The blasticidin S resistance gene (bsr) selectable in a single copy state in the Bacillus subtilis chromosome.

The blasticidin S resistance gene (bsr), originally isolated from Bacillus cereus, was studied in Bacillus subtilis. It was found that a 617 bp fragment including the intact bsr gene and its 5' flanking region could confer BS resistance on B. subtilis when integrated in its chromosome, even in a single copy state. The construction of a bsr gene cassette and its practical application as a novel selection marker for B. subtilis are reported.