Prediction, identification, and artificial selection of DNA rearrangementsin Rhizobium: Toward a natural genomic design

Based on the DNA sequence of the symbiotic plasmid of Rhizobium strain NGR2 34, we predicted potential rearrangements generated by homologous recombina tion. All predicted rearrangements were identified experimentally by using a PCR-based methodology. Thus, the predicted and the actual dynamic maps of the replicon coincide. By using an approach that does not involve the intr oduction of exogenous genetic elements, derivative populations that are pur e for specific rearrangements were obtained. We propose that knowledge of t he DMA sequence of a genome offers the possibility of designing pathways of sequential rearrangements leading to alternative genomic structures. An ex perimental strategy to isolate bacterial populations containing the desired structures is discussed.