Elucidation of new sulfamethoxazole catabolic pathways in whole-cell catalyst of bacterium Kocuria rhizophila SA117

Sulfamethoxazole (SMX) and its residues exhibit high environmental persistence due to their resistance to conventional degradation processes. The bacterial strain Kocuria rhizophila SA117, isolated from polluted soils, was characterized biochemically, phylogenetically, and -omically. Herein, we describe a complete degradation pathway for SMX and determine two putative pathways: cleavage of the benzene ring and the degradation of the substituted isoxazole, leading to the formation of non-toxic Krebs cycle metabolites. Based on molecular structures containing ¹³C₆-labeled carbons and ²H₃ atoms, thirty metabolites were identified by high-resolution tandem mass spectrometry. Genomic and proteomic analysis of strain SA117 revealed its ability to perform a wide range of metabolic activities under sulfamethoxazole selective pressure. These activities include energy and sulfur metabolism, adaptation to stress conditions, and catabolism of aromatic compounds. This study has greatly enhanced the understanding of microbial sulfonamide degradation and highlighted the potential of the bacterium Kocuria in remediation strategies.