The Influence of Mycobacterium tuberculosis Sigma Factors on the Promotion Efficiency of ptpAt Promoter in Mycobacterium smegmatis

It was found in a previous study that Mycobacterium tuberculosis protein tyrosine phosphatase ptpAt promoter is a highly active promoter in slow-growing species of mycobacteria, such as M. tuberculosis and M. bovis BCG, but inert in fast-growing mycobacterial species, such as M. smegmatis. This difference is presumed to be due to the differences between sigma factors systems of slow-growing pathogenic mycobacteria and the fast-growing saprophyte M. smegmatis. Therefore, we constructed a series of plasmids, named pOLYG-13x, which can express various M. tuberculosis sigma factors and also contain a PptpAt-gfp reporter gene construct. By inducing different sigma factor genes of M. tuberculosis in M. smegmatis, we were able to explore the influences of various sigma factors on the expression efficiency of the ptpAt promoter. The result show that of the 10 sigma factors evaluated, only sigF and sigL were able to weakly drive the ptpAt promoter in M. smegmatis and other sigma factors were unable to drive the promoter.