Phosphate starvation response controls genes required to synthesize the phosphate analog arsenate

Environmental arsenic poisoning affects roughly 200 million people worldwide. The toxicity and mobility of arsenic in the environment is significantly influenced by microbial redox reactions, with arsenite (Asᴵᴵᴵ) being more toxic than arsenate (Asⱽ). Microbial oxidation of Asᴵᴵᴵ to Asⱽ is known to be regulated by the AioXSR signal transduction system and viewed to function for detoxification or energy generation. Here, we show that Asᴵᴵᴵ oxidation is ultimately regulated by the phosphate starvation response (PSR), requiring the sensor kinase PhoR for expression of the Asᴵᴵᴵ oxidase structural genes aioBA. The PhoRB and AioSR signal transduction systems are capable of transphosphorylation cross‐talk, closely integrating Asᴵᴵᴵ oxidation with the PSR. Further, under PSR conditions, Asⱽ significantly extends bacterial growth and accumulates in the lipid fraction to the apparent exclusion of phosphorus. This could spare phosphorus for nucleic acid synthesis or triphosphate metabolism wherein unstable arsenic esters are not tolerated, thereby enhancing cell survival potential. We conclude that Asᴵᴵᴵ oxidation is logically part of the bacterial PSR, enabling the synthesis of the phosphate analog Asⱽ to replace phosphorus in specific biomolecules or to synthesize other molecules capable of a similar function, although not for total replacement of cellular phosphate.