Anaerobic Transformation and Detoxification of Sulfamethoxazole by Sulfate-Reducing Enrichments and Desulfovibrio vulgaris

Abstract

Sulfamethoxazole (SMX) is a veterinary antibiotic that is not efficiently removed from wastewater by routine treatment and therefore can be detected widely in the environment. Here, we investigated whether microbial anaerobic transformation can contribute to the removal of SMX in constructed systems. We enriched SMX-transforming mixed cultures from sediment of a constructed wetland and from digester sludge of a wastewater treatment plant. Transformation of SMX was observed in both sulfate-reducing and methanogenic cultures, whereas nitrate-reducing cultures showed no SMX transformation. In sulfate-reducing cultures, up to 90% of an initial SMX concentration of 100–250 μM was removed within 6 weeks of incubation, and the experiments demonstrated that the transformation was microbially catalyzed. The transformation products in sulfate-reducing cultures were identified as the reduced and isomerized forms of the isoxazole SMX moiety. The transformation products did not spontaneously reoxidize to SMX after oxygen exposure, and their antibacterial activity was significantly decreased compared to SMX. Population analyses in sequential transfers of the sulfate-reducing cultures revealed a community shift toward the genus Desulfovibrio. We therefore tested a deposited strain of Desulfovibrio vulgaris Hildenborough for its capacity to transform SMX and observed the same transformation products and similar transformation rates as in the enrichment cultures. Our work suggests that an initial anaerobic step in wastewater treatment can reduce the concentration of SMX in effluents and could contribute to decreased SMX concentrations in the environment.

Highly Efficient Reductive Detoxification of Sulfamethoxazole by Palladium Nanoparticles Deposited on H2-Transfer Membranes

“…In addition, the m / z values of fragment ions of this TP were 92, 108 and 156 (Figure D). It is worth noting that the m / z 156 ion belongs to the aniline moiety with a sulfo group that was generated by cleaving the sulfonamide bond . By comparing the predicted chemical structure of this TP and SMX, we proposed the mechanism of hydrogen drive catalytic reduction of SMX: H 2 cleaves the N–O bond via a nucleophilic attack to generate an opened ring, while the O–H bond in the ring captures the electron pair.…”

“…The E. coli was inoculated into the medium with 3% (v/v) overnight on a rotary shaker (37 °C, 200 rpm). Liquid samples were collected at 0, 2, 4, and 7 h, and the growth of E. coli was detected using a spectrophotometer at the wavelength 600 nm (OD 600 ). − Each test was performed in triplicate.…”

A Review on Microorganisms in Constructed Wetlands for Typical Pollutant Removal: Species, Function, and Diversity

“…Sulfonamides (SAs), including sulfamethoxazole (SMX) and sulfadiazine (SDZ), are widely used in animal agriculture and human health care and are the most common residual antibiotics in almost all environmental compartments ( Ouyang et al, 2021 ). They can significantly inhibit bacterial populations, such as Desulfarculus , denitrifying bacteria, and Syntrophobacter , affecting the sulfur and nitrogen cycles ( Man et al, 2020 ).…”

“…Geobacter , a member of the phylum Proteobacteria , is considered a potential SDZ degrader ( Zhang et al, 2019a ). The genus Microbacterium in the phylum Actinobacteria can also use SMX as the sole carbon source under aerobic conditions ( Sauvetre et al, 2020 ; Ouyang et al, 2021 ). The molecular mechanism of SMX catabolism by Microbacterium is initiated by ipso-hydroxylation, followed by NADH-dependent hydroxylation of the carbon atom attached to the sulfonyl group, which leads to the release of sulfite, 3-amino-5-methylisoxazole, and benzoquinone imine, of which the latter is converted to 4-aminophenol ( Ricken et al, 2013 ).…”

“…In CWs, the three main phyla involved in the degradation of SAs are Proteobacteria , Actinobacteria and Firmicutes , and some key genera, such as Pseudomonas , may metabolize glucose and subsequently attenuate SMX by co-metabolism of organic matter and SMX ( Zheng et al, 2021b ). In addition, Desulfovibrio also plays a key role in SMX transformation and can transform SMX alone ( Ouyang et al, 2021 ).…”