Sun Meng, Lyu Mengya, Wen Ying, Song Yuan, Li Jilun, Chen Zhi
State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological Sciences, China Agricultural University, Beijing, China.
Front Microbiol. 2018 Jun 29;9:1398. doi: 10.3389/fmicb.2018.01398. eCollection 2018.
The bacterium is an industrial-scale producer of avermectins, which are important anthelmintic agents widely used in agriculture, veterinary medicine, and human medicine. During the avermectin fermentation process, is exposed to organic peroxides generated by aerobic respiration. We investigated the role of MarR-family transcriptional regulator OhrR in oxidative stress response and avermectin production in . The genome encodes two organic hydroperoxide resistance proteins: OhrB1 and OhrB2. OhrB2 is the major resistance protein in organic peroxide stress responses. In the absence of organic peroxide, the reduced form of OhrR represses the expression of gene by binding to the OhrR box in the promoter region. In the presence of organic peroxide, the oxidized form of OhrR dissociates from the OhrR box and the expression of is increased by derepression. OhrR also acts as a repressor to regulate its own expression. An -deletion mutant (termed DohrR) displayed enhanced avermectin production. Our findings demonstrate that OhrR in represses avermectin production by regulating the expression of pathway-specific regulatory gene . OhrR also plays a regulatory role in glycolysis and the pentose phosphate (PP) pathway by negatively controlling the expression of and /----.
该细菌是阿维菌素的工业规模生产者，阿维菌素是广泛应用于农业、兽医学和人类医学的重要驱虫剂。在阿维菌素发酵过程中，该细菌会接触到有氧呼吸产生的有机过氧化物。我们研究了MarR家族转录调节因子OhrR在该细菌氧化应激反应和阿维菌素生产中的作用。该细菌基因组编码两种有机氢过氧化物抗性蛋白：OhrB1和OhrB2。OhrB2是有机过氧化物应激反应中的主要抗性蛋白。在没有有机过氧化物的情况下，还原形式的OhrR通过与启动子区域的OhrR框结合来抑制基因的表达。在存在有机过氧化物的情况下，氧化形式的OhrR从OhrR框解离，基因的表达通过去阻遏而增加。OhrR还作为阻遏物来调节其自身的表达。一个OhrR缺失突变体（称为DohrR）显示出阿维菌素产量增加。我们的研究结果表明，该细菌中的OhrR通过调节途径特异性调节基因的表达来抑制阿维菌素的生产。OhrR还通过负调控和/----的表达在糖酵解和磷酸戊糖（PP）途径中发挥调节作用。
