[Integration of the plasmid carrying the genes for tryptophan metabolism of Bacillus mesentericus into the chromosome of Bacillus subtilis].

Integration of several tryptophan operon genes from Bacillus mesentericus into the chromosome of Bac. subtilis was carried out. The genetic material exchange between these two species is usually impossible in the process of transformation, because of poor homology. The integration only took place after the genes of Bac. mesentericus were introduced in Bac. subtilis cells on a hybrid plasmid. Plasmid markers also integrated into the chromosome, together with heterologous DNA. The integration occurred in the region of Bac. subtilis tryptophan operon, which is likely to be due to retained homology between corresponding DNAs. The integration acts occurred during prolonged maintenance of chimeric plasmid in autonomously replicating form. We suggest to designate this phenomenon "retarded homologous recombination".