Abstract:[Objective] To reveal the function of PE_PGRS15 from Mycobacterium tuberculosis. [Methods] A recombinant Mycolicibacterium smegmatis strain heterologously expressing PE_PGRS15 (MS-PE_PGRS15) was generated. The colony morphology, cell surface morphology, and envelope structure were observed by a plating method, a scanning electron microscope, and a transmission electron microscope, respectively. The localization of PE_PGRS15 was detected by the cell fractionation assay. The resistance of the recombinant strain to environmental stresses and antibiotics was measured by the killing curve method and micro-broth dilution method. The permeability and fatty acid profile of the cell wall of the recombinant strain were determined by dye uptake assay and gas chromatography-mass spectrometry, respectively. The functions of different domains of PE_PGRS15 were analyzed by protein truncation and fusion experiments. [Results] PE_PGRS15 was located on the cell envelope of MS-PE_PGRS15. MS-PE_PGRS15 showed altered colony morphology, envelope structure, and cell wall fatty acid profile, with noticeable increase in resistance to multiple environmental stresses and antibiotics. The dye uptake experiments with ethidium bromide and Nile red suggested that the cell wall of MS-PE_PGRS15 was more impermeable than that of the control strain. The PGRS domain of PE_PGRS15 affected mycobacterial cell wall permeability and stress resistance, while the PE domain was involved in the transport of the protein to the cell surface. [Conclusion] PE_PGRS15 was present in the cell wall fraction of MS-PE_PGRS15 and influenced cell wall permeability and colony morphology, ultimately enhancing the resistance of recombinant M. smegmatis to stresses.
