Effects of CwlM on autolysis and biofilm formation in Mycobacterium tuberculosis and Mycobacterium smegmatis

Abstract

Tuberculosis is a highly infectious disease and of high incidence in low-income countries that is caused by Mycobacterium tuberculosis (M. tuberculosis). M. tuberculosis can form biofilms in vitro and in vivo, and the cells in the biofilm can survive at high concentrations of antibiotics. CwlM is a peptidoglycan hydrolase (amidase) and can hydrolyze bacterial cell walls, and the effects of CwlM on autolysis and biofilms is worthy of in-depth study. In this study, we successfully constructed an in vitro biofilm model of M. tuberculosis and Mycobacterium smegmatis (M. smegmatis). Reverse transcription followed by real-time quantitative PCR (qPCR) revealed that the expression of cwlM in M. tuberculosis and M. smegmatis was significantly up-regulated during the middle stage of biofilm formation. Treatment with recombinant CwlM enhanced the autolytic ability of M. tuberculosis and M. smegmatis and reduced the formation of their biofilms. As M. smegmatis is a model bacterium of M. tuberculosis, we built the M. smegmatis cwlM-deletion strain MSΔ6935, whose autolytic ability, biofilm production, and eDNA and eRNA content were determined to be lower than those of its parental strain. In conclusion, the cwlM gene plays a key regulatory role in biofilm formation in M. tuberculosis and M. smegmatis. This study provided a theoretical basis for using peptidoglycan hydrolase as a target for the inhibition of biofilms.