Response mechanisms of denitrifying anaerobic methane oxidation (DAMO) processes to typical quinolone antibiotics in freshwater wetland sub-surface sediments.

Sub-surface sediments in freshwater wetlands function as active habitats for microbial denitrifying anaerobic methane oxidation (DAMO) processes and as hotspots for antibiotic accumulation. Focusing on the Baiyangdian wetland, which is contaminated with quinolone antibiotics (QNs) and hosts active DAMO processes, this study employed ¹³C-labeled microcosm incubation experiments, RT-qPCR, and gene sequencing to decipher the response mechanisms of DAMO processes to prevalent QNs in the sub-surface sediments (0.5 20 cm) of study area. Short-term exposure (24 h) to typical QNs at 200 ng·g^-1 reduced nitrite-DAMO activities by approximately 33 %, primarily through selective inhibition of antibiotic-sensitive species within NC10 bacteria. In contrast, exposure to the same concentration of QNs enhanced nitrate-DAMO activities by about 450 %, likely due to hormetic stimulation of antibiotic-resistant ANME-2d archaea, combined with the inhibition of substrate competitor. Long-term exposure (90 days) to typical QNs mitigated these effects as bacterial adaptation to antibiotics occurred, resulting in a time-dependent attenuation of their impacts. This study underscores the significance of DAMO processes as methane sinks in changing environments and broadens the understanding of the ecological risks posed by antibiotics.