Mutation of Bacillus subtilis causing hyperproduction of alpha-amylase and protease, and its synergistic effect.

Mutants that had a genetic lesion increasing the production of alpha-amylase and protease simultaneously were isolated from a transformable strain of Bacillus subtilis Marburg by N-methyl-N'-nitro-N-nitrosoguanidine treatment. These mutants produced two to three times more alpha-amylase and five to 16 times more protease than their parent and were tentatively referred to as AP mutants. As this mutation seems to have occurred at a single gene of the bacterial chromosome and was not located near the alpha-amylase structural gene, the gene was designated as "pap." When pap- and amyR2 (an alpha amylase regulator gene) or pap- and ProH coexisted in the same cell, synergistic effects of the two genetic characters were observed on the alpha-amylase and protease production, respectively. Upon introduction of the pap mutation, the following phenotypic changes were observed in addition to changes in alpha-amylase and protease productivity. (i) Mutants lost the character of competence for the transformation. (ii) When cells were cultured at 30 C for 30 h, mutant cells became filament owing to the formation of chains of cells. (iii) Autolysis of cells was decreased in the mutants. When pap- was transferred to the wild strain by deoxyribonucleic acid-mediated transformation, the transformants showed all these phenotypic alterations simultaneously.