Activation of the chromosomally encoded mazEF(Bif) locus of Bifidobacterium longum under acid stress.
Activation of the chromosomally encoded mazEF(Bif) locus of Bifidobacterium longum under acid stress.
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DOI：
10.1016/j.ijfoodmicro.2015.04.028
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发表时间：
2015-08
影响因子：
5.4
通讯作者：
Yan-xia Wei;L. Ye;Dianbin Liu;Zhuo-Yang Zhang;Chang Liu;Xiao-kui Guo
中科院分区：
文献类型：
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作者：
Yan-xia Wei;L. Ye;Dianbin Liu;Zhuo-Yang Zhang;Chang Liu;Xiao-kui Guo
毒素-抗毒素（TA）系统分布在几乎所有自由生活的细菌的基因组中。虽然染色体编码的TA系统的作用仍在争论中，他们被怀疑参与各种应激反应。在这里，我们提供了第一份报告的II型TA系统中的益生菌长双歧杆菌。B.的生物信息学分析longumJDM 301基因组鉴定了在基因座BLJ_811-BLJ_812处编码MazEF样TA系统的一对连锁基因。结果表明，B. longum mazEFB基因形成双顺反子操纵子。过量表达MazFBif对大肠杆菌具有毒性，并可被其同源抗毒素MazEBif的共表达所中和。我们证明MazEFBif在酸应激期间被激活，这最有可能在胃肠道中遇到。此外，我们发现，蛋白酶ClpPXBif，除了MazEFBif，在酸胁迫下诱导。此外，我们检查了MazEFBif随时间的抗毒素水平，并观察到抗毒素MazEFBif被ClpPXBif降解，这表明MazEFBif通过ClpP 1XBif和ClpP 2XBifunder酸胁迫水解MazEFBif而被激活。我们的研究结果表明，MazEFBifTA模块可能在细胞生理学中发挥重要作用，并可能代表细胞生长调节剂，帮助细菌科普胃肠道和环境中的酸应激。
Toxin–antitoxin (TA) systems are distributed within the genomes of almost all free-living bacteria. Although the roles of chromosomally encoded TA systems are still under debate, they are suspected to be involved in various stress responses. Here, we provide the first report of a type II TA system in the probiotic bacterium Bifidobacterium longum. Bioinformatic analysis of theB. longumJDM301 genome identified a pair of linked genes encoding a MazEF-like TA system at the locus BLJ_811–BLJ_812. Our results showed thatB. longum mazEFBifgenes form a bicistronic operon. The over-expression of MazFBifwas toxic toEscherichia coliand could be neutralized by the co-expression of its cognate antitoxin MazEBif. We demonstrated that MazEFBifwas activated during acid stress, which would most likely be encountered in the gastrointestinal tract. In addition, we found that the protease ClpPXBif, in addition to MazEFBif, was induced under acid stress. Furthermore, we examined antitoxin levels over time for MazEFBifand observed that the antitoxin MazEBifwas degraded by ClpPXBif, which suggested that MazEFBifwas activated through the hydrolysis of MazEBifby ClpP1XBifand ClpP2XBifunder acid stress. Our results suggest that the MazEFBifTA module may play an important role in cell physiology and may represent a cell growth modulator that helps bacteria to cope with acid stress in the gastrointestinal tract and environment.