Metabolic Regulation of Mycobacterial Growth and Antibiotic Sensitivity
Figure 1
Triglyceride synthesis mutants continue to replicate under growth-limiting conditions.
(A) The predicted TAG biosynthetic pathway of M. tuberculosis and its relationship to the TCA cycle. Mutations in the underlined genes were predicted by Transposon Site Hybridization to result in overrepresentation after hypoxia. OAA, oxaloacetate; MAG, monoacylglycerol; DAG, diacylglycerol. (B) Δtgs1 bacteria grow to a higher cell density in hypoxic cultures. (C) Δtgs1 mutants continue to replicate in hypoxic culture. The replication dynamics of the indicated strains were assessed by quantifying the rate at which unstable plasmid pBP10 was lost (right axis, open symbols). The “cumulative bacterial number” (left axis, closed symbols) represents the total number of organisms that would have been present if cell death was negated. Arrows in (B) and (C) indicate the initiation of hypoxia based on methylene blue decolorization. (D and E) Growth of M. tuberculosis strains at an initial pH of 5.5 (D) and in low iron medium (E). Optical density measurements are shown (similar data were obtained by quantifying CFU). Means ± SD of two independent experiments each performed in duplicate or triplicate are shown. Insets demonstrate the lack of TAG accumulation (upper species) in Δtgs1 bacteria, as assessed by thin layer chromatography. Each TLC was developed independently. In inset, “a,” H37Rv; “b,” Δtgs1; and “c,” complemented strain Δtgs1+pTGS1.