CHARACTERISTICS OF PLASMID STABILITY IN BACILLUS-SUBTILIS NB22, AN ANTIFUNGAL-ANTIBIOTIC ITURIN PRODUCER

The stability of plasmids pC194 and pUB110 was investigated in an anti fungal antibiotic iturin producer, Bacillus subtilis NB22. Although pl asmid pC194 was maintained stably over a hundred generations in five s uccesive cultivations in iturin-production no. 3 medium, significant c uring was observed when the cultivation was prolonged for 10 d in the same medium. When the transformant of pC194 was cultivated in Schaeffe r's sporulation medium, drastic curing took place in accordance with t he occurrence of sporulation, even in the presence of an antibiotic fo r selective pressure. In the case of pUB110, in sharp contrast to the result with pC194, high stability was observed in the sporulation medi um, but significant curing was observed during prolonged incubation in no. 3 medium.