Proteomic analysis of hydroxyl radical-induced resuscitation of hypoxia-induced dormant mycobacterial cells.

Background: The genus Mycobacterium has an ability to persist in hostile environments for years before its reactivation in favorable conditions. The major bottleneck in decades of mycobacterial research is a poor understanding of molecular mechanism which assists bacteria to attain dormancy and reactivation later.

Methods: In this study, hydroxyl radical was quantified in aerobically growing mycobacterial cells using 2-deoxy-D-ribose assay. Furthermore, extraneous addition of hydroxyl radical in Wayne's dormancy model induced reactivation of dormant cells. The whole proteome of all three samples, namely, aerobic, Wayne dormancy, and hydroxyl radical reactivated cells was isolated, trypsin digested, and peptides are quantitatively characterized by liquid chromatography-elevated energy mass spectrometry.

Results: This study reports the generation of highly reactive hydroxyl radical by Mycobacterium smegmatis during aerobic respiration. The hydroxyl radical levels can be managed by modulation of iron ions in the cellular pool. Proteomic characterization of resuscitation process highlights the increase in the level of ATPases, iron acquisition, redox response, changes in cell membrane dynamics, and cell wall hydrophobicity which is coupled with restoration of protein synthesis, carbohydrate, and lipid metabolism. In addition, two uncharacterized universal stress proteins MSMEG5245 and MSMEG3950 were uniquely identified in reactivated cells.

Conclusion: Overall, the 1-hydroxypyridine-2-thione-induced reactivation process is a controlled and stepwise exit from dormancy.