FIG. 2.

Southern blot analysis of chimera strains. All blots are BamHI digests of chimera chromosomal DNA. (A) ISPG4 probe of chimeras to identify 33277- or W83-derived strains. (B) ISPG1 probe of chimera DNA. The arrow indicates the additional ISPG1 band acquired by the W83-derived chimera. (C) Location of tetQ and ermF markers in chimera genomes. The arrow indicates the ermF band in chimera 9, which shows a unique restriction profile compared to the donating parent, W83Em. (D) A PG0653 probe of the same blot as that in panel C. The PG0653 band in chimera 9 (indicated with an arrow) has the same BamHI restriction sites as the 33277Tc strain, with an additional 1.1 kb due to the presence of the ermF cassette from the donating parent, W83Em. (E) Homologous DNA recombination events that result in chimeras 2, 4, and 9. These chimeras result from the W83Em donation of ermF to 33277Tc. Bold lines represent the donated DNA, and thin lines represent the chromosomal DNA in the recipient. “B” indicates BamHI restriction sites. The bold X represents putative regions of homologous recombination.