[Sigma factor F regulates Mycobacterium smegmatis hydrogen peroxide resistance]

A sigma factor is an important component of RNA polymerase complex and is essential for initiation of RNA synthesis. The sigma factors fall into 2 categories: primary sigma factor is essential for bacterial growth and the alterative sigma factor is activated under different environmental conditions. Sigma F (SigF) is one of the sigma factors of Mycobacterium tuberculosis, affecting its virulence and pathogenesis. In contrast, the ortholog of the non-virulent, fast growing strain Mycobacterium smegmatis has been suggested without similar physiology roles. Here, we studied the functions of M. smegmatis SigF.

sigF knockout Mycobacterium smegmatis strain was constructed by specialized transduction. The wild type, knockout and complementary stains were challenged by oxidative stress and antibiotics.

The knockout sigF stain was susceptible oxidative stress, compared to wild type. Furthermore, there was no defect in resistance to antibiotics including isoniazid between the knockout sigF strain and wild type strain. In addition, SigF is required for carotenoid pigment production in M. smegmatis.

Our data suggested that SigF is important to detoxify the reactive oxygen species, probably through photo-oxidative stress response pathway, which is independent on the pathway that is required for the isoniazid activation.