A novel strain (Acinetobacter junii) demonstrating high-level resistance to sulfamethoxazole: comprehensive...

Sulfamethoxazole (SMX) is a commonly detected antibiotic in municipal wastewater and has been reported to adversely affect biological nutrient removal processes. This study aimed to systematically investigate the physiological performance and adaptive mechanisms of Acinetobacter junii (BWFJF1), a denitrifying polyphosphate-accumulating organism (DPAO), in response to increasing SMX stress.

Strain BWFJF1 was exposed to SMX concentrations ranging from 0.0 to 10.0 mg L⁻¹ to evaluate nitrogen and phosphorus removal performance and stress responses. The strain maintained stable nitrogen removal across all treatments and exhibited a marked enhancement of phosphorus removal at high SMX concentrations, challenging the conventional expectation that the metabolic cost of antibiotic resistance impairs nutrient removal. SEM-EDS analysis revealed pronounced morphological changes accompanied by increased phosphorus accumulation on the cell surface. Transcriptomic analysis showed significant upregulation of genes associated with efflux systems, phosphate transport, and energy metabolism, while metabolomic profiling indicated extensive metabolic reprogramming involving the TCA cycle, amino acid biosynthesis, and lipid remodeling.

These findings demonstrate that Strain BWFJF1 employs an SMX-induced adaptive strategy that couples antibiotic resistance with reinforced phosphorus metabolism, thereby sustaining efficient nutrient removal under antibiotic stress.