Based upon our earlier studies (A. Tapias, A. R. Fernández de Henestrosa, and J. Barbé, J. Bacteriol. 179:1573-1579, 1997) we hypothesized that the regulatory sequence of the Rhizobium etli recA gene was TTGN₁₁CAA. However, further detailed analysis of the R. etli recA operator described in the present work suggests that it may in fact be GAACN₇GTAC. This new conclusion is based upon PCR mutagenesis analysis carried out in the R. etli recA operator, which indicates that the GAAC and GTAC submotifs found in the sequence GAACN₇GTAC are required for the maximal stimulation of in vivo transcription and in vitro DNA-protein complex formation. This DNA-protein complex is also detected when the GAACN₇GTAC wild-type sequence is modified to obtain GAACN₇GAAC, GTACN₇GTAC, or GAACN₇GTTC. The wild-type promoters of the Rhizobium meliloti and Agrobacterium tumefaciens recA genes, which also contain the GAACN₇GTAC sequence, compete with the R. etli recA promoter for the DNA-protein complex formation but not with mutant derivatives in any of these motifs, indicating that the R. etli, R. meliloti, and A. tumefaciens recA genes present the same regulatory sequence.