A Novel Bi-Directional Channel for Nutrient Uptake across Mycobacterial Outer Envelope

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• Nutrient transport across cell membranes is well-studied, but less is known about transport through the complex mycobacterial outer envelope.
• The TiME (transporter in the mycobacterial envelope) protein secretion tube is a key structure in the mycobacterial outer envelope.

Purpose of the Study:

• To investigate the function of the TiME protein secretion tube in nutrient transport and survival of *Mycolicibacterium smegmatis*.
• To analyze the protein composition and transcriptome of the mycobacterial surface envelope in relation to TiME function.

Main Methods:

• Transcriptome analysis and proteomic profiling of *Mycolicibacterium smegmatis*.
• Gene deletion studies (*time* gene knockout).
• Nutrient uptake experiments using monosaccharides and amino acids.
• Bacterial growth assays under antibiotic stress and acidic pH conditions.

Main Results:

• Deletion of the *time* gene induced increased expression of transporters and porins in *Mycolicibacterium smegmatis*.
• TiME protein is essential for nutrient utilization, including growth on monosaccharides and amino acids.
• Loss of TiME function increased bacterial sensitivity to anti-tuberculosis drugs and impaired growth at acidic pH.

Conclusions:

• TiME protein secretion tubes are vital for nutrient acquisition and survival in challenging environments for mycobacteria.
• TiME facilitates bidirectional transport across the mycobacterial outer envelope, supporting both protein secretion and nutrient uptake.
• TiME plays a significant role in the survival of *M. smegmatis* in antibiotic-containing and acidic conditions, relevant to *Mycobacterium tuberculosis*.