TABLE 1.

Strains and characteristics

Straina	Small-subunit rRNA patternsb	R. tropici plasmidsc	nifH gened	Acetylene reduction activity with P. vulgaris nodules (nmol of ethylene/h/plant)e
				14 days postinoculation	18 days postinoculation
E. adhaerens transconjugants
CFNEA40	ACEGIK	a, cf	+	102.7	NDg
CFNEA41	ACEGIK	a, b, c	+	104.8	ND
CFNEA50	ACEGIK	a, c	+	108.0	84.9
CFNEA51	ACEGIK	a, c	+	106.9	85.9
CFNEA52	ACEGIK	a, b, cf	+	103.8	84.9
CFNEA53	ACEGIK	a, b, c	+	115.3	96.4
CFNEA54	ACEGIK	b, c	+	113.2	94.3
CFNEA55	ACEGIK	b, c	+	126.9	104.8
CFNEA56	ACEGIK	b, c	+	114.3	94.3
E. adhaerens ATCC 33499	ACEGIK
R. tropici strains
CFN299	BDFHJL		+
CFN299 Tn5-mob-6					166.8
CFN299 Tn5-mob-7					182.4

^aOnly transconjugant CFNEA41 was derived from CFN299 Tn5-mob-7; all other transconjugants were derived from CFN299 Tn5-mob-6. R. etli CFN42 was also used in this study. 

^bThe different letters represent distinct patterns obtained with restriction enzymes HinfI, MspI, RsaI, HhaI, Sau3A1, and DdeI; each letter position refers to a different restriction enzyme used for PCR-synthesized 16S rRNA genes (15) obtained with primers rD1 and fD1 (29). 

^cEckhardt gel analysis was performed as modified (23) with liquid early-exponential-phase cultures in horizontal gels with sodium dodecyl sulfate in the agarose. The plasmid sizes were as follows: plasmid a, 185 kb; plasmid b, 220 kb; and plasmid c, 500 kb (nod and nif plasmid). 

^dThe presence of nifH was determined by Southern blot hybridization or by PCR synthesis with nif primers as described previously (6). 

^eAcetylene reduction activity was determined 14 and 18 days postinoculation. The data are averages for five plants from one experiment. The plant-to-plant variation was not more than 10% for each transconjugant. The levels of nitrogen fixation with the E. adhaerens transconjugants were around 40% of the levels with the parental CFN299 strains in the four other experiments. Plants were maintained in a growth chamber at 28°C. 

^fPlasmid cointegration or rearrangement occurred, which led to an approximately 700-kb plasmid or to an additional 300-kb plasmid. 

^gND, not determined.