There is an urgent need to discover biocontrol agents to control bacterial wilt. This study reports on a new lipopeptide-producing biocontrol strain FJAT-46737 and explores its lipopeptidic compounds, and this study investigates the antagonistic effects of these compounds. Based on a whole genome sequence analysis, the new strain FJAT-46737 was identified as Bacillus velezensis, and seven gene clusters responsible for the synthesis of bioactive secondary metabolites in FJAT-46737 were predicted. The antimicrobial results demonstrated that FJAT-46737 exhibited broad-spectrum antimicrobial activities in vitro against three bacteria and three fungi. Pot experiments showed that the control efficiencies for tomato bacterial wilt of the whole cultures, the 2-fold diluted supernatants and the crude lipopeptide of FJAT-46737 were 66.2%, 82.0%, and 96.2%, respectively. The above results suggested that one of the antagonistic mechanisms of FJAT-46737 was the secretion of lipopeptides consisting of iturins, fengycins and surfactins. The crude lipopeptides had significant antagonistic activities against several pathogens (including Ralstonia solanacearum, Escherichia coli and Fusarium oxysporum) and fengycins were the major antibacterial components of the lipopeptides against R. solanacearum in vitro. Furthermore, the rich organic nitrogen sources (especially yeast extracts) in the media promoted the production of fengycin and surfactin by FJAT-46737. The secretion of these two lipopeptides was related to temperature fluctuations, with the fengycin content decreasing by 96.6% and the surfactins content increasing by 59.9% from 20 °C to 40 °C. The optimal temperature for lipopeptide production by FJAT-46737 varied between 20 °C and 25 °C. The B. velezensis strain FJAT-46737 and its secreted lipopeptides could be used as new sources of potential biocontrol agents against several plant pathogens, and especially the bacterial wilt pathogen R. solanacearum.

中文翻译：

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新菌株velacensis velezensis FJAT-46737及其脂肽对番茄青枯病的生物防治。

迫切需要发现生物控制剂来控制细菌枯萎。这项研究报道了一种新的产生脂肽的生物防治菌株FJAT-46737，并探索了其脂肽化合物，并且该研究也研究了这些化合物的拮抗作用。基于全基因组序列分析，新菌株FJAT-46737被鉴定为velacensis velezensis，并预测了七个负责FJAT-46737生物活性次级代谢产物合成的基因簇。抗菌结果表明，FJAT-46737在体外对三种细菌和三种真菌表现出广谱抗菌活性。盆栽试验表明，FJAT-46737的整个培养液，2倍稀释的上清液和粗脂肽对番茄青枯病的防治效率分别为66.2％，82.0％和96.2％，分别。以上结果表明，FJAT-46737的拮抗机制之一是分泌由伊图林，丰霉素和表面活性素组成的脂肽。粗制脂肽对几种病原体（包括青枯雷尔氏菌，大肠杆菌和尖孢镰刀菌）具有显着的拮抗活性，风霉素是脂肽在体外对青枯菌的主要抗菌成分。此外，培养基中丰富的有机氮源（尤其是酵母提取物）通过FJAT-46737促进了丰霉素和表面活性素的生产。从20°C到40°C，这两个脂肽的分泌与温度波动有关，风霉素的含量下降了96.6％，表面活性素的含量上升了59.9％。FJAT-46737生产脂肽的最佳温度在20°C和25°C之间变化。velezensis B. velezensis菌株FJAT-46737及其分泌的脂肽可用作对抗几种植物病原体，尤其是细菌枯萎病菌青枯菌的潜在生物防治剂的新来源。