Fig. 1

Inactivation of homoserine dehydrogenase and homoserine kinase is bactericidal. a The aspartate family amino acid biosynthesis pathway (aspartate pathway) in M. tuberculosis including the lysine degradation (aminoadipate) pathway. Ask: aspartate kinase, Asd: aspartate semialdehyde dehydrogenase, ThrA: threonine dehydrogenase, MetX: homoserine transacetylase, ThrB: homoserine kinase, ThrC: threonine synthase, MetK: S-adenosyl methionine synthase, DapE: Succinyl-diaminopimelate desuccinylase, LysE: lysine exporter, Pcd: aminoadipate semialdehyde dehydrogenase, Lat: lysine transacetylase. Two mutants were constructed, one threonine auxotroph Mtb ∆thrB and Mtb ∆thrA, a strain auxotrophic for both, threonine and methionine. b, d Growth measured by optical density OD₆₀₀. c, e Survival curves measured by colony forming units (CFU). b Deletion of thrB can be chemically complemented by threonine (Thr) (blue inverted triangles) but not isoleucine (Ile). c Deletion of thrB is bactericidal and mirrors the kill curve of Mtb ∆thrA supplemented with methionine (Met) (open rhombus). d Deletion of thrA can be chemically complemented by homoserine (Hse) (black circles) or a combination of threonine and methionine (blue triangles), but not by threonine, isoleucine (orange diamonds) and methionine alone (purple rhombus). e Deletion of thrA is bactericidal. Cell death of Mtb ∆thrA can be slowed by addition of threonine or methionine but not isoleucine, indicating that inhibition of each individual branch (threonine and methionine) contributes to killing. All values are the average of three biological replicates (n = 3) ± s.d. (error bars show standard deviation) and are representative of a minimum of two independent experiments. **p-value < 0.01 in Student's t-test. Source data are provided as a Source Data file