Abundance and community structure of comammox bacteria in the rhizosphere of aquatic plants in an urban eutrophic lake

Different from ammonia oxidizing archaea and ammonia oxidizing bacteria, complete ammonia oxidation (comammox) bacteria can directly oxidize ammonia to nitrate. Hence, it is necessary to clarify the distribution of comammox bacteria in water bodies. Aquatic plants, whose roots can provide favorable conditions for nitrification, are often used to remediate polluted lakes. This study investigated the community structure of comammox bacteria in the rhizosphere of four aquatic plants in Lake Yuehu, an urban eutrophic lake. The results showed that the abundance of comammox bacteria in the near-rhizosphere of most aquatic plants was higher than that in the far-rhizosphere, suggesting that the aquatic plants promote the rhizosphere abundance of comammox bacteria in eutrophic lakes. Both clade A and clade B of comammox bacteria were present in the Lake Yuehu, with the former showing greater dominance. Co-occurrence network analysis revealed that two subclades of clade A had opposite network parameters in the near-rhizosphere and far-rhizosphere. Redundancy analysis (RDA) analysis showed that OM, pH and NON of sediment were correlated with the abundance of comammox bacteria, which were the main environmental factors affecting the growth of this microorganism. These results suggest that aquatic plants affected the distribution and diversity of comammox bacteria in sediments, which may result in changes in the process of ammonia oxidation and eutrophication in water.