Fig. S2. Neighbor-joining phylogenetic tree of betaproteobacterial amoA nucleotide sequences of the clones retrieved from BC samples. AmoA of Nitrosomonas species and environmental clones detected as the best BLASTn hits were used as reference sequences. Nitrosospira multiformis ATCC 25196 was used for the outgroup. The numbers at nodes represent bootstrap values (%, 1000 resampling); only the values greater than 50% are indicated. 


Table S2 .

 S2 Phylogenetic information of comammox amoA OTUs and their corresponding accession number 


		Table S3. The activated sludge and biofilm content
		in each tank solution		
	OTU	Number of clone	Accession number of clone tank BC	Closest BLAST match AO	MA	Accession number of BLAST match A, MA, and AO A
	OTU1 OTU2 OTU3	40	LC503632-LC503671 LC503675-LC503682 LC503672-LC503674 activated sludge Uncultured Nitrospira sp. clone OTU52 Uncultured microorganism clone WH16082200144, pmoA Uncultured Nitrospira sp. clone OTU1 content (g L -1 ) 39 42 6.9	MK290956 MH638925 MG387156
	OTU4 OTU5		LC503683, LC503684 LC503685, LC503686 biofilm content (g L -1 )	Uncultured bacterium clone coma_amoA_A-1 Uncultured Nitrospira sp. clone OTU1 --	34	MH444516 MG387156
	OTU6		LC503687	Uncultured Nitrospira sp. clone OTU1		MG387156
	OTU7		LC503688	Uncultured Nitrospira sp. clone OTU1		MG387156
	OTU8		LC503689	Uncultured Nitrospira sp. clone OTU1		MG387156
	OTU9		LC503690	Uncultured Nitrospira sp. clone OTU1		MG387156
	OTU10		LC503691	Uncultured Nitrospira sp. clone OTU1		MG387156
	Fig. S1. Melting curve analysis (A) and agarose gel electrophoresis (B)
	after qPCR of comammox amoA gene. Arrows indicate extra bands.