Stress Responses in Mycobacterium
Richard W. Stokes
from: Stress Response in Microbiology (Edited by: Jose M. Requena). Caister Academic Press, U.K. (2012)
There are many species of mycobacteria, some of which are pathogens of man. Mycobacterium tuberculosis, the etiological agent of tuberculosis, is a major pathogen of man with about one third of the world's population being infected. It resides within host macrophages where it can survive in a dormant state for the lifetime of the host with about 10% of all infections resulting in disease. This environment results in the bacteria being exposed to numerous stresses including nutrient deprivation, reduced oxygen availability, exposure to pH changes and exposure to the antimicrobial activities of the host's cell-mediated immune response. The bacterium responds with its own defense mechanisms that include the increased expression of stress proteins (also called heat shock proteins). This review describes the regulation and function of the major stress proteins within mycobacteria such as the GroEL, GroES and DnaK homologues along with hspX (alpha-crystallin) and others. The multiple copies of cpn60 (GroEL homologue) that are found within mycobacteria are discussed along with their putative roles as chaperonins but also as "moonlighting" proteins with roles in immunomodulation and receptor/ligand interactions that facilitate the pathogenesis of M. tuberculosis read more ...