Although the distribution of ammonia/nitrite oxidizers had been profiled in different habitats, current understanding is still limited regarding their niche differentiation in the integrated biofilm reactors, the symbiotic associations of ammonia/nitrite oxidizers, as well as the parasitic interaction between viruses and those functional organisms involved in the nitrogen cycle. Here, the integrated metagenomics and metatranscriptomics are applied to profile the ammonia/nitrite oxidizers communities and transcriptional activities changes along the flowpath of a concatenated full-scale rotating biological contactor (RBC) (frontend Stage-A and backend Stage-B). 19 metagenome-assembled genomes (MAGs) of ammonia/nitrite oxidizers were recovered by using a hybrid assembly approach, including four ammonia-oxidizing bacteria (AOB), two ammonia-oxidizing archaea (AOA), two complete ammonia oxidation bacteria (comammox), eight nitrite-oxidizing bacteria (NOB), and three anaerobic ammonium oxidation bacteria (anammox). Diverse AOB and anammox dominated Stage-A and collectively contributed to nitrogen conversion. With the decline of ammonia concentration along the flowpath, comammox and AOA appeared and increased in relative abundance in Stage-B, accounting for 8.8% of the entire community at the end of this reactor, and their dominating role in nitrogen turnover was indicated by the high transcription activity of their corresponding function genes. Moreover, the variation in the abundance of viruses infecting ammonia and nitrite oxidizers suggests that viruses likely act as a biotic factor mediating ammonia/nitrite oxidizer populations. This study demonstrates that complex factors shaped niche differentiation and symbiotic associations of ammonia/nitrite oxidizers in the RBC and highlights the importance of RBCs as model systems for the investigation of biotic and abiotic factors affecting the composition of microbiomes.

尽管氨/亚硝酸盐氧化剂的分布已在不同的栖息地进行了描述，但目前对它们在综合生物膜反应器中的生态位分化、氨/亚硝酸盐氧化剂的共生关联以及病毒与那些功能性病毒之间的寄生相互作用的了解仍然有限。参与氮循环的生物。在这里，集成的宏基因组学和宏转录组学用于分析氨/亚硝酸盐氧化剂群落和转录活动沿串联全尺寸旋转生物接触器 (RBC)（前端阶段 A 和后端阶段 B）的流动路径的变化。通过使用混合组装方法回收了 19 个氨/亚硝酸盐氧化剂的宏基因组组装基因组 (MAGs)，其中包括四种氨氧化细菌 (AOB)，2 个氨氧化古细菌 (AOA)、2 个完全氨氧化细菌 (comammox)、8 个亚硝酸盐氧化细菌 (NOB) 和 3 个厌氧氨氧化细菌 (anammox)。不同的 AOB 和 anammox 在 A 阶段占主导地位，共同促成了氮的转化。随着沿流路氨浓度的下降，comammox 和 AOA 在 B 阶段出现并相对丰度增加，占该反应器末端整个群落的 8.8%，它们在氮周转中的主导作用由其相应功能基因的高转录活性。此外，感染氨和亚硝酸盐氧化剂的病毒丰度的变化表明，病毒可能充当介导氨/亚硝酸盐氧化剂种群的生物因子。