Transformation of Clostridium perfringens L forms with shuttle plasmid DNA.

L-form (L-phase) cultures of Clostridium perfringens were tested for their transformability with plasmid DNA. Three L-form strains were transformable, but one, strain L-13, was superior to the others. This strain was easily and reproducibly transformed with previously described shuttle vectors which were derived from either C. perfringens or Escherichia coli. Strain L-13 was transformable by a variety of methods, and a new micromethod worked well under both aerobic and anaerobic conditions. The maximal number of transformants was attained after strain L-13 was exposed for 4 h to the transforming DNA and polyethylene glycol. Viable counts determined in tubes of semisolid brain heart infusion medium containing 10% sucrose, with or without 2 micrograms of tetracycline per ml, showed a transformation rate of 3.9 X 10(-5) (transformants per viable cells).