Characterization of different types of radiation- and pressure-induced DNA damage in Bacillus subtilis spores and their global transcriptional response during spore germination

Abstract

In general, the individual transcriptional responses of B. subtilis 168 spores to treatments by either UV-C, UV-A, X-rays, accelerated heavy ions or extreme desiccation showed certain similarities. Those corresponding responses included the induction of systems involved in DNA modification (i.e. repair, recombination, replication and packaging), in nucleotide replacement (i.e. binding, synthesis and nucleotide acid metabolism) as well as in adaptation (i.e. stress response). The similar – partly identical - responses of spores to various DNA damaging stresses point to the existence of a general “built-in”-transcriptional germination program in spores with key transcriptional events as checkpoints for ensuring DNA restoration and integrity. “Forward” spore protection mechanisms established during sporulation, such as Ca-DPA-complex, dehydration, A-DNA conformation, spore coat layers, spore core minerals, DNA binding by SASPs and the synthesis of the DNA repair systems SP lyase and NHEJ, interact with “backward” spore repair mechanisms activated or induced during germination and outgrowth, such as the reactivation of ATP- and macromoleculesbiosynthesis, (universal pathways or spore specific), active DNA repair of accumulated damage and de novo nucleotide/nucleic acid synthesis. This concerted interaction of “forward” spore protection and “backward” spore repair may constitute the major strategy of spores to maintain their high resistance towards a variety of hazardous stresses when attacked in the spore state. The identification of transcriptional and biochemical changes, elaborated in this work, has contributed substantial facets to this understanding.