Cellular Changes Accompanying the Transition from Minimal to Maximal Rate of Extracellular Enzyme Secretion by Bacillus amyloliquefaciens

S ummary . During exponential growth of Bacillus amyloliquefaciens in a maltose–L‐amino acids medium at 30°, cellular protein, RNA and DNA increased in parallel. After the exponential phase, extracellular protein, including α‐amylase, was secreted into the medium at a quarter of the maximum rate of total cellular protein synthesis. The free amino acid pool for protein and the ‘nucleotide’pool for RNA both increased fourfold during the transition to the post‐exponential phase to 4.0 and 1.6%, respectively, of the cellular dry weight. Subsequently, the nucleotide pool did not change significantly whilst the free amino acid pool was reduced to 2/3 of its maximum size. When post‐exponential phase, exoprotein‐secreting bacteria were transferred to fresh culture medium, growth was re‐established and there was a 4–5 fold reduction in nucleotide pool size accompanied by a loss of exoenzyme‐forming ability.