Bacillus amyloliquefaciens X030 (BaX030) has broad-spectrum antibacterial activity against the fish pathogens Aeromonas hydrophila and Aeromonas veronii. To improve its antibacterial effect, BaX030 was subjected to compound mutagenesis of atmospheric and room temperature plasma (ARTP) and nitrosoguanidine (NTG). The results showed that, compared with the original strain, the production of macrolactin A and oxydifficidin in mutated strain N-11 increased to 39 % and 268 %, respectively. The re-sequencing analysis suggested that there were SNPs and InDels in the gene clusters focused on the sucrose utilization pathway, glycolysis pathway and fatty acid synthesis pathway. Scanning electron microscopy revealed that strain N-11 became thin and long. The qRT-PCR results indicated that the expression of immune factors in the liver or kidney tissue of grass carp increased after feeding with N-11. H&E staining and protection experiments also showed that the mortality and surface symptoms of grass carp infected by the two pathogens were significantly reduced. The study identified a probiotic strain with potential application value in aquaculture production and provided a new strategy for the discovery of new strains with higher antibacterial biological activity.

解淀粉芽孢杆菌X030 (BaX030) 对鱼类病原体嗜水气单胞菌和维罗气单胞菌具有广谱抗菌活性. 为提高其抗菌效果，BaX030进行了常温常温等离子体（ARTP）和亚硝基胍（NTG）的复合诱变。结果表明，与原始菌株相比，突变菌株N-11中macrolactin A和oxydifficidin的产量分别增加了39%和268%。重测序分析表明，基因簇中存在SNPs和InDels，主要集中在蔗糖利用途径、糖酵解途径和脂肪酸合成途径。扫描电子显微镜显示应变 N-11 变细变长。qRT-PCR结果表明，饲喂N-11后草鱼肝脏或肾脏组织中免疫因子的表达增加。H＆E染色和保护实验还表明，两种病原菌感染草鱼的死亡率和表面症状均显着降低。该研究鉴定了一种在水产养殖生产中具有潜在应用价值的益生菌菌株，为发现具有更高抗菌生物活性的新菌株提供了新的策略。