Abstract
Mycobacterium tuberculosis is a facultative intracellular pathogen, and the ability of this bacterium to survive and to grow inside macrophages is central to its virulence. Multiple strategies are employed by
M. tuberculosis to ensure survival in macrophages, including secretion of several proteins, which are good candidates to be virulence factors, drug targets for disease intervention, and vaccine antigens. However, some
M. tuberculosis secreted proteins do not appear to play any role in the growth or survival of the bacterium in its mammalian host. Among these proteins are three putative cellulose-targeting proteins encoded by the genes
Rv0062, Rv1090, and
Rv1987. It has been previously shown that
Rv0062 encodes an active cellulase. Here we report that
Rv1090 and
Rv1987 also encode functional proteins. Rv1090 is able to hydrolyze barley β-glucan while Rv1987 displays cellulose-binding activity on filter paper and on microcrystalline cellulose (Avicel). Collectively, these observations point toward a unique unknown relationship between
M. tuberculosis and a cellulose-containing host. We hypothesize that amoeba could be such hosts.