Discrimination of competent Bacillus subtilis with respect to ribonucleic acids

Abstract

A study has been made of the affinity of double-stranded helical RNA for DNA receptors in competent Bacillus subtilis. In competition experiments, using homologous and heterologous DNA samples which had been sheared to molecular weights comparable to that of the RNA (about 2 x 10(6)), and which still exhibited appreciable competition in DNA uptake experiments, the replicative form of phage f2 RNA showed no evidence of affinity for receptor sites. A second double-stranded RNA preperation from a widely different source, a mycophage of Penicillium chrysogenum, behaved similarly to the f2 RNA. Transfer RNA and 23S ribosomal RNA, which reduce transformation frequencies in pneumococcus, did not compete for B. subtilis receptors. Lack of competition was not due to enzymatic degradation of the RNA, since the latter was recovered intact following exposure to competent cells. Under conditions where homologous native DNA undergoes normal uptake, there was virtually no uptake of native double-stranded RNA. The results are examined in the light of reports on transformation by RNA and DNA-RNA hybrids, and also in relation to the characterization of the specificity of cell-nucleic acid interactions.