Synthetic Lethality of the bfr and mbfA Genes Reveals a Functional Relationship between Iron Storage and Iron Export in Managing Stress Responses in Bradyrhizobium japonicum.
Synthetic Lethality of the bfr and mbfA Genes Reveals a Functional Relationship between Iron Storage and Iron Export in Managing Stress Responses in Bradyrhizobium japonicum.
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DOI：
10.1371/journal.pone.0157250
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
O'Brian MR
中科院分区：
文献类型：
--
作者：
Sankari S;O'Brian MR
慢生型日本根瘤菌MBFA突变体铁输出缺陷，对高浓度铁或H_2O_2短期暴露敏感。在这里，我们发现生长在高铁介质(100μM)中的MBFA菌株对这些处理产生了抗药性，表明了一种应激反应适应。BfR基因编码铁储存蛋白细菌铁蛋白，其表达受铁的抑制。一株MBFA BfR双突变体在高铁培养条件下表现出严重的生长表型，表现为胁迫适应性丧失。此外，BfR被结构性去抑制的bfrup等位基因赋予MBFA突变体压力耐受性，而不会增加生长介质中的铁含量。即使在相对较低的铁培养基中(5μM)，MBFA BfR双突变株的细胞内铁含量也显著高于野生株。在此条件下，MBFA BfR株中铁反应基因的表达发生异常。此外，该双突变株对铁激活的抗生素链球菌素敏感。我们得出结论，MBFA和BfR协同工作，管理铁和氧化应激。此外，铁的解毒需要不仅限于极端环境，也是正常细胞功能所必需的。
An mbfA mutant of Bradyrhizobium japonicum defective in iron export is sensitive to short term exposure to high levels iron or H2O2. Here, we found that the mbfA strain grown in elevated iron media (100 μM) became resistant to those treatments, suggesting a stress response adaptation. The bfr gene encodes the iron storage protein bacterioferritin, and its expression is derepressed by iron. An mbfA bfr double mutant showed a loss of stress adaptation, and had a severe growth phenotype in high iron media. Moreover, a bfrup allele in which bfr is constitutively derepressed conferred stress tolerance on an mbfA mutant without elevating the iron content in the growth media. The intracellular iron content of the mbfA bfr double mutant was substantially higher than that found in the wild type, even when grown in relatively low iron media (5 μM). Under that condition, iron-responsive gene expression was aberrant in the mbfA bfr strain. Moreover, the double mutant was sensitive to the iron-activated antibiotic streptonigrin. We conclude that MbfA and Bfr work in concert to manage iron and oxidative stresses. In addition, the need for iron detoxification is not limited to extreme environments, but is also required for normal cellular function.