The present study investigated the antibacterial mechanism, control efficiency, and nontarget toxicity of actinomycin X₂ (Act-X₂) against Xanthomonas citri subsp. citri (Xcc) for the first time. Act-X₂ almost completely inhibited the proliferation of Xcc in the growth curve assay at a concentration of 0.25 MIC (minimum inhibitory concentration, MIC = 31.25 μg/mL). This inhibitory effect was achieved by increasing the production of reactive oxygen species (ROS), blocking the formation of biofilms, obstructing the synthesis of intracellular proteins, and decreasing the enzymatic activities of malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) of Xcc. Molecular docking and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis results indicated that Act-X₂ steadily bonded to the RNA polymerase, ribosome, malate dehydrogenase, and succinate dehydrogenase to inhibit their activities, thus drastically reducing the expression levels of related genes. Act-X₂ showed far more effectiveness than the commercially available pesticide Cu₂(OH)₃Cl in the prevention and therapy of citrus canker disease. Furthermore, the nontarget toxicity evaluation demonstrated that Act-X₂ was not phytotoxic to citrus trees and exhibited minimal toxicity to earthworms in both contact and soil toxic assays. This study suggests that Act-X₂ has the potential as an effective and environmentally friendly antibacterial agent.

中文翻译：

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放线菌素X2对柑橘黄单胞菌的抗菌机制、防治效果及非靶点毒性评价 柑橘

_{本研究探讨了放线菌素 X 2} (Act-X ₂ ) 对柑橘黄单胞菌亚种的抗菌机制、防治效果和非靶标毒性。citri (Xcc) 第一次。在生长曲线测定中， Act-X ₂在0.25 MIC（最低抑制浓度，MIC = 31.25 μg/mL）浓度下几乎完全抑制Xcc的增殖。这种抑制作用是通过增加活性氧（ROS）的产生、阻断生物膜的形成、阻碍细胞内蛋白质的合成以及降低Xcc的苹果酸脱氢酶（MDH）和琥珀酸脱氢酶（SDH）的酶活性来实现的。分子对接和定量逆转录聚合酶链反应（qRT-PCR）分析结果表明，Act-X ₂稳定地与RNA聚合酶、核糖体、苹果酸脱氢酶和琥珀酸脱氢酶结合，抑制其活性，从而大幅降低相关蛋白的表达水平。基因。Act-X ₂在预防和治疗柑橘溃疡病方面表现出比市售农药 Cu ₂ (OH) _{3 Cl 更有效的效果。}此外，非靶标毒性评估表明，Act-X ₂对柑橘树不具有植物毒性，并且在接触和土壤毒性测定中对蚯蚓的毒性极小。这项研究表明 Act-X ₂有潜力成为一种有效且环保的抗菌剂。