FIG. 4.

PCR products obtained directly from nodule extracts. Each surface-sterilized nodule was squeezed in 0.1 ml of sterilized water and extracted twice with phenol-chloroform-isoamyl alcohol and once with chloroform; the resulting preparation was precipitated with ethanol and resuspended in 15 μl of H₂O, and 5-μl aliquots were used either with R. tropici citrate synthase gene primers (see text) (A) or with nifH gene primers (6) (B). Lanes 1 to 4, nodules formed by R. tropici strain CFN299; lane 5, R. tropici CFN299 DNA; lane 6, no-DNA control; lane 7, 1-kb DNA ladder marker; lanes 8 to 12, nodules from E. adhaerens transconjugants (lanes 8 and 9, CFNEA51; lane 10, CFNEA53; lanes 11 and 12, CFNEA51), lane 13, E. adhaerens ATCC 33499 DNA.