Regulation of Extracellular Protease Production in Bacillus cereus

Abstract

Both sporulation and protease production can be inhibited by growing Bacillus cereus T in a medium containing a high concentration of a mixture of amino acids. Mutants selected for the ability to sporulate in this inhibitory medium were found to produce high levels of protease in the normal and inhibitory media. Comparison of the mutant and wild-type enzymes by gel electrophoresis and heat inactivation suggested that they were identical. One of the mutants proved to be a purine-requiring auxotroph. Reversion to prototrophy resulted in the loss of the capacity to sporulate in the inhibitory medium and loss of the ability to produce large amounts of protease. Mutants capable of producing high levels of protease and of sporulating in the inhibitory medium were also found when selecting for a purine, pyrimidine, or lysine requirement or for the capacity to sporulate in the presence of a high concentration of glucose. Protease production could be considerably delayed in the purine auxotrophs or completely inhibited in the pyrimidine auxotrophs by growing the cells in a medium containing the inhibitory mixture of amino acids plus hypoxanthine for the former or a pyrimidine for the latter. The fact that a variety of metabolic alterations could lead to excessive protease production suggested that a common catabolic or biosynthetic intermediate was involved in the control of the production of this enzyme(s).