Phloem-limited bacterial “Candidatus Liberibacter” species are associated with incurable plant diseases worldwide. Antimicrobial treatments for these pathogens are challenging due to the difficulty of reaching the vascular tissue they occupy at bactericidal concentrations. Here, in vitro antimicrobial mechanisms of Zinkicide TMN110 (ZnK), a nonphytotoxic zinc oxide (ZnO)-based nanoformulation, were compared to those of bulk ZnO (b-ZnO) using as a model the only culturable species of the genus, Liberibacter crescens. Minimum bactericidal concentration (MBC) determination and time-kill assays showed that ZnK has a bactericidal effect against L. crescens, whereas b-ZnO is bacteriostatic. When ZnK was used at the MBC (150 ppm), its antimicrobial mechanisms included an increase in Zn solubility, generation of intracellular reactive oxygen species, lipid peroxidation, and cell membrane disruption; all of these were of greater intensity than those of b-ZnO. Inhibition of biofilms, which are important during insect vector colonization, was stronger by ZnK than by b-ZnO at concentrations between 2.5 and 10 ppm in batch cultures; however, neither ZnK nor b-ZnO removed L. crescens preformed biofilms when applied between 100 and 400 ppm. In microfluidic chambers simulating source-to-sink phloem movement, ZnK significantly outperformed b-ZnO in Zn mobilization and bactericidal activity against L. crescens planktonic cells in sink reservoirs. In microfluidic chamber assays assessing antibiofilm activity, ZnK displayed a significantly enhanced bactericidal activity against L. crescens individual attached cells as well as preformed biofilms compared to that of b-ZnO. The superior mobility and antimicrobial activity of ZnK in microenvironments make this formulation a promising product to control plant diseases caused by “Candidatus Liberibacter” species and other plant vascular pathogens.

中文翻译：

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Zinkicide 是一种基于 ZnO 的纳米制剂，在分批培养和模拟植物血管系统的微流控室中具有针对新月自由杆菌的杀菌活性。


韧皮部限制的细菌“ Candidatus Liberibacter”物种与全世界无法治愈的植物病害有关。对这些病原体的抗菌治疗具有挑战性，因为难以以杀菌浓度到达它们所占据的血管组织。在这里，使用新月自由杆菌属唯一可培养的物种作为模型，将 Zinkicide TMN110 (ZnK)（一种无植物毒性的氧化锌 (ZnO) 基纳米制剂）的体外抗菌机制与散装 ZnO (b-ZnO) 的抗菌机制进行了比较。最低杀菌浓度(MBC)测定和时间杀灭试验表明，ZnK对新月杆菌具有杀菌作用，而b-ZnO则具有抑菌作用。当 ZnK 用于 MBC（150 ppm）时，其抗菌机制包括增加 Zn 溶解度、产生细胞内活性氧、脂质过氧化和细胞膜破坏；所有这些都比 b-ZnO 具有更高的强度。在分批培养中，浓度为 2.5 至 10 ppm 的 ZnK 对生物膜的抑制作用比 b-ZnO 更强，生物膜在昆虫媒介定植过程中非常重要。然而，当浓度在 100 至 400 ppm 之间时，ZnK 和 b-ZnO 都无法去除新月杆菌预先形成的生物膜。在模拟源到汇韧皮部运动的微流体室中，ZnK 在锌动员和对汇库中的L. crescens浮游细胞的杀菌活性方面显着优于 b-ZnO。在评估抗生物膜活性的微流体室测定中，ZnK 显示出显着增强的针对L. 与 b-ZnO 相比，新月形单个附着细胞以及预形成的生物膜。 ZnK 在微环境中卓越的流动性和抗菌活性使该配方成为控制由“ Candidatus Liberibacter”物种和其他植物维管病原体引起的植物病害的有前途的产品。