Iron Incorporation in Rhodochrosite Boosts Encapsulation of Environmental Antibiotic Resistance Genes

The environmental dissemination of extracellular antibiotic resistance genes (eARGs) has raised significant public health concerns. While rhodochrosite, a mineral commonly found in anaerobic environments, forms manganese oxide (MnO x ) films upon exposure to oxygen, little is known about its role in the fate and transport of pollutants, including eARGs. This study explored how the incorporation of iron (Fe) into the rhodochrosite crystal lattice influenced its reactivity and subsequent interactions with eARGs. To this end, we systematically tuned the Fe content in rhodochrosite and compared its effect on eARG encapsulation to that of Fe-free rhodochrosite. At a Fe:Mn molar ratio of 20:80 (RCF20), the MnO x film exhibited a growth rate constant of 0.09 h-1, approximately 265 times greater than that of the Fe-free rhodochrosite. Atomic force microscopy (AFM) provided in situ observation of eARGs undergoing anaerobic adsorption and aerobic encapsulation within the MnO x film. Desorption experiments confirmed the stable encapsulation of the eARGs. The incorporation of Fe into rhodochrosite enhanced the eARG encapsulation efficiency, a finding validated with three different environmental water samples. The accelerated growth of MnO x films in Fe-incorporated rhodochrosite was attributed to a reduced bandgap, facilitating faster electron transfer during oxidation. These results introduce a novel mechanism for the stabilization of eARGs in the environment through adsorption and encapsulation within oxidized mineral films. Importantly, Fe incorporation significantly enhanced this process, offering new insights into natural self-purification mechanisms for mitigating antibiotic resistance and providing a potential strategy for controlling eARG dissemination.