Genetic and physical organization of the cloned gyrA and gyrB genes of Bacillus subtilis.

An 8-kilobase fragment already known to contain the gyrA gene of Bacillus subtilis was shown to encode the gyrB gene as well. Plasmids containing this fragment can rescue both B. subtilis gyrA and gyrB mutants and complement Escherichia coli gyrA mutants. Deletion analysis has indicated the gene locations on the cloned fragment. Under low-stringency conditions the cloned E. coli gyrA and gyrB genes each hybridized to the appropriate subfragments, confirming the assignment of the gene locations on the cloned DNA. In E. coli maxicells, proteins of 67,000 (gyrA) and 77,000 (gyrB) Mr were synthesized. Analysis of proteins encoded by various subfragments indicated the direction of transcription. Although the gyrA and gyrB genes are located adjacent to each other on the chromosome, they may be transcribed independently since expression of gyrA protein is not dependent upon the gyrB gene in maxicells.