[Protein modification system in dormant cells].

Dormancy in an organism is an adaptive response to environmental stress. The initiation, maintenance, and breaking of dormancy are adaptations to environmental signals. In active cells, an environmental response is genetically controlled general phenomenon. However, no such system is available in dormant cells, in which almost all gene expression is repressed. Bacterial spores are dormant and highly resistant to many environmental stresses. I analyzed the protein profile of Bacillus subtilis spores by a combination of SDS-PAGE and LC-MS/MS to reveal protein modification in dormant cells. I found that protein modification was mediated by spore built-in enzymes YabG (a protease) and Tgl (a transglutaminase) in the spores of B. subtilis. The rearrangement of spore coat proteins caused by the activities of these built-in enzymes proceeded independently of gene expression or de novo protein synthesis in dormant cells. The results suggest that some built-in enzymes are activated under certain conditions and thereafter become involved in the modification of proteins and other cellular materials in dormant cells. I propose the idea that "Active" adaptation in active cells is dependent on gene expression, and that "Quiet" adaptation in dormant cells is dependent on the activity of some built-in enzymes independently of gene expression or de novo protein synthesis. Other enzymes are involved in restoration of dormancy in response to signals such as the nutrition.