FIG. 2.

Confirmation of virB gene deletions by Southern blotting. FspI-digested genomic DNA from wild-type B. abortus 2308 and each of its isogenic mutants was electrophoresed and transferred to nylon membranes. Membranes were probed with DNA fragments corresponding to genes listed on the right. Strain genotypes are listed across the top. There are eight FspI sites in the virB operon, including one in the virB4 gene and one in the virB10 gene, whose deletion results in larger hybridizing FspI fragments in the virB4 and virB10 mutants.