RNA POLYMERASE IN VEGETATIVE CELLS OF BACILLUS SUBTILIS

III. ACCUMULATION OF RPASE L2 AFTER RIFAMPICIN TREATMENT INTRODUCED AT A SUBLETHAL CONCENTRATION

Abstract

When exponentially growing cells of Bacillus subtilis are exposed to sublethal concentration (0.1μg/ml) of rifampicin, they show an immediate decrease in the rate of RNA synthesis in vivo, followed by a latent period for 60min, and then a rapid recovery to the original level in 150 min. Cell growth and the viable cell count remained stationary for 90min and then began to increase at a much slower rate. RNA polymerase activity, extracted and assayed in vitro, followed the same pattern as RNA synthesis in vivo. The rifampicin-resistant fraction of the RNA-synthesizing activity, and the amount of β^γ subunit, a component of RNA polymerase (RPase) L2, increased with time after incubation in the presence of rifampicin. These results suggested that RPase L2, being a minor rifampicin-resistant fraction of RNA polymerases in normal state, increased several times in rifampicin-treated cultures, so as to make the cells phenotypically resistant to rifampicin.