Bacillus subtilis generates a major specific deletion in pAM beta 1.

pAM beta 1, a 26.5-kilobase plasmid originally isolated from Streptococcus faecalis, was conjugally transferred from Streptococcus lactis to Bacillus subtilis. No conjugal transfer of pAM beta 1 from B. subtilis to S. lactis was observed. In addition, pAM beta 1 which had been reintroduced in S. lactis after cycling through B. subtilis had lost its conjugal transferability to Streptococcus cremoris, although under the same conditions noncycled pAM beta 1 was transferred at high efficiency. Restriction and Southern blot analyses showed that pAM beta 1 had suffered one major, specific 10.6-kilobase deletion and several minor but also specific deletions in B. subtilis. Comparing the major deletion derivative, delta pAM beta 1, with B. subtilis strains which have been reported to contain pAM beta 1 showed that these strains also contained delta pAM beta 1. Hybridization experiments showed that the deleted fragment was not transposed to the B. subtilis chromosome. Based on the size of the minor deletion derivatives from pAM beta 1, it is suggested that these use a different origin of replication in B. subtilis.