TABLE 1.

Reference nifH sequences from the GenBank database used in the phylogenetic analyses

Organism or source	GenBank accession no.
Known diazotrophic bacteria
Acetobacter diazotrophicus	AF030414
Alcaligenes faecalis	X96609
Anabaena azollae	L34879
Anabaena sp. strain PCC7120	AF012326
Azoarcus communis	U97116
Azoarcus indigens	U97118
Azoarcus tolulolyticus	U97122
Azospirillum brasilense	M64344
Azotobacter chroococcum	M73020
Azotobacter chroococcum vnfH	X51756
Azotobacter vinelandii	M20568
Azotobacter vinelandii vnfH	M32371
Bradyrhizobium japonicum	E01169, K01620
Chlorobium tepidum	AF065617
Clostridium cellobioparum	U59414
Clostridium pasteurianum	M21537
Desulfobacter curvatus	AF065619
Desulfonema limicola	AF065618
Desulfovibrio gigas	U68183
Frankia alni	L41344
Herbaspirillum seropedicae	Z54207
Klebsiella pneumoniae	J01740
Klebsiella sp.	M63691
Marichromatium purpuratum	AF059648
Methanobacterium thermautotrophicum	AE00916
Methanosarcina barkeri	X56072
Pseudomonas sp.	AF117976
Pseudomonas stutzeri	AF117977, AF117978
Rhizobium leguminosarum biovar phaseoli	M10587
Rhizobium leguminosarum biovar trifolii	K00490
Rhizobium sp.	M16709, M26961
Rhodobacter capsulatus	M15270, X07866
Rhodobacter sphaeroides	AF031817
Rhodospirillum rubrum	M33774
Sinorhizobium meliloti	J01781
Thiobacillus ferrooxidans	M15238
Trichodesmium thiebautii	U23507
Vibrio diazotrophicus	U23650
Unnamed cultivated diazotrophs
Marine microbial mats	AF046827-AF046854, U43438, U43442–U43445
Nonaxenic cyanobacterial cultures	U43436, U43437, U43439
Environmental nifH sequences
Halodule wrightii (shoal grass) rhizoplane	M63688, M63689
Oryza sativa (rice) rhizoplane	D26284-D26306
Douglas Fir forest soil and litter	AF099775–AF099798
Marine microbial mats	U23633–U23646
Marine plankton	AF016592–AF016615, AF016617, AF016618, AF059621–AF059623, AF059629, AF059643–AF059647, U26186
Antarctic diazotrophic microbial consortia	AF049033–AF049040,  AF049043