Aix-Marseille Université, CNRS, LCB UMR7283, 13009, Marseille, France.
Extremophiles. 2013 Nov;17(6):911-20. doi: 10.1007/s00792-013-0573-1. Epub 2013 Aug 24.
Thiomonas arsenitoxydans is an acidophilic and facultatively autotrophic bacterium that can grow by oxidizing arsenite to arsenate. A comparative genomic analysis showed that the T. arsenitoxydans aioBA cluster encoding the two subunits of arsenite oxidase is distinct from the other clusters, with two specific genes encoding a cytochrome c and a metalloregulator belonging to the ArsR/SmtB family. These genes are cotranscribed with aioBA, suggesting that these cytochromes c are involved in arsenite oxidation and that this operon is controlled by the metalloregulator. The growth of T. arsenitoxydans in the presence of thiosulfate and arsenite, or arsenate, is biphasic. Real-time PCR experiments showed that the operon is transcribed during the second growth phase in the presence of arsenite or arsenate, whereas antimonite had no effect. These results suggest that the expression of the aioBA operon of T. arsenitoxydans is regulated by the electron donor present in the medium, i.e., is induced in the presence of arsenic but is repressed by more energetic substrates. Our data indicate that the genetic organization and regulation of the aioBA operon of T. arsenitoxydans differ from those of the other arsenite oxidizers.
砷酸氧化硫杆菌是一种嗜酸兼性自养细菌，能够通过将亚砷酸盐氧化为砷酸盐来生长。比较基因组分析表明，T. arsenitoxydans 编码亚砷酸盐氧化酶两个亚基的 aioBA 簇与其他簇不同，有两个特定的基因编码细胞色素 c 和属于 ArsR/SmtB 家族的金属调节剂。这些基因与 aioBA 共转录，表明这些细胞色素 c 参与亚砷酸盐氧化，并且该操纵子受金属调节剂的控制。T. arsenitoxydans 在硫代硫酸盐和亚砷酸盐或砷酸盐存在下的生长呈两相性。实时 PCR 实验表明，在存在亚砷酸盐或砷酸盐的情况下，操纵子在第二生长阶段转录，而锑酸盐没有影响。这些结果表明，T. arsenitoxydans 的 aioBA 操纵子的表达受培养基中电子供体的调节，即在存在砷的情况下被诱导，但被更具能量的底物抑制。我们的数据表明，T. arsenitoxydans 的 aioBA 操纵子的遗传组织和调控与其他亚砷酸盐氧化剂不同。
