TRANSFORMATION IN ASPERGILLUS-OCHRACEUS

Mutants (lysine requiring) of Aspergillus ochraceus were kept under st arvation conditions for 15 days and finally were treated with DNA of a 40-h-old culture of the wild strain. The donor DNA-treated mutant con idia were then grown on plates containing minimal medium at 28 degrees C for 4 days. The number of transformed cells was estimated by colony counting and hence percentage transformants. The transforming activit y of the donor DNA was found to be inhibited by the action of heat and variation of pH, and also varied with the period of starvation and wi th the concentration of donor DNA.