Broad Audience Title

Finding a treatment for drug resistant tuberculosis

Scientific Title

Mycobacterium smegmatis membrane dynamics in response to various stress conditions

By Samantha Giffen
Biomedicine/Biosystems
iCons Year 4
2016
Executive Summary 

Mycobacterium tuberculosis, a causative agent of tuberculosis, infects nearly one third of the world's population. The highly impermeable cell envelope of this pathogen represents an important barrier against host immune responses and antibiotic treatments. Regulation of cell envelope elongation under various stress conditions is likely critical, but the molecular mechanisms remain largely unknown. My research is focused on determining the membrane dynamics in Mycobacterium smegmatis in response to the inhibition of cell wall biosynthesis through the use of antibiotics and genetic disruption.

In M. tuberculosis as well as Mycobacterium smegmatis, a non-pathogenic model organism, cell envelope elongation is spatially restricted to the cell pole. Our studies suggest the presence of a membrane domain termed the PMf specifically enriched in the polar growth region, suggesting that the PMf is a biogenic membrane domain crucial for cell envelope biogenesis. Here, we tested if various stress conditions including nutrient depletion and antibiotic treatments affect the polar localization of the PMf.

To monitor the PMf, we chose two protein markers identified as PMf-associated proteomics: 1) GlfT2, a galactosyltransferase involved in arabinogalactan cell wall biosynthesis, and 2) Ppm1, a polyprenol-phosphate-mannose synthetase involved in lipomannana and lipoarabinomannan biosynthesis. Using mCherry-tagged GlfT2 and mNeonGreen-tagged Ppm1, we examined changes in the distributions of the PMf during growth under the microscope. Consistent with the role of the PMf in active cell envelope elongation, polar localization of the PMf became less pronounced in the stationary phase. Furthermore, incubation with a suboptimal concentration of cycloserine, a peptidoglycan biosynthesis inhibitor, resulted in the loss of the polar PMf enrichment. We are currently testing if other antibiotics for similar effects on PMf localization.

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