FIG. 3.

Southern blot of restriction digests of genomic DNA to demonstrate a change in the band size of the putative insertion mutation relative to the parental type, indicative of insertion of ermC into sarT. P, parental; M, sarT mutant. ClaI cleaves sarT but not ermC; the 3.2-kb sarT DNA probe hybridizes with a 5.6- and a 2.2-kb fragment, while the 1-kb sarT DNA probe hybridizes only with the 5.6-kb fragment. Insertion of ermC increases the larger fragment to 6.9 kb. There is a single XmnI site within ermC. XmnI yields a 4.0-kb fragment encompassing sarT. With the ermC insert, expected fragment sizes are 2.2 and 3.1 kb. The 2.6- and 5-kb fragments seen in panel A are consistent with incomplete enzyme digestion.