Induction of Two Types of Gene Amplification by a Cloned DNA Fragment and Amplification of a Foreign Gene on the Bacillus subtilis Chromosome by Using the Fragment

Abstract

In our previous work we cloned on λ Charon4A phage vector a 6. 4-kb EcoRI fragment, which had the transforming activity of inducing gene amplification with a 16-kb repeating unit on the Bacillus subtilis chromosome by competence transformation ; those transformants were selected as tunicamycin resistant (Tm^r) transformants. We found that this DNA fragment can induce another type of gene amplification with a 8. 7-kb repeating unit by transformation when we use an amyE07 mutant as a recipient cell and select both Tm^r and amyE⁺ transformants. In the latter (8.7-kb type) gene amplification, the copy number was increased up to 20 in contrast to about 10 copies in the former 16-kb type. We replaced a part of the 6.4 kb EcoRI fragment with a cat gene as a model of a foreign gene, and succeeded in the amplification of the cat gene on the chromosome by the latter type of transformation.