TABLE 1.

Denitrification capability of soybean bradyrhizobia isolated from two field sites in Japan by the ¹⁵N/GC method^a

Field site (no. of isolates)	Denitri- fication end productb		Species	hupc	HRSd	No. of isolates
	N2	N2O
Nakazaka (n = 42)	+	−	B. japonicum	+	−	22e
	+	−	B. japonicum	−	−	6f
	−	+	B. japonicum	−	−	3g
	−	−	B. japonicum	+	+	2h
	−	−	B. elkanii	−	−	9i
Tokachi (n = 23)	−	+	B. japonicum	−	−	17j
	−	+	B. japonicum	−	+	1k
	−	−	B. japonicum	−	−	1l
	−	−	B. japonicum	−	+	4m

^aSoybean bradyrhizobia previously isolated from Nakazawa and Tokachi field soils were characterized for species, uptake hydrogenase, and repeated sequence fingerprints (9, 18).

^bThe N₂ column indicates completion of the full process of denitrification from ¹⁵NO₃⁻ (2 mM) to ³⁰N₂ with from 98 to 110% recovery after 7 days (+) except for a low recovery (62%) of isolate NC34a. −, the isolate evolved no ³⁰N₂ (<0.03% [vol/vol]). The N₂O column indicates positive (+) and negative (−) N₂O accumulation in the presence of ¹⁴NO₃⁻ (2 mM) after 7 days. ³⁰N₂ and N₂O were determined at least in duplicate.

^cGenotype and phenotype of uptake hydrogenase (16, 18).

^dHRS, highly reiterated sequence-possessing strains carrying high copy numbers of insertion sequences (9, 15, 18, 21).

^eIsolates NC4a, NC5a, NC6a, NC10a, NC11a, NC12a, NC13a, NC14a, NC15a, NC16a, NC17a, NC18a, NC20a, NC21a, NC22a, NC24a, NC26a, NC29a, NC34a, NC35a, NC37a, and NC41a.

^fIsolates NC2a, NC19b, NC27a, NC28a, NC38a, and NC39a.

^gIsolates NC8a, NC33b, and NC36a.

^hIsolates NC3a and NC32a.

ⁱIsolates NC7a, NC23a, NC25a, NC31b, NC42a, NC43a, NC44a, NC45a, and NC46a.

^jIsolates T1, T3, T4, T5, T6, T7, T8a, T9, T10a, T11, T12, T13, T20, T27, T29, T37, and T39.

^kIsolate T25.

^lIsolate T40.

^mIsolates T2, T15, T22, and T31.