Mechanosensation in bacteria involves transducing membrane stress into an electrochemical response. In Escherichia coli and other bacteria, this function is carried out by a number of proteins including MscL, the mechanosensitive channel of large conductance. MscL is the best characterized of all mechanosensitive channels. It has been the subject of numerous structural and functional investigations. The explosion in experimental data on MscL recently culminated in the solution of the three-dimensional structure of the MscL homologue from Mycobacterium tuberculosis. In this review, much of these data are united and interpreted in terms of the newly published M. tuberculosis MscL crystal structure.