Organic agriculture and the trend of reducing usage of chemical pesticides require the development of biological pest-control methods. They include using natural pathogens of insects, like Bacillus thuringiensis. It is Gram-positive bacterium, which produces a great variety of different toxins of proteinaceous and non-proteinaceous nature. Among them, highly specific crystal-forming Cry-toxins are accumulated upon transition from the stage of vegetative cells to spores. The set of Cry-toxins produced by each strain of B. thuringiensis, is remarkably diverse and determines the host-specificity of the strain. The Cry-toxins’ genes are harbored on the different plasmids, which also contain genes encoding proteins involved in the process of sporulation. The strains of B. thuringiensis differ in the number of plasmids in their genomes, but the strain specificity of proteins produced in spores and vegetative cells at proteomic level remains poorly studied. In this study we used HPLC-Orbitrap-MS proteomics to quantitively compare the production of proteins at two stages, vegetative cells and spores, in three different B. thuringiensis serovars, var. thuringiensis, var. darmstadiensis and var. israelensis. Also, we compared B. thuringiensis var. israelensis with one strain of the same serovar, which lacked the ability to produce Cry-toxins. As expected, Cry-toxins were identified at spore stage in all strains except the one, which could not produce them. We also identified a set of proteins differentially expressed at the stage of spores including spore coat proteins, flotillin-like proteins and exosporium proteins. These proteins participate in the cell differentiation and exosporium attachment to the spore. Taking together, the data obtained in this study revealed the differences between proteomes of B. thuringiensis strains at the stages of vegetative cells and spores and have shown the similar patterns in the protein production across different serovars. This work was supported by the Russian Foundation for Basic Research (Grant No 20-316-70020).
