The recovery of nocardial recombinants from broth cultures

Abstract

Broth culture media were examined for their ability to support growth and recombination between compatible strains of Nocardia erythropolis. Nutrient (Nut) and peptone – yeast-extract (PY) broths supported the production of recombinants after 36 h of incubation with a maximum recovery of about 6.0 × 10−1 CFU/ml. Cells mated in trypticase broth (TB) yielded the highest incidence of recombinants (1.0 × 10−2 CFU/ml) in the absence of parental cell growth. From a chemically defined mating broth (CD), supplemented with limited amounts of the parental-growth requirements, recombinant recovery reached about 1.0 × 10−4 after 120 h of incubation. The recombinant class types obtained from Nut- or PY-mated strains were predominantly auxotrophic while TB-mated strains produced stable prototrophs. The high incidence of recombinant types from TB-mated strains was due to growth of selected prototrophic classes. Studies with strains mated in PY broth indicate that the mating event occurs at very low frequencies between older, stationary-phase cells rather than between actively growing, log-phase cells.