Transfer of the broad-host-range IncQ plasmid RSF1010 and other plasmid vectors to the gram-positive methylotroph Brevibacterium methylicum by electrotransformation.

Gram-positive facultative methylotrophic coryneform bacterium Brevibacterium methylicum was efficiently transformed with various plasmids using electroporation of intact cells. In addition to the plasmid vectors pEC71 and pZ6-1 constructed on the basis of cryptic plasmids from coryneform bacteria, broad-host-range plasmids pLS5 (derivative of plasmid pMV158 from Streptococcus agalactiae) and RSF1010 belonging to the incompatibility group IncQ from Gram-negative bacteria were found to be present as autonomous structurally unchanged DNA molecules in B. methylicum transformants. With the exception of pZ6-1, all these plasmids were stably maintained in B. methylicum cells grown under non-selective conditions. When plasmid DNAs isolated from B. methylicum were used, the highest efficiency of transformation (10(5) transformants/micrograms DNA) was achieved.

Genetic transfers in Brevibacterium sp.

A positive genetic transfer by protoplast fusion was obtained in auxotrophic mutants Brevibacterium sp. M27 his and Brevibacterium sp. M27 arg. Transformation and protoplast fusion with liposomes (as genetic transfers in intact cells and their protoplasts by both the chromosomal and plasmid DNA) did not lead to transfer of the markers followed.

Non-transformable mutants of Bacillus subtilis defective in the penetration of DNA into the cell.

Four non-transformable mutants of Bacillus subtilis 168 defective in the penetration of DNA into the recipient cell were isolated. All mutants were fully non-transformable with mutation in genes influencing irreversible binding of the donor DNA by the recipient cell.