Figure 5.

Phylogenetic tree for C1 domain. A phylogenetic tree for the C1 domain—with no genus‐level filter and inclusion of more distant hits (see Methods)—indicates a limited taxonomic distribution of the domain. The largest group of sequences in Chloroflexi places sister to domains found in Nitrospirae, Nitrospinae, and Deltaproteobacteria. Within this clade, the branch along which C1 is inferred to have fused into nitrite reductase genes in Chloroflexi is labeled. C1 homologs that co‐occur in ORFs with nitrite reductase are indicated with magenta diamonds (NirS) or yellow diamonds (NirK). Support values for selected bipartitions are labeled (aLRT/bb). Support for other nodes is indicated with the following color scheme: Strong support with both values ≥90 (black); weak support with both values ≤50 (white); intermediate support with one or both values between 50 and 90 (gray); conflicting support, with one value ≤50 and the other ≥90 (gray). ORF, open reading frame