Proteomics characterization of novel spore proteins of Bacillus subtilis.

The spores of Bacillus subtilis have characteristic properties and consist of complex structures including various types of proteins. To perform comprehensive analysis of the protein composition of the spores, the proteins extracted from the spore were analysed by a combination of one-dimensional PAGE and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) using Turboquest SEQUEST software interfaced with the DNA sequence database of B. subtilis. A total of 154 proteins were identified, and 69 of them were novel. The remaining 85 proteins have been previously reported as sporulation-specific proteins or as proteins that are synthesized in vegetative cells. The expression pattern of each gene deduced to encode novel spore proteins was analysed using a series of strains carrying a lacZ reporter gene. The results revealed that the expression of 26 genes was dependent on sporulation-specific sigma factors, namely sigma(F), sigma(E), sigma(G) and sigma(K). In this study, it is demonstrated that the combination of the techniques of SDS-PAGE and LC-MS/MS, with the mutant library of B. subtilis, is an effective tool for the analysis of complicated cellular structures.