Table 1. Elements of N-metabolism that are shared by bacteria and eukaryotes.
| Taxonomic group and organism | NAD(P)H dependent, assimilatory | PQQ-dehydrogenase | ||
| NirB | NirBD | NiaD-related proteins | MxaF | |
| methanotrophs & methylotrophs | ||||
| Methylocystis sp. SC2 | yes | 1 domain | yes | |
| Methylocystis parvus | precursor & 1 domain | yes | ||
| Methylosinus trichosporium OB3b | yes | 1 domain | yes | |
| Methylosinus sp. LW4 | 1 domain | yes | ||
| Methylocella silvestris BL2 | yes | 1 domain | yes | |
| Beijerinckia indica * | yes | precursor & 2 domains | yes | |
| Microvirga sp. WSM3557 | yes | yes | ||
| Methylobacterium extorquens DM4 | 3 domains | yes | ||
| Methylobacterium extorquens PA1 | 3 domains | yes | ||
| Methylobacterium extorquens AM1 | 2 domains | yes | ||
| Methylobacterium extorquens CM4 | yes | |||
| Methylobacterium extorquens DSM 13060 | yes | |||
| Methylobacterium nodulans ORS 2060 | 2 domains | yes | ||
| Methylobacterium populi BJ001 | 2 domains | yes | ||
| Methylobacterium radiotolerans JCM 2831 | 2 domains | yes | ||
| Methylobacterium mesophilicum SR1.6/6 | 2 domains | yes | ||
| Methylobacterium sp. GXF4 | 2 domains | yes | ||
| Methylobacterium sp. 88A | 2 domains | yes | ||
| Methylobacterium sp. 4–46 | yes | |||
| Xanthobacter autotrophicus Py3 | yes | yes | ||
| Hyphomicrobium denitrificans 1NES1 | yes | yes | ||
| Bradyrhizobiaceae | ||||
| Nitrobacter winogradskyi Nb-255 | yes | |||
| Nitrobacter hamburgensis X14 | yes | |||
| Nitrobacter hamburgensis sp. Nb-255 | yes | |||
| Oligotropha carboxidovorans OM4 & OM5 | yes | |||
| Rhodopseudomonas palustris BisA53 | 2 domains | yes | ||
| Rhodopseudomonas palustris BisB18 | 1 domain | yes | ||
| Rhodopseudomonas palustris TIE-1 | 2 domains | |||
| other 4 Rhodopseudomonas palustris | 1 domain | |||
| Rhodospirillales | ||||
| Granulibacter bethesdensis CGDNIH1 | yes | 2 domains | yes | |
| Commensalibacter intestini A911 | yes | |||
| Acidocella sp. MX-AZ02 | yes | 1 domain | ||
| Acidiphilium multivorum AIU301 | yes | |||
| Acidiphilium cryptum & sp. PM | yes | 1 domain | ||
| Gluconobacter oxydans H24 | yes | precursor & 2 domains | ||
| Gluconobacter frateurii NBRC 103465 | yes | precursor | ||
| Gluconacetobacter oboediens 174Bp2 | yes | precursor & 2 domains | ||
| Acetobacter pasteurianus IFO 3283-01/32 | yes | precursor | ||
| Acetobacter aceti | yes | precursor & 1 domains | ||
| Gluconacetobacter europaeus LMG 18494 | yes | precursor | ||
| Gluconacetobacter diazotrophicus PAI5 | 2 domains | |||
| Acetobacter pomorum DM001 | yes | |||
| Acetobacter tropicalis NBRC 101654 | yes | |||
| Asaia platicody | yes | precursor | ||
| Saccharibacter sp. | yes | 2 domains | ||
| Tistrella mobilis KA081020–065 | yes | 2 domains | ||
| Azospirillum lipoferum 4B | yes | 1 domain | yes | |
| Azospirillum amazonense Y2 | yes | |||
| Azospirillum brasilense Sp245 | yes | |||
| Azospirillum sp. B510 | yes | |||
| Caenispirillum salinarum AK4 | yes | |||
| Thalassospira profundimaris WP0211 | yes | |||
| Thalassospira xiamenensis M-5 | yes | |||
| Magnetospirillum magneticum AMB-1 | yes | |||
| Magnetospirillum sp. SO-1 | yes | |||
| Magnetospirillum gryphiswaldense MSR-1 | yes | |||
| Rhodobacterales | ||||
| Oceanicola granulosus | 1 domain | |||
| Oceanicola sp. S124 | yes | |||
| Octadecabacter antarcticus 307 | yes | |||
| Paracoccus denitrificans PD1222 | yes | |||
| Roseobacter denitrificans OCh114 | yes | |||
| Roseobacter litoralis Och 149 | yes | |||
| Jannaschia sp. CCS1 | yes | |||
| Rhizobiales (other) | ||||
| Martelella mediterranea | precursor | |||
| Aureimonas ureilytica | 2 domains | |||
| Sinorhizobium meliloti 1021 | yes | 2 domains | ||
| Rhizobium leguminosarum bv. trifolii WSM1325 | yes | |||
| other 32 Rhizobiales | yes | |||
| Sphingomonadales & Caulobacterales | ||||
| Novosphingobium nitrogenifigens | precursor | |||
| Sphingomonas sp. 17 | 2 domains | |||
| Sphingomonas sp. PAMC26621 | 1 domain | |||
| Sphingopyxis alaskensis RB2256 | yes | |||
| other 19 Sphingomonadales & 6 Caulobacterales | yes | |||
| total α-proteobacteria | ca. 100 | 10 | 12 precursors | |
| Eukaryotes | ||||
| Aspergillus fumigatus | yes | yes | ||
| other 130 fungi (predominantly Ascomycetes) | yes | yes | ||
| Ectocarpus silicosus | yes | yes | ||
| plus other 8heterokonts | (1 yes) | yes | yes | |
| Aureococcus anophagefferens | yes | yes & 2 domains | ||
| Acanthamoeba castellani | yes | |||
| total Eukaryotes | 1 | 140 | 141 | |
Proteins closely related to NirB, NirBD, NiaD and MxaF are annotated as yes, or precursor in the case of Nas/CysJ nitrate reductase (Fig. 2). The column of NiaD-related proteins also lists the number of NiaD domains that have homologues proteins in each organism, e.g. flavohaem (cf. Fig. 2C).
*Its close relative Beijerinckia mobilis has been reported to grow on methanol and possess MxaF.