Plasmids designed to alter the antibiotic resistance expressed by insertion mutations in Bacillus subtilis, through in vivo recombination.

Numerous insertion mutations conferring resistance to antibiotics are available in Bacillus subtilis. However, many of them have been constructed in vitro by inserting genes from the Staphylococcus aureus plasmids, pC194 or pE194, conferring resistance to chloramphenicol (Cm) or erythromycin (Er). Others are insertions of the Enterococcus faecalis Tn917 transposon conferring resistance to Er. This paucity of resistance markers has been limiting the possibilities of constructing and studying mutants carrying two or more of these mutations in the past. We constructed plasmids which can be used to change the antibiotic resistance expressed by preexisting chromosomal insertions, through transformation and homologous recombination. These vectors replace the pre-existing resistance to Cm or Er with new resistances to neomycin (Nm), phleomycin (Pm), spectinomycin (Sp) or tetracycline (Tc).