The recent discovery of complete ammonia oxidation (comammox) has increased our understanding of nitrification. Although comammox has been shown to play an important role in plain wetland ecosystems, studies of comammox contribution are still limited in plateau wetland ecosystems. Here, we analyzed the abundance, activity, community and biogeochemical mechanisms of the comammox bacteria in Yunnan-kweichow and Qinghai-Tibet plateau wetlands from elevations of 1000-5000 m. Comammox bacteria were widely distributed in all 16 sediment samples with abundances higher than 0.96 ± 0.26 × 10⁷ copies g⁻¹ (n = 16). Comammox showed high activity (1.18 ± 0.17 to 1.98 ± 0.08 mg N kg⁻¹ d⁻¹) at high-elevation (3000-5000 m) and dominated the nitrification process (activity contribution: 37.20 - 60.62%). The activity contribution of ammonia-oxidizing bacteria (1.07 ± 0.08 to 2.79 ± 0.35 mg N kg⁻¹ d⁻¹) dominated the nitrification process (44.55 - 64.15%) in low-elevation (1000-3000 m) samples. All detected comammox Nitrospira belonged to clade A, while clade B was not detected. Elevation always had a strongest effect on key comammox species. Thus, we infer that elevation may drive the high relative abundance of the species Candidatus Nitrospira nitrificans (avg. 12.40%) and the low relative abundance of the species Nitrospira sp. SG-bin2 (avg. 4.75%) in high-elevation samples that showed a high comammox activity (avg. 1.62 mg N kg⁻¹ d⁻¹) and high contribution (avg. 46.08%) to the nitrification process. These results indicate that comammox may be an important and currently underestimated microbial nitrification process in plateau wetland ecosystems.

最近发现完全氨氧化（comammox）增加了我们对硝化作用的理解。尽管已证明 comammox 在平原湿地生态系统中发挥重要作用，但对 comammox 贡献的研究在高原湿地生态系统中仍然有限。在这里，我们分析了海拔1000-5000 m的云贵州和青藏高原湿地comammox细菌的丰度、活性、群落和生物地球化学机制。Comammox 细菌广泛分布在所有 16 个沉积物样品中，丰度高于 0.96 ± 0.26 × 10 ⁷拷贝 g ^-1 ( n  = 16)。Comammox 显示出高活性（1.18 ± 0.17 至 1.98 ± 0.08 mg N kg ^-1 d ^-1) 在高海拔 (3000-5000 m) 并主导硝化过程（活性贡献：37.20 - 60.62%）。氨氧化细菌的活性贡献（1.07 ± 0.08 至 2.79 ± 0.35 mg N kg ^-1 d ^-1）在低海拔（1000-3000 m）样品中主导硝化过程（44.55 - 64.15%）。所有检测到的comammox Nitrospira属于进化枝A，而未检测到进化枝B。海拔总是对关键的 comammox 物种产生最强的影响。因此，我们推断海拔可能会导致硝化硝化假丝酵母物种的高相对丰度（平均 12.40%）和硝化螺菌物种的低相对丰度。SG-bin2（平均 4.75%）在显示出高 comammox 活性（平均 1.62 mg N kg ^-1 d ^-1）和对硝化过程的高贡献（平均 46.08%）的高海拔样品中。这些结果表明，comammox 可能是高原湿地生态系统中一个重要且目前被低估的微生物硝化过程。