The Mycobacterium tuberculosis Sigma Factor σB Is Required for Full Response to Cell Envelope Stress and Hypoxia In Vitro, but It Is Dispensable for In Vivo Growth

The numerous sigma (σ) factors present in Mycobacterium tuberculosis are indicative of the adaptability of this pathogen to different environmental conditions. In this report, we describe the M. tuberculosis σB regulon and the phenotypes of an M. tuberculosis sigB mutant strain exposed to cell envelope stress, oxidative stress, and hypoxia. The sigB mutant was especially defective in survival under hypoxic conditions in vitro, but it was not attenuated for growth in THP-1 cells or during mouse and guinea pig infection.