TABLE 2.

Percent similarities of Spartina rhizosphere NifH amino acid sequences to the most similar sequence(s) from known diazotrophic bacterial species^a

Spartina sequence	Organism with most similar sequence(s)	% Similarity
Presumed γ-Proteobacteria
A2	Azotobacter chroococcum	94.2
B2	Azoarcus indigens	97.3
B5	Azoarcus indigens	97.3
BP2, HD2-4	Pseudomonas stutzeri	97.5
BP3, HD4-1, HD4-2, X1, X3, X5, X8, Y1, Y2	Pseudomonas stutzeri	98.3
BP4	Pseudomonas stutzeri	96.6
C1	Azotobacter chroococcum	96.4
E2, E4, F5, F9	Azomonas agilis, Azotobacter chroococcum, Klebsiella sp., Marichromatium purpuratum	93.5
F1	Azomonas agilis, Azotobacter chroococcum	87.8
F2	Azoarcus indigens	95.6
F3	Klebsiella sp.	92.5
F4	Marichromatium purpuratum	92.5
F6	Marichromatium purpuratum	90.7
F7	Marichromatium purpuratum	91.6
F8	Marichromatium purpuratum	89.7
HD2-2, X7	Azotobacter chroococcum, Azotobacter vinelandii	85.6
HD2-3	Azoarcus indigens	92.9
HD3-6	Marichromatium purpuratum	89.7
HD3-8	Pseudomonas stutzeri	97.5
X2	Pseudomonas stutzeri	98.3
X6	Pseudomonas stutzeri	95.8
Y3	Pseudomonas stutzeri	94.1
Y4	Azotobacter chroococcum	95.0
JC110	Klebsiella sp., Vibrio diazotrophicus	97.2
SG21	Azomonas agilis, Azotobacter chroococcum	95.0
TS210	Pseudomonas stutzeri	96.6
Presumed α-Proteobacteria
A4	Azoarcus tolulolyticus	95.5
E1	Bradyrhizobium japonicum	87.0
G1	Azospirillum brasilense, Sinorhizobium meliloti	90.6
G2	Azospirillum brasilense	90.6
G3	Azospirillum brasilense, Sinorhizobium meliloti	92.0
G4	Azospirillum brasilense	92.8
SC16	Acetobacter diazotrophicus, Herbaspirillum seropedicae, Rhizobium sp. M16709	93.5
Presumed anaerobes
A1	Desulfonema limicola	87.6
A3	Desulfonema limicola	88.6
A5	Desulfonema limicola	85.7
B1	Desulfonema limicola	90.5
B3, HD1-1	Desulfovibrio gigas	84.2
B4	Desulfonema limicola	87.6
D1, D2, HD3-1, HD3-2	Desulfovibrio gigas	83.5
HD2-1	Desulfonema limicola	85.7
HD3-3	Desulfonema limicola	88.6
HD3-4	Desulfovibrio gigas	84.1
HD3-5	Desulfonema limicola	86.7
HD3-7	Desulfobacter curvatus	88.8
X4	Desulfonema limicola	90.5

^aPercent similarities are from the distance matrix constructed in PAUP* (version 4.0b2). Spartina sequences are listed by the DGGE gel bands from which they were recovered (see Materials and Methods) and grouped into the major sequence clusters shown in Fig. 2 to 4. Note that these clusters are named for the predominant types of organisms they contain, but some sequences from other phylogenetic groupings can occur. Pure culture isolates from the Spartina rhizoplane are also included.