Isolation and characterization of Bacillus megaterium mutants containing decreased levels of spore protease.

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Abstract
A proteolytic activity present in spores of B. megaterium was previously implicated in the initiation of hydrolysis of the A, B, and C proteins which are degraded during spore germination. Four mutants of B. megaterium containing 20-30% of the normal level of spore proteolytic activity were isolated. Partial purification of the protease from wild-type spores by a revised procedure resulted in the resolution of spore protease activity on the A, B, and C proteins into 2 peaks: a major one (protease II) and a minor one (protease I). The protease mutants tested lacked active protease II. All of the mutants exhibited a decreased rate of degradation of the A, B, and C proteins during spore germination at 30.degree. C, but degradation of the proteins did occur. Degradation of the A, B, and C proteins during germination of the mutant spores was decreased neither by blockade of ATP production nor by germination at 44.degree. C. Initiation of spore germination was normal in all 4 mutants, and all 4 mutants went through outgrowth, grew and sporulated normally in rich medium. Similarly, outgrowth of spores of 2 of the 4 mutants was normal in minimal medium at 30.degree. C. In the 2 mutants studied, the kinetics of loss of spore heat resistance and spore UV light resistance during germination were identical to those of wild-type spores. This indicates that the A, B, and C proteins alone are not sufficient to account for the heat or UV light resistance of the dormant spore.

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