Degradation of sulfonamide antibiotics in the rhizosphere of two dominant plants in Huixian karst wetland, Guangxi, China

Abstract

In this work, Phragmites australis and Vallisneria natans were selected as the research objects and were cultured for 10 d under 0.10 μg L−1 sulfadiazine (SD) stress in a simulated surface flow wetland reactor. SD degradation was conducted at pH = 7 and 25 °C for 96 h. Each plant group conformed to the first-order kinetic model of degradation, and the degradation rate increased with time, reaching the maximum at 96 h. At 96 h, the degradation rate of P. australis communities was higher than that of V. natans. SD metabolites showed that the degradation pathways in the plant rhizosphere were mainly hydroxylation, aminolation, and S–N bond cleavage. In the analysis of rhizosphere bacterial community structure, the bacterial phyla that could degrade antibiotics accounted for a large proportion. Compared with before degradation, the dominant phylum and genus did not change after degradation (96 h), but their abundance changed to varying degrees, and new genera appeared in the P. australis group. This research provides a reference for the degradation of antibiotics in karst areas and new information on the mechanism of SA degradation in the plant rhizosphere. HIGHLIGHTS Under sulfonamide (SD) stress, the contents of organic acid esters in rhizosphere exudates of P. australis and V. natans increased.; New genera were produced in rhizosphere soil of P. australis group during SD degradation.; Antibiotics in karst wetlands may exist in the form of complexes and be adsorbed in soil or sediments.; After SD degradation, the diversity of bacteria decreased, but the total number of bacteria increased.;

Keywords

• bacterial community
• degradation
• karst wetland
• rhizosphere secretion
• sulfonamides antibiotics