Table 6. Empirical results of PCR using different nifH primer sets with DNA from isolates and soils^a.

	AT (°C)b	Dv	Gu	Av	Fs	Ml	Kp	Xa	Rs	Rl	Pn	Ec	AS	LS	NT
F2/R6	51	−	+	+	−	+	+	−	ns	−	−	−	+	+	−
IGK3/DVV	58	+	+	+	+	+	+	+	+	+	+	−	+	+	−
Ueda19F/388R	51	+	+	+	−	+	+	+	+	ns	+	ns	+	+	−
nifH2/R6	44	ns	+	+	+	+	+	ns	−	+	−	ns	s	s	−
nH21f/nifH1	46	ns	Ns	+	−							ns	s	s	−
nifH1/nifH2	46	ns	+	+	−							ns	s	s	−
Ueda19f/univ463r	46	+	ns	+	−	+	+	+	−	+	+	ns	s	s	−
nifH3/nH21f	41	ns	ns	+	−							ns	s	s	−

^aDNA samples and their phylogenetic affiliation in the nifH phylogeny from Figure S2 are: Desulfovibrio vulgaris Hildenborough (Dv), cluster III; Geobacter uraniireducens Rf4 (Gu), subcluster IA; Azotobacter vinelandii DJ (Av), Alpha-, Beta- and Gamma-Proteobacteria; Frankia sp. CcI3 (Fs), Frankia; Mastigocladus laminosus UTEX LB 1931 (Ml), Cyanobacteria; Klebsiella pneumoniae 342 (Kp), Alpha-, Beta- and Gammaproteobacteria; Xanthobacter autotrophicus Py2 (Xa), Alpha-, Beta- and Gammaproteobacteria; Rhodobacter sphaeroides 2.4.1 (Rs), Alpha-, Beta- and Gammaproteobacteria; Rhizobium leguminosarium bv. trifolii (Rl), Alpha-, Beta- and Gammaproteobacteria; Polaromonas naphthalenivorans CJ2 (Pn), Alpha-, Beta- and Gammaproteobacteria; Eschericia coli (Ec), genomic-DNA negative control; agricultural soil (AS); lawn soil (LS); No Template Control (NT). The symbols used are: product of the correct size (+), no product produced (−), non-specific amplification producing multiple bands or a single band of the wrong size (ns), a smeared band of indiscriminate size overlapping in size with the expected product (s). Blank cells indicate that the evaluation was not performed.

^bAnnealing Temperature (AT) used in PCR.