RECOMBINATION BETWEEN NOCARDIA ERYTHROPOLIS AND NOCARDIA CANICRURIA.

Adams, James N. (University of South Dakota, Vermillion). Recombination between Nocardia erythropolis and Nocardia canicruria. J. Bacteriol. 88:865-876. 1964.-Nutritionally complementary auxotrophic mutants derived from Nocardia erythropolis did not yield prototrophic recombinants when progeny from mixed cultures or newly mixed strains were inoculated onto minimal medium. Similarly, complementary auxotrophic mutants of N. canicruria did not produce prototrophic recombinants. When interspecific mating was attempted between complementary mutants of N. erythropolis and N. canicruria, prototrophic recombinants were recovered at frequencies dependent, in part, upon the auxotrophic strains used in the test crosses. Growth of the parental types in mixed cultures was necessary for the production of recombinant progeny. Direct selection for recombinants by inoculating the selective medium with a mixture of parental types without prior mixed growth did not result in the recovery of recombinants. Varying the medium upon which mixed growth occurred, or varying the ratio of N. erythropolis to N. canicruria cells used as inocula, did not greatly affect the recovery of recombinants. Heat-killing one or the other of the parental types prevented recombinant production. The lack of recovery of recombinants from crosses of homologously derived strains suggested that a mating factor controls recombination. The mating factor was not eliminated by acriflavine treatment. The recovery of a recombinant strain capable of forming recombinants with either N. erythropolis or N. canicruria, and the recovery of another strain which mated only with N. erythropolis in backcrosses, suggests that the mating factor may be of a multiple nature.