FIG. 4.

Menaquinone content of M. tuberculosis H37Rv cells in the RAD dormancy model. Cultures were terminated at the indicated time point (days). Day 0 corresponds to logarithmic aerobic growth. Harvested cells were extracted with chloroform-methanol (2:1), and the nonpolar lipids were isolated using silicic acid column chromatography eluted with chloroform. Samples were normalized to the culture OD, subjected to LC-MS, and quantitated using vitamin K1 as an internal recovery standard to derive the relative detector response. MK-9(II-H₂) is in black, and MK-9 is diagonally striped. By day 4, the levels of MK-9 had fallen to near the limit of detection.