Physiological response and molecular mechanism of glyphosate degradation by Pseudomonas alcaligenes Z1–1

The accumulation of glyphosate during its application in agriculture and its toxicity seriously threaten ecosystems and human health. Currently, glyphosate residual contamination is mainly accomplished through bioremediation techniques based on enhanced microbial degradation activity. However, there are drawbacks, such as poor environmental adaptability of strains and low degradation efficiency. Therefore, in this study, an efficient glyphosate-degrading strain, Pseudomonas alcaligenes Z1–1, was isolated from herbicide-contaminated environments and was capable of completely degrading glyphosate at a concentration of 200 mg/L within 7 days. Kinetics analysis showed that glyphosate degradation was concentration-dependent, with a maximum tolerant concentration of 800 mg/L. Mass spectrometric analysis indicated that AminoMethylPhosphonic acid (AMPA) was the predominant intermediate produced in the degradation pathway of glyphosate, revealing that glyphosate destruction began with breaking the C-N bond. Whole genome sequencing identified the key genes potentially involved in glyphosate degradation, including the thiO, glpA, aroA, soxB, and argA genes. Furthermore, in contrast to the majority of the metabolic pathways previously reported for glyphosate degradation via glyphosate oxidoreductase, the breaking of the C-N bond was primarily catalyzed by glycine oxidase. Overall, this research provides novel insights into the mechanisms of glyphosate degradation, offering valuable degradation enzyme resources for future applications.