Soil texture contributes to shaping comammox Nitrospira communities in rice-wheat rotation soils

Complete ammonia oxidizers (comammox Nitrospira) are intriguing discoveries that mark a significant milestone in the global nitrogen cycle. While numerous soil physiochemical variables have been identified as key influencers of comammox Nitrospira distribution, the role of soil texture in shaping these communities remains largely uncertain. Here, we explored the diversity, community structure of comammox Nitrospira, and their driving factors, including soil texture in 237 rice-wheat rotation soils. The results indicated that soil pH and texture were the primary factors influencing the Shannon diversity and richness of comammox Nitrospira. Comammox Nitrospira Shannon diversity and richness were positively associated with soil pH and silt content, but negatively correlated with clay content, suggesting that finer-textured soils harbored lower comammox Nitrospira diversity. Additionally, silt content emerged as the second most influential factor, after pH, shaping comammox Nitrospira community structure. Clade A.2 was found as the predominant comammox Nitrospira clade in rice-wheat rotation soils, representing 59.3 % of the total sequences. Clade A.2 exhibited a positive correlation with sand and clay contents but a negative association with silt content. Conversely, Clades A.3 and B demonstrated the opposite pattern. Overall, our study underscores the critical role of soil texture as a mediator of comammox Nitrospira diversity and community structure, emphasizing the need to consider soil texture in investigations of comammox Nitrospira.