TABLE 1.

Numbers of prokaryotic species and strains harboring T1-nifH, T2-nifH but no T1-nifH, and T3-nifH on the genomes from RefSeq and KEGG, with or without a previous report on diazotrophic activity

Database	Strain or species chararacteristic	No. of prokaryotic species and strains
		Diazotrophic activity reported	No diazotrophic activity reported/not yet investigated
RefSeq	Harboring T1-nifH on their genomes	1,600	4,149
	Harboring T2-nifH but not T1-nifH on their genomes	337	111
	Harboring T3-nifH on their genomes	0	236
KEGG	Harboring T1-nifH on their genomes	132	444
	Harboring T2-nifH but not T1-nifH on their genomes	14	6
	Harboring T3-nifH on their genomes	1	71