Molecular Response Mechanism of Pseudomonas Nicosulfuronedens LAM1902 to A Typical Sulfonylurea Herbicide Nicosulfuron

The overuse of the herbicide nicosulfuron (NS) has become a global environmental concern. As a potential bioremediation technology, the microbial degradation of NS shows much promise; however, the detailed mechanisms of microbial taxa responding to NS exposure require further study. An isolated soil-borne bacteria Pseudomonas nicosulfuronedens LAM1902 displaying NS degradabilities was used to characterize the molecular responses to NS exposure, and LAM1902 can degrade exceed 95% of 50 mg/L nicosulfuron under the optimal conditions. Using transcriptomic sequencing, RNA-Seq results indicated that 1102 differentially expressed genes (DEGs) were up-regulated and 702 down-regulated in response to NS. Among them, “ABC transporters,” “sulfur metabolism,” and “ribosome” gene pathways were significantly enriched ( p  ≤ 0.05). Several gene pathways involved in the glycolysis and pentose phosphate pathways, a two-component regulation system, as well as in bacterial chemotaxis metabolisms were up-regulated under NS exposure. Surprisingly, NS exposure showed positive effects on the production of oxalic acid that is synthesized by genes encoding glycolate oxidase through the glyoxylate cycle pathway. The results suggest that P. nicosulfuronedens LAM1902 adopt acid metabolites production strategies in response to NS, with concomitant NS degradation. Meanwhile, strain LAM1902 likely grows and survives amid NS stress by increased energy production. The present studies provide a glimpse at the molecular response of microorganisms to sulfonylurea pesticide toxicity and a potential framework for future mechanistic studies.