Chloramphenicol induces translation of the mRNA for a chloramphenicol-resistance gene in Bacillus subtilis.

cat-86 is a plasmid gene specifying chloramphenicol-inducible chloramphenicol acetyltransferase activity in Bacillus subtilis. Inducibility has been suggested to result primarily from activation of the translation of cat-86 mRNA by subinhibitory levels of chloramphenicol. To directly test the involvement of transcription in cat-86 induction, the gene was transcriptionally activated with a strong promoter, resulting in the synthesis of relatively high levels of cat-86 mRNA in uninduced cells. When RNA synthesis was blocked with rifampin (100 micrograms/ml), de novo inducibility of cat-86 by chloramphenicol could be demonstrated for more than 30 min. These results indicate that concurrent transcription is not essential for cat-86 induction. Accordingly, cat-86 is one of only a few inducible bacterial genes in which the primary form of regulation is at the translational level. This form of regulation may apply to other cat genes of Gram-positive origin whose expression is also inducible by chloramphenicol.