Bacterial secretion systems are specialized protein complexes and pathways that allow bacterial pathogens to secrete proteins across their cell membranes and, ultimately, to host cells. These effector proteins are important virulence factors, which allow the pathogen to survive inside of the host. There are many different kinds of specific secretion systems, and M. tuberculosis has an Snm (secretion in mycobacteria) protein secretion system. Although the Snm secretion system is a key in determining M. tuberculosis virulence, all mycobacteria have genes encoding the components of this system. This area of the genome is referred to as the RD1 locus. M. smegmatis is commonly used to study Snm secretion because of its genetic similarities  and analogous function to M. tuberculosis, as well as ease of growing in the lab. One example of how this can be applied in research is the identification of gene products required for Snm secretion. By knocking out genes in the RD1 locus of M. smegmatis and testing efficiency of Snm secretion before and after gene knockout, specific genes can be identified as necessary for Snm secretion. These findings can be applied to the Snm secretion system of M. tuberculosis.
