Plasmid transformation in Bacillus subtilis NB22, an antifungal-antibiotic iturin producer

A transformation system with plasmids was developed for Bacillus subtilis NB22, an antibiotic iturin producing strain. Treatment of B. subtilis NB22 with 4 M KCl was effective for the induction of competence, followed by uptake of plasmid DNA in the presence of polyethylene glycol. The efficiency of transformation of this bacterium with pC194 and pUB110 was 4.1 × 103 and 1.5 × 103 transformants per μg DNA, respectively and the transformation frequency was 3.3 × 10−3 and 7.2 × 10−4, transformants per viable cell, respectively. This method was much faster and three orders of magnitude more efficient in transformation efficiency than protoplast transformation methods.