Linkage and segregation of a mating type specific phage and resistance characters in nocardial recombinants.

ECOMBINATION of auxotrophic and inhibitor resistant characters from crosses of Nocardia canicruria and Nocardia erythropolis have been previously reported (ADAMS and BRADLEY 1963; ADAMS 1964; BROWNELL and ADAMS 1967). Substrains derived from N . canicruria were observed to mate only with substrains derived from N . erythropolis while substrains of homologous origin were incompatible. From these observations it is apparent that some type of mating factor(s) controls compatibility in these organisms. To elucidate the mechanisms involved during recombination and gain knowledge of the gene (s ) responsible for compatibility, construction of linkage maps was initiated (BROWNELL and ADAMS 1967). During those investigations, nocardiophage +C was isolated from soil. This phage infected only N . canicruria strains and suggested a possible relationship between mating type and +C sensitivity. The general characterization and conditions necessary for optimal reproduction of the +C phage have been reported (BROWNELL, ADAMS and BRADLEY 1967). Since N . erythropolis is resistant to infection by +C, recombinants obtained from matings of N . canicruria and N . erythropolis can be analyzed for segregation of +C sensitivity and for their fertility in backcrosses to the parental types from which they were derived. Thus, the present work allowed a correlation OI phage +C sensitivity with mating behavior of recombinants and suggested a genomal location for the mating factors. The addition of chloramphenicol resistance markers in strains previously mapped, permitted the confirmation and clarification of linkage relationships previously reported for these strains (BROWNELL and ADAMS 1967). With the clearer linkage map herein presented, and preliminary recognition of chromosomal location of mating factors responsible for fertility. a new tool for investigation of bacterial conjugational phenomena, nocardia1 recombination, is more firmly established.