目的 鉴定Bifidobacterium longum JDM301 (B.longum JDM301)染色体上的BLJ_864、BLJ_865是否构成mazEF家族的一组Ⅱ型毒素—抗毒素系统(TA系统)。方法 通过RT-PCR分析BLJ_864和BLJ_865在B.longum JDM301以及E.coli中的共转录；通过将带有BLJ_864和BLJ_865的完整操纵子的质粒转化入E. coli，证明同一操纵子中的BLJ_864、BLJ_865所编码的抗毒素蛋白和毒素蛋白共表达；通过在E.coli中单独表达BLJ_864编码的毒素蛋白或将其与BLJ_865编码的抗毒素蛋白共表达，鉴定BLJ_864编码的毒素蛋白对细菌生长的抑制作用及其对应的BLJ_865编码的抗毒素蛋白能否消除毒素蛋白的生长抑制作用。结果 BLJ_864和BLJ_865构成一个二元操纵子，两者在其天然菌株B.longum JDM301中可以共转录；异丙基-β-D 硫代半乳糖苷（IPTG）诱导下，BLJ_864和BLJ_865所编码的抗毒素蛋白和毒素蛋白在异源宿主E. coli中共表达。BLJ_864编码的毒素蛋白的表达抑制异源宿主E.coli的生长，而将BLJ_865所编码的抗毒素蛋白与BLJ_864编码的毒素蛋白共表达则可以拮抗毒素蛋白的生长抑制作用。结论 B.longum JDM301基因组中的假定基因BLJ_864和BLJ_865编码一组有功能的、隶属mazEF家族的Ⅱ型TA系统。

Objective To identify whether the BLJ_864 and BLJ_865 in the chromosome of Bifidobacterium longum JDM301 (B.longum JDM301) constitute a type II toxinantitoxin system (TA system) of mazEF family. Methods The co-transcription of BLJ_864 and BLJ_865 in B.longum JDM301 and E.coli was analyzed by the RT-PCR. The co-expression of BLJ_864 and BLJ_865 encoded antitoxin protein and toxin protein in the intact operon that carried BLJ_864 and BLJ_865 was proved by transforming the plasmid, which carried the operon, into the E.coli strain. The inhibition effect of BLJ_864 encoded toxin protein on the growth of E.coli cells and the corresponding effect of BLJ_865 encoded antitoxin protein on removing the inhibition effect were identified by the expression of BLJ_864 encoded toxin protein or co-expression of the toxin protein and BLJ_865 encoded antitoxin protein in E.coli. Results BLJ_864 and BLJ_865 constituted a dual operon and could co-transcript in the natural strain of B.longum JDM301. BLJ_864 encoded toxin protein and BLJ_865 encoded antitoxin protein could co-express in the heterologous host of E.coli when induced by isopropyl-β-D-thiogalactopyranoside (IPTG). The expression of BLJ_864 encoded toxin protein inhibited the growth of E.coli, while the co-expression of BLJ_864 encoded toxin protein and BLJ_865 encoded antitoxin protein could antagonize the inhibition effect of toxin protein. Conclusion BLJ_864 and BLJ_865 in the chromosome of B.longum JDM301 encode a functional type II TA system of mazEF family.