Table 1. Frequency table of nirK (K), nirS (S) and nosZ (Z) co-occurrence types and taxonomic affiliation at phylum level as well as the percentage of organisms within each phylum that also harbor a nor gene.

Phylum	K	%nor	KS	%nor	KSZ	%nor	KZ	%nor	S	%nor	SZ	%nor	Z	%nor
Actinobacteria	102↑	42	0	-	0	-	0↓	-	0	-	0↓	-	0↓	-
Aquificae	0	-	0	-	0	-	0	-	0	-	2↑	100	0	-
Ascomycota	27↑	67	0	-	0	-	0↓	-	0	-	0	-	0↓	-
Bacteroidetes	8↓	100	0	-	1	0	24↑	67	0	-	0↓	-	24↑	17
Chlorobi	0	-	0	-	0	-	0	-	0	-	0	-	2↑	0
Chloroflexi	5	0	0	-	0	-	1	0	2↑	0	0	-	2	0
Crenarchaeota	0	-	0	-	0	-	0	-	2↑	100	2↑	100	0	-
Deferribacteres	0	-	0	-	0	-	0	-	0	-	0	-	1↑	0
Deinococcus-Thermus	0↓	-	2↑	100	0	-	0	-	3↑	100	0	-	0	-
Euryarchaeota	5	60	0	-	0	-	4	100	0	-	0	-	5↑	0
Firmicutes	16	25	0	-	0	-	4	100	0	-	1	100	8↑	12
Gemmatimonadetes	0	-	0	-	0	-	1	0	0	-	0	-	0
Nitrospirae	1	0	0	-	0	-	0	-	1↑	100	0	-	0
Planctomycetes	1	0	0	-	0	-	0	-	0	-	0	-	0
Proteobacteria	135↓	66	2	100	5	100	96↑	96	12	92	74↑	99	47	51
Spirochaetes	2	50	0	-	0	-	3	33	0	-	1	100	3	67
Thaumarchaeota	9↑	0	0	-	0	-	0	-	0	-	0	-	0	-
Verrucomicrobia	3	67	0	-	0	-	1	0	0	-	0	-	2	0

Residuals are according to Pearson Chi-squared test (P<0.001).

^↑Combinations with Pearson residuals >2.

^↓Combinations with Pearson residuals <−2.