Improved transformation system of Bacillus subtilis competent cells using polymerase chain reaction DNA fragments as donor DNA

To enhance the transformation efficiency of Bacillus subtilis Marburg 168 using PCR DNA fragments, we optimized the competent cell preparation by adding Mn2+ to the competence medium. This Mn2+ addition promoted both cell growth and increased transformation frequency. Moreover, we determined the necessary length of the homologous sequence on each end to achieve practically sufficient transformation through double crossover recombination.