Incorporation of the Whole Chromosomal DNA in Protoplast Lysates into Competent Cells of Bacillus subtilis

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Competent cells of Bacillus subtilis AC870 (purB, leuB, trpC, ald-1) were transformed to Ade⁺, Trp⁺, or Ade⁺ Trp⁺ with DNA in protoplast lysates of B. subtilis AC819 (hisH, tet-1, rpsL, smo-1). The contransfer ratio of purB to trpC was constant at 7-9% (Ade⁺ Trp⁺/Trp⁺) or 3% (Ade⁺ Trp⁺/Ade⁺) at protoplast concentrations of 2.7×10³∼2.7×10⁶ per ml. The whole chromosomal DNA must be certainly incorporated into competent cells from the following reasons; (1) purB is opposite to trpC on the chromosome, (2) 2.7×10³ protoplasts per ml is about 100 times lower than 3.2×10⁵ competent cells per ml, and (3) the cotransfer ratio is constant at all the concentrations. Similar results were obtained with the cotransfer ratio of purA to trpC. The transformation requires several Com proteins including ComK.