Stable isotopes and nanoSIMS single-cell imaging reveals soil plastisphere colonizers able to assimilate sulfamethoxazole

Abstract

The presence and accumulation of both plastics and antibiotics in soils may lead to the colonization, selection and propagation of bacteria with certain metabolic traits e.g. antibiotic resistance, in plastisphere. However, the impact of plastic-antibiotic tandem on the soil ecosystem functioning, particularly on microbial function and metabolism remains currently unexplored. Herein, we investigated the competence of soil bacteria to colonize plastics and to mineralize/degrade 13C-labelled sulfamethoxazole (SMX). Using single cell imaging, isotope tracers, soil respiration and SMX mineralization bulk measurements we show that microbial colonization of polystyrene (PE) and polyethylene (PS) surfaces takes place within the first 30 days of incubation. Morphologically diverse, microorganisms were colonizing both plastic types, with a preference for PE substrate. Nano-scale Secondary Ion Mass Spectrometry measurements show that 13C enrichment was highest at 130 days with values up to 1.29 atom%, similar to those of the 13CO2 pool (up to 1.26 atom%). Our results provide direct evidence demonstrating, at single cell level, the capacity of bacterial colonizers of plastics to assimilate 13C from 13C-SMX. These findings expand our knowledge on the role of plastisphere microbiota in the ecological functioning of soils impacted by anthropogenic stressors.