Modulation of an apparent mRNA pool for extracellular protease in Bacillus amyloliquefaciens.

Late-log-phase cells of Bacillus amyloliquefaciens have the unusual capacity to produce extracellular protease for over 60 min in the presence of rifampin or actinomycin D at levels which strongly inhibit incorporation of amino acids into cellular protein. If cells are incubated in the presence of high levels of amino acids for 75 min this capacity is exhausted, but it is retained if the incubation is carried out in low levels of amino acids. Transfer of exhausted cells from high to low concentrations of amino acids results in a progressive recovery of the capacity for rifampin-actinomycin-insensitive protease production. The results seem best explained on the basis of the accumulation of a reserve pool of mRNA for extracellular protease. Measurement of the apparent mRNA pool size over 12 h shows a cyclical rise and fall, and these changes correlate with a periodic variation of the rate of protease production. A working hypothesis is presented to account for these observations in terms of a novel control situation over protease mRNA transcription.