Selenite tolerance, reduction performance and biogenic selenium nanoparticle biosynthesis by Priestia aryabhattai YL286 isolated from the wheat phyllosphere

The phyllosphere is a promising reservoir of microbial resources and the selenite biotransformation potential of phyllosphere bacteria remains poorly characterized. In this study, a selenite-resistant bacterial strain YL286 was isolated from the wheat phyllosphere and identified as Priestia aryabhattai via 16 S rRNA gene phylogeny. We systematically evaluated its selenite tolerance, reduction kinetics, biogenic selenium nanoparticle biosynthesis, and Transcriptomic adaptation under extreme selenite stress. The strain tolerated up to 50 mM sodium selenite, with a 24 h growth lag phase followed by metabolic recovery. Under 1 mM and 2 mM selenite conditions, selenite reduction occurred predominantly during the stationary phase, achieving 90% and 60% reduction efficiency after 60 h of incubation, respectively. The biosynthesized selenium nanoparticles were spherical, with an average hydrodynamic diameter of 315.7 nm and a zeta potential of -27.9 mV. TEM and STEM-EDS analyses confirmed elemental selenium as the core component, with a surface-associated organic capping layer. Transcriptomic analysis under 50 mM selenite exposure revealed coordinated upregulation of central carbon metabolism, glutathione metabolism, and sulfur/selenium detoxification pathways, while biofilm formation and anabolic biosynthetic processes were significantly down-regulated. This transcriptional profile reflected an energy-prioritized stress adaptation strategy rather than a dedicated selenium nanoparticle biosynthesis program. To our knowledge, this study provides the first systematic characterization of selenite biotransformation and biogenic selenium nanoparticle biosynthesis in Priestia aryabhattai. The strain represents a phyllosphere-derived bacterial candidate for green selenium nanomaterial synthesis. The findings also offer preliminary information on selenite stress adaptation in phyllosphere bacteria.