A simple and efficient protoplast regeneration and PEG-induced transfo
rmation procedure was developed for Bacillus licheniformis. The protop
last stabilizing osmoticum was 0.5 M sucrose in the regenerating media
, and the restoration of cell wall was carried out at pH 8.4. The mean
frequency of regeneration was 83%. The transformation efficiency was
studied with four different strains and five plasmids, and ranged from
3.5 x 10(5) to 7.2 x 10(6) transformants per mu g plasmid DNA dependi
ng on the plasmid, and on the donor and recipient strains used. Endonu
clease digested and ligated plasmid DNA could also be used to transfor
m the protoplasts, but at a lower frequency.