ACTINOMYCIN RESISTANCE IN BACILLUS SUBTILIS.

The incorporation of uracil-C(14), a precursor of cellular RNA, into whole cells of the sensitive parent strain Bacillus subtilis No. 6051 is completely inhibited by actinomycin D, whereas only partial inhibition of uracil-(14) incorporation occurs with actinomycin-resistant intact cells of B. subtilis strain II 15. Incorporation of uracil-C(14) into protoplasts of the resistant strain of B. subtilis is completely inhibited. The sensitivity of resistant-cell protoplasts to drug effect clearly supports the conclusion that actinomycin penetration is altered in resistant intact whole cells. Since other experiments have shown that the antibiotic is not broken down in the presence of resistant cells, resistance is considered to result from a change in cell permeability.