Mycobacterium tuberculosis is a facultative intracellular pathogen and the ability of this bacterium to survive and to grow inside macrophages is central to as 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 beta-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 (C) 2010 Elsevier Inc All rights reserved