Bacillus methylotrophicus DR-08 exhibited strong antibacterial activity against Ralstonia solanacearum, a causal agent of tomato bacterial wilt. This study aimed to identify the antibacterial metabolites and evaluate the efficacy of the strain as a biocontrol agent for tomato bacterial wilt. A butanol extract of the DR-08 broth culture completely inhibited the growth of 14 phytopathogenic bacteria with minimum inhibitory concentration (MIC) values of 1.95-500 μg/mL. R. solanacearum was highly sensitive to the DR-08 extract, with an MIC value of 12.62 μg/mL. Two antibacterial metabolites were isolated and identified as difficidin and oxydifficidin derivatives through bioassay-guided fractionation and instrumental analyses. Both metabolite derivatives inhibited the growth of most of the phytopathogenic bacteria tested and the oxydifficidin derivatives generally presented a stronger antibacterial activity than the difficidin derivatives. A 30% suspension concentrate of DR-08, at a 500-fold dilution, effectively suppressed the development of tomato bacterial wilt in pot and field experiments. It also effectively reduced the development of bacterial leaf spot symptoms on peach and red pepper. The results of this study suggests that B. methylotrophicus DR-08 can be utilized as a biocontrol agent for various bacterial plant diseases including tomato bacterial wilt.

中文翻译：

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氧化艰难梭菌和产艰难梭菌的甲基营养芽孢杆菌 DR-08 对番茄青枯病的生物防治

甲基营养芽孢杆菌 DR-08 对番茄青枯病的病原体 Ralstonia solanacearum 表现出很强的抗菌活性。本研究旨在鉴定抗菌代谢物并评估该菌株作为番茄青枯病生物防治剂的功效。DR-08 肉汤培养物的丁醇提取物完全抑制了 14 种植物病原菌的生长，最小抑制浓度 (MIC) 值为 1.95-500 μg/mL。R. solanacearum 对 DR-08 提取物高度敏感，MIC 值为 12.62 μg/mL。通过生物测定引导的分级分离和仪器分析，分离出两种抗菌代谢物并鉴定为 difficidin 和 oxydifficidin 衍生物。两种代谢物衍生物均抑制了大多数测试的植物病原菌的生长，并且氧化艰难梭菌素衍生物通常比艰难梭菌素衍生物表现出更强的抗菌活性。30% 的 DR-08 悬浮浓缩物，稀释 500 倍，在盆栽和田间试验中有效抑制了番茄青枯病的发展。它还有效地减少了桃子和红辣椒上细菌性叶斑病症状的发展。该研究的结果表明，甲基营养型 B.methylotrophicus DR-08 可用作包括番茄青枯病在内的各种细菌性植物病害的生物防治剂。在盆栽和田间试验中有效抑制了番茄青枯病的发展。它还有效地减少了桃子和红辣椒上细菌性叶斑病症状的发展。该研究的结果表明，甲基营养型 B.methylotrophicus DR-08 可用作包括番茄青枯病在内的各种细菌性植物病害的生物防治剂。在盆栽和田间试验中有效抑制了番茄青枯病的发展。它还有效地减少了桃子和红辣椒上细菌性叶斑病症状的发展。该研究的结果表明，甲基营养型 B.methylotrophicus DR-08 可用作包括番茄青枯病在内的各种细菌性植物病害的生物防治剂。