured E.coli induced by lactic acid. The recovery ratios of injured cell in minimal A medium (minA) with 1·0 mmol l zinc reached to that with 3·0 mmol l catalase (CAT). Conversely, the addition of zinc chelator N, N, N', N'-tetrakis (2-pyridylmethyl) decreased the recovery ratio. Zinc accelerated resuscitation of injured E. coli by improving SOD activity, and decreasing ROS production. Deletion of sodC encoding Cu/ZnSOD, katE/katG encoding CAT or regulating gene rpoS significantly decreased the recovery ratio. Among all of the mutants in this study, ΔrpoS and ΔsodC showed the lowest recovery ratio, which means they played significant roles in the process of resuscitation.
We provided direct evidence that zinc mediated resuscitation of lactic acid-injured E. coli by relieving oxidative stress. Zinc can be used as a low-cost and effective agent to improve recovery ratio and detection efficiency of injured bacteria.
Antibacterial agents are a challenge for bacteria, but bacteria can survive as a sublethally injured state under stresses. Using injured E. coli induced by lactic acid as a model organism, we validated the significant role of zinc on resuscitation of injured cells.
乳酸是食品工业中的一种天然抗菌剂，也存在于发酵食品中。据报道，亚致死剂量损伤的大肠杆菌可以在酸性条件下存活。当条件变得有利时，受损的大肠杆菌可以恢复生理功能，这在食品工业中是一个潜在的威胁。复苏是区分受损细菌的必要步骤，但受损细菌的复苏机制尚不清楚。
在本研究中，亚致死浓度乳酸处理（pH4.2，60min）通过降低超氧化物歧化酶（SOD）活性和产生过量的活性氧物质（ROS）对大肠杆菌造成氧化应激。低浓度锌（1.0mmol·l）显著增加了由乳酸诱导的受损大肠杆菌的恢复比例。在最低 A 培养基（minA）中添加 1.0mmol·l 锌的受损细胞的恢复比例达到了添加 3.0mmol·l 过氧化氢酶（CAT）的水平。相反，添加锌螯合剂 N，N，N′，N′-四（2-吡啶基甲基）降低了恢复比例。锌通过提高 SOD 活性和降低 ROS 产生来加速受损大肠杆菌的复苏。sodC 编码 Cu/ZnSOD、katE/katG 编码 CAT 或调节基因 rpoS 的缺失显著降低了恢复比例。在所研究的所有突变体中，ΔrpoS 和 ΔsodC 显示出最低的恢复比例，这意味着它们在复苏过程中发挥了重要作用。
我们提供了直接证据表明锌通过缓解氧化应激介导乳酸损伤大肠杆菌的复苏。锌可以作为一种低成本、有效的制剂，提高受损细菌的恢复比例和检测效率。
抗菌剂对细菌是一个挑战，但细菌可以在应激下作为亚致死损伤状态存活。使用乳酸诱导的受损大肠杆菌作为模型生物，我们验证了锌对受损细胞复苏的重要作用。
