Uptake of Selenite by Rahnella aquatilis HX2 Involves the Aquaporin AqpZ and Na + /H + Antiporter NhaA.

Microbial transformation of selenite [Se(IV)] to elemental selenium nanoparticles (SeNPs) is known to be an important process for removing toxic soluble selenium (Se) oxyanions and recovery of Se from the environment as valuable nanoparticles. However, the mechanism of selenite uptake by microorganisms, the first step through which Se exerts its cellular function, remains not well studied. In this study, the effects of selenite concentration, time, pH, metabolic inhibitors, and anionic analogues on selenite uptake in HX2 were investigated. Selenite uptake by . HX2 was concentration- and time-dependent, and its transport activity was significantly dependent on pH. In addition, selenite uptake in . HX2 was significantly inhibited by the aquaporin inhibitor AgNO and sulfite (SO), and partially inhibited by carbonyl cyanide -chlorophenyl hydrazone (CCCP) and 2,4-dinitrophenol (2,4-DNP) treatments. Three mutants with in-frame deletions of Z, F, and A genes were constructed. The transport assay showed that the water channel protein AqpZ, and not GlpF, was a key channel of selenite uptake by . HX2, and sulfite and selenite had a common uptake pathway. In addition, the Na/H antiporter NhaA is also involved in selenite uptake in . HX2.