RECA-INDEPENDENT INDUCTION OF THE NEW PLA SMID PAS1 AFTER THE INTRODUCTION OF FRAGMENTS OF CRYPTIC PLASMID P1414 IN BACILLUS-SUBTILIS-168 CELLS

Bacillus subtilis 168 was transformed with fragments from the minirepl icon of the cryptic plasmid p1414; these fragments were ligated into t he cat gene of plasmid pC194. As a result, the 4.6 kb plasmid pAS1 app eared with a low frequency. The plasmid was homologous to the chromoso mal DNA of B. subtilis 168, but had no homology with p1414. Plasmid pA S1 had extensive homology (3.2 kb) with plasmid pUB110 and its restric tion map in this region of homology correlated well with the restricti on map of pUB110. Plasmid pAS1 occurred both in rec+ and recA- cells. We suppose that pAS1 was generated because of the illegitimate recombi nation between p1414 and the replicon pUB110 incorporated in the chrom osome of B. subtilis 168, and the resulting substitution of marker Km( R) of pUB110 for marker Cm(R) of pC194.