Growth Kinetics and Characterization of Mycobacterium Fortuitum Sense and Antisense Mutants of Sigma Factor Sigh

Abstract

Mycobacterium fortuitum is an important clinical pathogen causing localized abscesses, pulmonary disease and disseminated infections in humans. It is fast growing non tuberculous mycobacteria. It has worldwide distribution and found in natural and processed water, dirt and sewage. Among all the NTM, it is responsible for 67% of infections. Severity of infection is more in immunocompromised patient. Sigma factors play vital role in different stress responses as it regulates the expression of gene. Sigma factor H (sigH) plays central role in a network that regulates stress responses likely to be important in Mycobacterium tuberculosis pathogenesis. With an aim to study role of sigma factor H in regulation of stress response and pathogenesis of M. fortuitum, sense and antisense knockouts were constructed using pMV261 vector. Role of sigH was determined under different stress conditions by subjecting the sense and antisense mutants along with wild type M. fortuitum as control. sigH was involved in hypoxia-induced, acid-induced stress response, and other in-vitro stress conditions. We have found that sigH plays an important role during acidic stress at pH 4.5 and nutrient starvation whereas during other stress conditions such as heat stress at 50oC, oxidative stress and SDS stress, sigH may not have its role in M. fortuitum. Our study suggests that the overexpression as well as underexpression of sigH inhibits its own expression under invivo conditions, and the other genes responsible for the survival of M. fortuitum in mice model of infection.