BIOMEDICAL JOURNAL OF PIROGOV RNRMU (MOSCOW, RUSSIA)
CRISPR-Сas systems of Mуcоbacterium tuberculosis: the structure, transformation in different lineages in the process of evolution and a possible role in the formation of virulence and drug resistance
CRISPR-Сas systems are widespread in bacteria and archaea. They provide adaptive immunity against bacterial phages and plasmids and exert a few important functions like regulation of gene expression, DNA repair or virulence formation. We have analyzed the CRISPR-Cas systems of 7 Mусоbacterium tuberculosis lineages with fully sequenced genomes, namely Beijing, B0/W-148, EAI, Haarlem, Ural, LAM, and S. The CRISPR-Cas systems present in the analyzed genomes belong to type III-A. M. tuberculosis lineages differ in their CRISPR-Cas structure; in the Beijing lineage a part of the system is reduced. We have conducted a search for the functionally related partners and compensatory mechanisms of cas-genes using a method of phylogenetic profiling. The obtained phylogenetic profiles show that some genes have undergone similar evolutionary events. The reduction of the system’s part in the Beijing lineage was accompanied by at least two evolutionary losses and one acquisition of genome regions. Exploration of alternative CRISPR-Cas functions in M. tuberculosis and their possible associations with other gene systems remains an exciting challenge.
Keywords: CRISPR-Cas systems, virulence, Beijing lineage, phylogenetic profiling, Mуcоbacterium tuberculosis, CRISPR-Сas