Biotransformation of the herbicide nicosulfuron residues in soil and seven sulfonylurea herbicides by Bacillus subtilis YB1: A climate chamber study

Bacillus subtilis YB1 is a strain that can efficiently transform nicosulfuron. In order to study its remediation ability and effects on other microorganisms in the soil, indoor biological remediation experiments and rhizosphere microbial diversity analysis were performed. B. subtilis YB1 granules were prepared and applied to the nicosulfuron contaminated soil. The concentration of nicosulfuron was detected by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and changes in the physiological indicators of wheat were measured. At the same time, the changes in the rhizosphere soil microbial diversity were determined by 16S RNA sequencing. Results showed that the YB1 granules made a contribution to the transformation of nicosulfuron (0.05 mg kg⁻¹) in the soil within 55 days. The physiological indicators of wheat also showed consistent result about nicosulfuron transformation. Rhizosphere soil microbial diversity results indicated the relative abundance of Firmicutes decreased (3.0%–0.35%) and Acidobacteria first decreased (25.82%–22.38%) and then increased (22.3%–26.1%) with nicosulfuron added (N group). The relative abundance of Acidobacteria first decreased (25.8%–15.3%) and then increased (15.3%–21.7%) while Proteobacteria increased (26.5%–38.08%). At the same time, Firmicutes first increased (2.6%–12.3%) and then decreased to original level (12.3%–0.7%) in the N group with YB1 granules (NYB1 group). Members of the genus Bacillus initially increased and then decreased to the original level as the Control group, therefore, they did not become dominant in the rhizosphere soil. Alpha diversity analyses showed no obvious differences in species diversity among the N, NYB1 and Control groups. So YB1 did not have obvious influence on the rhizosphere microbial community structure during nicosulfuron transformation, which only had some effect on species abundance. This study revealed the successful indoor bioremediation of nicosulfuron in the soil, providing a potential strategy for solving the problem of nicosulfuron contamination.