Deletion of PimE mannosyltransferase results in increased copper sensitivity in Mycobacterium smegmatis

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• Mycobacterium tuberculosis possesses a unique cell envelope crucial for pathogenesis.
• Phosphatidylinositol (PI)-anchored glycolipids like PIMs are vital cell envelope components in mycobacteria.
• The precise roles of these glycolipids in maintaining cell envelope integrity remain incompletely understood.

Purpose of the Study:

• To investigate the function of the mannosyltransferase PimE in Mycobacterium smegmatis.
• To determine the impact of pimE gene deletion on cell envelope integrity and growth under stress conditions.

Main Methods:

• Generation and characterization of a pimE deletion mutant (ΔpimE) in Mycobacterium smegmatis.
• Comparative growth analysis of wild-type and ΔpimE strains on different agar media (Middlebrook 7H10 vs. M63).
• Assessment of ΔpimE sensitivity to copper and various antibiotics.

Main Results:

• The ΔpimE mutant exhibited a small colony phenotype on Middlebrook 7H10 agar, which was alleviated on M63 agar.
• Copper present in Middlebrook 7H10 was identified as the cause of growth retardation in the ΔpimE mutant.
• The ΔpimE mutant displayed increased sensitivity to several antibiotics, independent of copper presence.

Conclusions:

• PimE is essential for protecting the mycobacterial cell envelope against toxic compounds like copper.
• Deletion of the pimE gene compromises cell envelope integrity, leading to vulnerability to environmental stressors and antibiotics.
• These findings highlight the importance of specific mannosyltransferases in maintaining mycobacterial cell envelope stability.