Halogenation and Dehalogenation Potential of Microorganisms in Yangtze River Waters.

The discharge of pollutants into rivers has been increasing with the rapid industrial development and extensive agricultural use of pesticides and herbicides. Halogenated organic compounds (HOCs) represent a significant class of environmental pollutants. It has been found that microorganisms have the ability not only to degrade HOCs but also to synthesize them. Little is known about the halogenation and dehalogenation potential of microorganisms in river waters. In this study, we investigated the halogenation and dehalogenation potentials of microorganisms in the Yangtze River, which originates from the Tibetan Plateau, flows through southwestern, central and eastern China, and finally joins the East China Sea. A systematic metagenomic and bioinformatics analysis identified and quantified genes encoding four dehalogenases and two halogenases, providing fundamental data for the halogen cycle in the Yangtze River water body. The study showed that the microbial community in the Yangtze water body was mainly associated with dehalogenation potential, and the relative abundance of dehalogenase genes was higher than that of halogenase genes. Among the microorganisms with halogenation and dehalogenation potentials, Pseudomonadota and Actinomycetota dominated. Some microorganisms possessed both halogenation and dehalogenation functions, suggesting a potential adaptive strategy to environmental fluctuations. The presence of diverse and complete dehalogenation metabolic pathways highlights the microbial potential for bioremediation. These microorganisms not only contribute to the degradation of halogenated organic matter but also play crucial roles in carbon, nitrogen, and sulfur cycling. This study provides essential data for understanding microbial halogenation and dehalogenation potential in the Yangtze River, offering insights into the microbial-driven biogeochemical cycling mechanisms in its waters.