Many pathogenic bacteria, including M. tuberculosis, secrete effector proteins using Sec-independent secretion pathways to manipulate host-cells in order to grow and persist during infection. In M. tuberculosis, the Snm (secretion in mycobacteria) system is required for virulence and consists of three components required for the translocation of two known substrates. The current hypothesis is that the Snm pathway is a conserved system by which bacteria manipulate eukaryotic phagocytes. Because this novel secretion system is conserved in the non-pathogenic soil bacterium Mycobacterium smegmatis, further characterization of the Snm system using this mycobacterial species will be performed. Both genetic and biochemical approaches will be used to identify other substrates of the Snm secretion system and to determine a secretion signal common to these substrates. Mutants in components and in regulators of the Snm secretion system will also be identified genetically. Finally, the biological role of the Snm system in M. smegmatis will be explored through the development of an interaction model with the genetically tractable soil amoebae Dictyostelium discoideum and Acanthamoeba castellanii. ? ?
