[Escherichia coli K-12 mutants with increased resistance to ionizing radiation. I. Isolation and study of cross resistance to different agents].

The strains of Bacillus subtilis actively exchange genetic material during joint incubation on a properly composed selective solid medium at 37 degrees C. Predominantly, colonies of multiple recombinants are formed. If DNase is present in the medium, total number of recombinant colonies and the share of colonies of multiple recombinants decrease. At 46 degrees C the recombination process is inhibited. The results obtained are discussed using two hypotheses: 1) a donor cell transfers a significant part or even whole chromosome to a neighbouring recipient cell, 2) recombinations occur successively in mini-clones of intermediate recombinants. It is suggested that the phenomenon observed is close to the natural genetic transformation in Bac. subtilis.