M. tuberculosis H37Rv wt was grown in HdB medium (pH 5.5) supplemented with one of the 20 natural amino acids as the sole nitrogen source. The cell density (OD600) of the culture (A), the pH (B) and the ammonia concentration (C) were measured every two days. w/o AA* indicates that M. tuberculosis in all cultures except those containing asparagine (Asn), glutamine (Gln), glutamic acid (Glu) and aspartic acid (Asp) gave similar growth curves and pH change to the culture without any amino acids supplemented. Cysteine was removed from graph B as it interfered with the assay. For clarity, cultures with amino acid supplements that did not give rise to detectable changes in optical density, pH, or ammonia levels were omitted from graph C except for the culture with no amino acid supplements (filled black circles).