DataSheet_1_Elucidating the genomic history of commercially used Bacillus thuringiensis subsp. tenebrionis strain NB176.docx

Bacillus thuringiensis subsp. tenebrionis (Btt) produces a coleopteran-specific crystal protoxin protein (Cry3Aa δ-endotoxin). After its discovery in 1982, the strain NB125 (DSM 5526) was eventually registered in 1990 to control the Colorado potato beetle (Leptinotarsa decemlineata). Gamma-irradiation of NB125 resulted in strain NB176-1 (DSM 5480) that exhibited higher cry3Aa production and became the active ingredient of the plant protection product Novodor® FC. Here, we report a comparative genome analysis of the parental strain NB125, its derivative NB176-1 and the current commercial production strain NB176. The entire genome sequences of the parental and derivative strains were deciphered by a hybrid de novo approach using short (Illumina) and long (Nanopore) read sequencing techniques. Genome assembly revealed a chromosome of 5.4 to 5.6 Mbp and six plasmids with a size range from 14.9 to 250.5 kbp for each strain. The major differences among the original NB125 and the derivative strains NB176-1 and NB176 were an additional copy of the cry3Aa gene, which translocated to another plasmid as well as a chromosomal deletion (~ 178 kbp) in NB176. The assembled genome sequences were further analyzed in silico for the presence of virulence and antimicrobial resistance (AMR) genes.

苏云金杆菌拟步甲亚种（Bacillus thuringiensis subsp. tenebrionis，简称Btt）可产生一种鞘翅目特异性晶体原毒素蛋白（Cry3Aa δ-内毒素）。1982年该菌种被发现后，菌株NB125（保藏编号DSM 5526）最终于1990年获批用于防治科罗拉多马铃薯甲虫（Leptinotarsa decemlineata）。对NB125进行γ辐照诱变后，获得了高表达cry3Aa基因的衍生菌株NB176-1（保藏编号DSM 5480），该菌株随后成为植保产品诺沃多®FC（Novodor® FC）的核心活性成分。本研究对亲本菌株NB125、其衍生菌株NB176-1以及当前商业化生产菌株NB176开展了比较基因组分析。研究采用短读长（Illumina）与长读长（纳米孔）测序技术相结合的混合从头组装策略，完成了亲本及所有衍生菌株的全基因组测序与解析。基因组组装结果显示，所有供试菌株均包含一条长度为5.4~5.6 Mbp的染色体，以及6个大小介于14.9~250.5 kbp之间的质粒。亲本NB125与衍生菌株NB176-1、NB176之间的核心遗传差异包括：额外获得的cry3Aa基因拷贝易位至另一质粒，以及NB176菌株中存在一段约178 kbp的染色体缺失区域。本研究进一步通过硅基分析（in silico），对组装完成的基因组序列中的毒力与抗菌药物耐药（AMR）基因进行了全面筛查与分析。