Dynamic migration and risk of cephalosporin antibiotic resistance genes: Move from pharmaceutical plants through wastewater treatment plants to coastal tidal flats sediments.

The migration and dissemination of antibiotics and their corresponding antibiotic resistance genes (ARGs) from pharmaceutical plants through wastewater treatment to the environment introduce exogenous ARGs, increasing the risk of antibiotic resistance. Cephalosporin antibiotics (Ceps) are among the most widely used antibiotics with the largest market scale today, and the issue of resistance is becoming increasingly severe. In this study, a cephalosporin pharmaceutical plant was selected and metagenomic analysis was employed to investigate the dissemination patterns of cephalosporin antibiotics (Ceps) and their ARGs (CepARGs) from the pharmaceutical plant through the wastewater treatment plant to tidal flats sediments. The findings revealed a significant reduction in the total concentration of Ceps by 90.32 % from the pharmaceutical plant's Pioneer Bio Reactor (PBR) to the effluent of the wastewater treatment plant, and a notable surge of 172.13 % in the relative abundance of CepARGs. It was observed that CepARGs originating from the PBR could migrate along the dissemination chain, contributing to 60 % of the CepARGs composition in tidal flats sediments. Microorganisms play a crucial role in the migration of CepARGs, with efflux-mediated CepARGs, as an intrinsic resistance mechanism, exhibiting a higher prospensity for migration due to their presence in multiple hosts. While Class I risk CepARGs are present at the pharmaceutical and wastewater plant stages, Class I ina-CepARGs are completely removed during wastewater treatment and do not migrate to the environment. This study reveals the dynamic migration characteristics and potential risk changes regarding Ceps and CepARGs in real dissemination chains, providing new theoretical evidence for the mitigation, control, and risk prevention of CepARGs.

Methane-dependent complete denitrification by a single Methylomirabilis bacterium.

Methane-dependent nitrate and nitrite removal in anoxic environments is thought to rely on syntrophy between ANME-2d archaea and bacteria in the genus 'Candidatus Methylomirabilis'. Here we enriched and purified a single Methylomirabilis from paddy soil fed with nitrate and methane, which is capable of coupling methane oxidation to nitrate reduction via nitrite to dinitrogen independently. Isotope labelling showed that this bacterium we name 'Ca. Methylomirabilis sinica' stoichiometrically performed methane-dependent complete nitrate reduction to dinitrogen gas. Multi-omics analyses collectively demonstrated that 'M. sinica' actively expressed a well-established pathway for this process, especially including nitrate reductase Nap. Furthermore, 'M. sinica' exhibited a higher nitrate affinity than most denitrifiers, implying its competitive fitness under oligotrophic nitrogen-limited conditions. Our findings revise the paradigm of methane-dependent denitrification performed by two organisms, and the widespread presence of 'M. sinica' in public databases suggests that the coupling of methane oxidation and complete denitrification in single cells substantially contributes to global methane and nitrogen budgets.