Abstract:In recent years，microbial transformation technology has become an important means to improve the bioavailability of selenium in soil，especially by converting low-potency selenite into selenium nanoparticles（SeNPs）with higher biological activity. In this study，a high selenium-tolerant strain NL4 was isolated and identified from the rhizosphere soil of Cardamine violifolia.Its growth characteristics，biological traits，and selenium reduction capability were investigated，and the product SeNPs were systematically characterized. By detecting the transcriptional level changes of global transcriptional regulators，namely CcpA and CodY，the response of the carbon and nitrogen metabolism regulatory network to sodium selenite was analyzed. The results showed that strain NL4 was identified as Bacillus sonorensis. It was sensitive to multiple antibiotics and exhibited the ability to produce protease and amylase. Growth characteristics of the strain were evaluated under different temperatures，pH values，and NaCl concentrations，and it was found that the strain grew well at 35 ℃，pH6.0，and with 1% NaCl. Under these optimal conditions，it reduced 85.94% of 2.5 mmol/L sodium selenite within 24 hours and produced spherical nanoparticles. Sodium selenite treatment increased the expression level of the global transcriptional regulator CcpA gene while decreasing that of the CodY gene，resulting in inhibited carbon metabolism and enhanced nitrogen metabolism in the strain.Based on the product characterization results，the synthesized spherical nanoparticles were confirmed to be SeNPs，which were coated with proteins and polysaccharides and exhibited a small particle size and good stability.