NUCLEOTIDE-SEQUENCES TRANSFERRED BY GENE CONVERSION IN THE BACTERIUM ACINETOBACTER-CALCOACETICUS

Exchange of nucleotide (nt) sequences between the catIJF and pcaIJF re gions of the Acinetobacter calcoaceticus chromosome appears to contrib ute to frequent repair of mutations, including removal of a Tn5 insert ion from pcaJ. Repaired nt sequences are the products of nonreciprocal genetic exchange. The length of donor catIJF nt tracts recovered in r epaired pcaIJF DNA ranged from less than 315 nt to more than 881 nt. T his evidence does not distinguish gene conversion from natural transfo rmation as a cause of repair, but natural transformation does not appe ar to contribute significantly, because it, unlike the repair process, is inactive in the presence of DNase. High-frequency recombination be tween catIJF and pcaIJF raises the question of why DNA between these c hromosomal regions is stable. It is possible that some of the recombin ational processes associated with gene conversion are unlike those und erlying natural transformation.