High frequency conjugative mobilization accomplished by a natural Bacillus subtilis strain carrying a large plasmid

Conjugative properties of the strain Bacillus subtilis carrying a large plasmid approximately 95 kb in size and isolated in Belarus from forest soil were described. The staphylococcal. plasmid pUB110 that had previously been introduced into this strain was transferred to recipient cells of the Bacillus subtilis 168 strain with a frequency of approximately 10(-2). The transfer occurred with approximately the same frequency both upon donor and recipient cell contact on the surface of membranes and in a liquid medium. The latter fact makes this system suitable as a model for studying conjugative mobilization in bacilli. A large plasmid cannot be transferred to recipients. An optimal temperature for conjugation of donor and recipient cells was 37 degreesC, but conjugation also proceeded at lower temperatures, up to 21 degreesC.