Regulation of arsenite oxidation by the phosphate two-component system PhoBR in Halomonas sp. HAL1.
Regulation of arsenite oxidation by the phosphate two-component system PhoBR in Halomonas sp. HAL1.
复制标题
盐单胞菌中磷酸双组分系统 PhoBR 对亚砷酸盐氧化的调节。
DOI：
10.3389/fmicb.2015.00923
复制
发表时间：
2015
影响因子：
5.2
通讯作者：
Wang G
中科院分区：
文献类型：
--
作者：
Chen F;Cao Y;Wei S;Li Y;Li X;Wang Q;Wang G
以前，亚砷酸盐[As（III）]氧化酶基因aioBA的表达被报道由三个组件的调节系统，AioXSR，在一些As（III）氧化细菌菌株的调节。然而，调控机制仍然是未知的，当aioXSR基因在一些砷（III）氧化细菌基因组中，如盐单胞菌属HAL 1。本研究通过转座子诱变和基因敲除突变，从菌株HAL 1中获得了两个突变株HAL 1-phoR 931和HAL 1-phoB。phoR和phoB构成了一个双组分系统，负责磷酸盐（Pi）的获取和同化。这两个突变体显示负As（III）-氧化表型在低Pi条件下（0.1 mM），但不是在正常的Pi条件下（1 mM）。phoBR互补菌株HAL 1-phoB-C将突变体的无效表型逆转回野生型状态。同时，使用pCM-lacZ的lacZ报告基因融合显示phoBR和aioBA的表达都被As（III）诱导，但在HAL 1-phoR 931和HAL 1-phoB中不被诱导。使用15个共有的Pho盒序列，在aioBA调节区中发现推定的Pho盒。PhoB能够结合到推定的Pho框在体内（细菌单杂交检测）和体外（电泳迁移率凝胶位移测定），和一个18 bp的结合序列，含有9个保守的碱基进行了测定。本研究为PhoBR在低磷条件下调控盐单胞菌HAL 1中aioBA的表达提供了证据。新的调控模型进一步暗示了As和Pi之间的密切代谢联系。
Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR931 and HAL1-▵phoB, were obtained in strain HAL1. The phoR and phoB constitute a two-component system which is responsible for phosphate (Pi) acquisition and assimilation. Both of the mutants showed negative As(III)-oxidation phenotypes in low Pi condition (0.1 mM) but not under normal Pi condition (1 mM). The phoBR complementation strain HAL1-▵phoB-C reversed the mutants' null phenotypes back to wild type status. Meanwhile, lacZ reporter fusions using pCM-lacZ showed that the expression of phoBR and aioBA were both induced by As(III) but were not induced in HAL1-phoR931 and HAL1-▵phoB. Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region. PhoB was able to bind to the putative Pho box in vivo (bacterial one-hybrid detection) and in vitro (electrophoretic mobility gel shift assay), and an 18-bp binding sequence containing nine conserved bases were determined. This study provided the evidence that PhoBR regulates the expression of aioBA in Halomonas sp. HAL1 under low Pi condition. The new regulation model further implies the close metabolic connection between As and Pi.