"Marker augmentation" phenomenon in the plasmid transformation and transduction of Bacillus subtilis

Transformation of Bacillus subtilis cells carrying pUB110 plasmid by DNA of homologous plasmid pBD12 results in the significant increase in the number of plasmid transformants. This phenomenon named "augmentation" was not observed when instead of intact cells, regenerating protoplasts were used, or if pBD12 DNA was introduced into the cells via transduction.