Highly Selenite-Tolerant Strain QZB-2 Rapidly Reduces Selenite to Selenium Nanoparticles in the Cell Membrane.

The application of biosynthesized nano-selenium fertilizers to crops can improve their nutrient levels by increasing their selenium content. However, microorganisms with a high selenite tolerance and rapid reduction rate accompanied with the production of selenium nanoparticles (SeNPs) at the same time have seldom been reported. In this study, a bacterial strain showing high selenite resistance (up to 300 mM) was isolated from a lateritic red soil and identified as QZB-2. This strain reduced nearly 100% of 1.0 and 2.0 mM selenite within 12 and 18 h, respectively, to produce SeNPs. QZB-2 isolate reduced SeO to Se in the cell membrane with NADPH or NADH as electron donors. Se was then released outside of the cell, where it formed spherical SeNPs with an average hydrodynamic diameter of 152.0 ± 10.2 nm. QZB-2 could be used for SeNPs synthesis owing to its simultaneously high SeO tolerance and rapid reduction rate.