Figure 1. Accumulation of storage lipids by Mtb under multiple-stress in vitro.

Mtb was subjected to a combination of four stresses - high CO₂, low O₂, acidic pH and nutrient starvation. Total lipids were extracted at 0, 3, 9 and 18 days and resolved on silica-TLC using hexane-diethyl ether-formic acid (90∶10∶1, v/v/v). Lipids were visualized by charring after spraying with dichromate-sulfuric acid and quantified by densitometry using Alpha Innotech Gel documentation system and AlphaImager 2200 software (Alpha Innotech, USA). TG, triglycerides; WE, wax esters.