Impact of glyphosate on soil bacterial communities and degradation mechanisms in large-leaf tea plantations

This study investigated the impact of glyphosate on bacterial communities and their degradation mechanisms in large-leaf tea soil, through exposure microcosm and enrichment culture experiments. Soils from three tea gardens in Yunnan, China, were used: two glyphosate-free (JM and KL) for microcosm study and one long-term exposed (G2) for enrichment culture experiment. The results revealed a two-phase degradation process with half-lives of 12.7 to 268 days, while the metabolite AMPA was notably persistent. The acidic conditions and high organic content of tea soils may retard glyphosate microbial availability and degradation. Glyphosate initially stimulated bacterial growth but led to abundance declines with prolonged exposure. It tended to enhance bacterial diversity at lower doses. Network complexity increased in JM soil where strong adsorption moderated glyphosate exposure, yet decreased in KL soil where weak adsorption enabled greater microbial-glyphosate interactions. Community structure analysis revealed soil-specific responses, with decreased Proteobacteria in JM soil and Actinobacteria in KL soil, while several phyla including Proteobacteria, Acidobacteriota, Chloroflexi, Myxococcota, and Verrucomicrobiota showed increased abundance. PICRUSt2 analysis indicated enhanced biosynthesis and cell growth pathways, while carbohydrate metabolism, nitrogen metabolism, and xenobiotics biodegradation pathways were reduced. LEfSe analysis identified potential degrading biomarkers primarily from Proteobacteria, Acidobacteriota, Myxococcota, Chloroflexi, and Actinobacteriota, suggesting their putative role in degradation. The enriched consortium G2 efficiently degraded 400 mg/L glyphosate within 7 days, with notable increases in Afipia, Dokdonella, and Cohnella abundance. This study provides insights into bacterial interactions with glyphosate in tea soils, suggesting strategies for contamination mitigation and environmental restoration.