The σ factors of Mycobacterium tuberculosis

Mycobacterium tuberculosis is a remarkable pathogen capable of adapting and surviving in various harsh conditions. Correct gene expression regulation is essential for the success of this process. The reversible association of different sigma factors is a common mechanism for reprogramming bacterial RNA polymerase and modulating the transcription of numerous genes. Thirteen putative sigma factors are encoded in the M. tuberculosis genome, several being important for virulence. Here, we analyse the latest information available on mycobacterial sigma factors and discuss their roles in the physiology and virulence of M. tuberculosis.