稻米内生贝莱斯芽孢杆菌BR-1的安全性评估

Safety Assessment of Endophytic Bacillus velezensis BR-1 in Rice

摘要:

目的 对从稻米中分离的一株稻米内生贝莱斯芽孢杆菌（Bacillus velezensis， B. velezensis）BR-1进行安全性评估。方法 在全基因组测序的基础上，应用综合抗生素耐药数据库（CARD）和毒力因子数据库（VFDB）对BR-1的抗生素耐药基因和毒力基因进行注释，同时对BR-1进行抗生素药敏试验和溶血试验，并利用KEGG数据库注释贝莱斯芽孢杆菌BR-1与益生菌相关的基因。结果 该稻米内生贝莱斯芽孢杆菌BR-1总碱基对为1 071 550 432 bp，平均GC占比46.3%，包含4 027个蛋白质编码基因，含有14个CRISPR-Cas；不含有编码溶血素BL（Hbl）、非溶血性肠毒素（Nhe）、肠毒素（细胞毒素K）和催吐毒素（cereulide-Ces）等毒素基因；KEGG数据库注释到可耐酸、耐高温、耐胆盐等具有良好的胃肠耐受性、抗氧化活性和优异益生菌特性的基因；预测到菌株BR-1含有2个耐药基因vmlR和clbA，对9种抗生素高度敏感且不含有耐药质粒。结论 贝莱斯芽孢杆菌BR-1不含有编码毒素的基因，不具有广谱耐药性，不具有溶血活性，含有益生菌特性相关的基因，符合GB/T 41728—2022《微生物肥料质量安全评价通用准则》的安全性要求，可以作为微生物肥料。

Abstract:

Objective The aim of the study is to evaluate the safety of an endophytic strain Bacillus velezensis (B. velezensis） BR-1 isolated from rice.Method The Comprehensive Antibiotic Resistance Database (CARD) and the Virulence Factor Database (VFDB) were employed to annotate the antibiotic resistance genes and virulence genes, respectively, of BR-1 based on the whole genome sequence. The antibiotic sensitivity test and hemolysis test of BR-1 were performed, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) was used to annotate the genes related to probiotic properties of B. velezensis BR-1.Result The total genome length of B. velezensis BR-1 was 1 071 550 432 bp, with an average GC ratio of 46.3%, containing 4 027 protein-coding genes and 14 CRISPR-Cas. It did not contain genes encoding toxins such as hemolysin BL (Hbl), non-hemolytic enterotoxin (Nhe), enterotoxin (cytotoxin K), and deoxynivalenol (cereulide-Ces). The KEGG annotation revealed genes with good gastrointestinal tolerance, antioxidant activity, and excellent probiotic properties such as acid tolerance, high temperature tolerance, and bile salt tolerance. It was predicted that strain BR-1 contained two antibiotic resistance genes vmlR and clbA. This strain was highly sensitive to 9 antibiotics and did not contain drug-resistant plasmids.Conclusion B. velezensis BR-1 does not contain genes encoding toxins or have broad-spectrum antibiotic resistance and hemolytic activity. It carries genes related to probiotic properties, which meets the safety requirements specified in the General Criteria for Quality and Safety Evaluation of Microbial Fertilizer (GB/T 41728—2022), and can be safely applied as microbial fertilizer.