Effects of temperature on plasmid stability and penicillinase productivity in a transformant of Bacillus stearothermophilus

After transforming host cells of Bacillus stearothermophilus CU21 with a recombinant plasmid pLP11 that harbored constitutive penicillinase genes of B. licheniformis CO1, both the stability of the plasmid and specific rate of penicillinase production were studied. The temperature at which the plasmid could be kept in a stable fashion in the transformant of B. stearothermophilus CU21 (pLP11) ranged nearly from 44 to 50 degrees C, irrespective of batch and continuous cultures. Continuous and steady-state cultures of the transformant could only be realized within this narrower temperature range. Indeed, the approximate temperature ranges of growth for the host and transformant were from 40 to 70 degrees C and from 40 to 63 degrees C, respectively. Clearly, the upper limit for the growth temperature of host cells decreased when they were transformed. Kinetic patterns of penicillinase production in continuous culture of the transformant (with plasmid) from 44 to 50 degrees C differed remarkably from that of B. licheniformis CO1 (without plasmid) at 37 degrees C.