Organic Matter Micro-Interfaces Change Glyphosate Partitioning and Alter Active Glyphosate Degraders in Soils

Soil microorganisms are responsible for natural glyphosate dissipation. However, previous studies have largely focused on bulk soils, and the underlying microscale mechanisms remain poorly resolved. In this study, we investigated the physicochemical properties and glyphosate adsorption on two representative soil microinterfaces of particulate organic matter (POM) and mineral-associated organic matter (MAOM) and explored the change in the active glyphosate degraders using DNA stable-isotope-probing (DNA-SIP). Owing to the rough, open structure and accessible functional groups, POM displayed a higher glyphosate adsorption capability (9.41 mg/kg) than MAOM (6.75 mg/kg). Soil microorganisms significantly enhanced the conversion of glyphosate to aminomethylphosphonic acid. The active glyphosate degraders were Streptomyces, Clostridium, and Lysobacter in bulk soils, Streptomyces, Clostridium, Steroidobacter, Herbaspirillum, Lysobacter, and Opitutus on POM, and Streptomyces on MAOM, as revealed by DNA-SIP. POM harbored the highest diversity and abundance of the putative glyphosate degraders, behaving as the principal micro-interface coupling glyphosate retention and biodegradation. Our findings revealed distinct patterns of glyphosate retention and distributions of putative glyphosate degraders at POM and MAOM micro-interfaces, providing an interface-scale perspective on glyphosate fate in soil.