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A typeⅡ toxin-antitoxin system encoded by BLJ_864 and BLJ_865 in chromosome of Bifidobacterium longum

WEI Yan-xia1,2, YE Lu2, LIU Dian-bin3, GUO Xiao-kui2   

  1. 1.Department of Pathogenic Biology and Immunology, Xuzhou Medical College, Xuzhou 221004, China; 2.Department of Microbiology and Immunity, Basic Medicine Faculty, Shanghai Jiao Tong University, Shanghai 200025, China; 3.School of Stomatology, Xuzhou Medical College, Xuzhou 221004, China
  • Online:2014-09-28 Published:2014-09-26
  • Supported by:

    National Natural Science Foundation of China, 31300029;Natural Science Foundation of Jiangsu Province, China, BK20130213; Qing Lan Project for Excellent Young Teachers in Higher Education of Jiangsu; Scientific Research Foundation for Talents of Xuzhou Medical College, D2012014

Abstract:

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.

Key words: toxin-antitoxin system, Bifidobacterium longum, mazEF