Abstract
PURPOSE: Biogenic selenium nanoparticles (SeNPs) offer an eco-friendly alternative to chemical synthesis for producing bioavailable and stable selenium. This study aimed to isolate an efficient Se(IV)-reducing bacterium from livestock manure and to elucidate the molecular mechanisms underlying SeNP biosynthesis, providing insight into its potential agricultural applications. METHODS: A selenium-transforming strain was isolated from goat manure and identified as Lactiplantibacillus plantarum SMB14 based on 16 S rRNA sequencing. The strain was cultured in MRS broth supplemented with sodium selenite (Na(2)SeO(3): 100 mg L⁻¹) to produce SeNPs, which were characterized. Transcriptomic sequencing was conducted to compare gene expression profiles between control and Se(IV)-treated cells, and functional enrichment analyses were performed to identify metabolic pathways involved in Se(IV) reduction. RESULTS: SMB14 exhibited high Se(IV)-reducing efficiency (> 80%) and produced extracellular SeNPs stabilized by biomolecular coatings. Transcriptome analysis revealed 978 differentially expressed genes, with significant upregulation of redox-active oxidoreductases (qorB, SDR family), thiol-related enzymes (TrxA, GorA), and membrane transporters (pstS, glpF2, nhaC). Functional pathways related to oxidative phosphorylation, amino acid metabolism, and cellular redox balance were significantly enriched, supporting a coordinated enzymatic–nonenzymatic reduction mechanism. CONCLUSION: This study demonstrates that L. plantarum SMB14 employs a multi-pathway redox network to convert toxic Se(IV) into stable SeNPs through synergistic enzymatic and thiol-mediated reductions. These findings highlight the potential of SMB14 as a green biocatalyst for nanoselenium production and as a probiotic platform for sustainable selenium supplementation in agriculture and environmental biotechnology. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s42770-026-01901-3.