Figure 4.

Representative ¹H NMR spectra with key resonances labeled. Although the crowded region between 3.59 and 3.92 ppm contains the resonances of several metabolites, the predominant peaks in this region are those of trehalose. (A) Spectra of extracts of the pnit-6_1.5 strain cultured on VM-Gln (top) or VM-nitrate (bottom). The resonances of Gln and Glu are increased when Gln is used as a nitrogen source, whereas the levels of Ala, mannitol, and trehalose are more intense when the strain is grown on nitrate-containing media (see also Figure S3 and Figure S4). (B) Spectra of extracts of the ptcu-1_1.5 strain cultured on media containing in BCS (top) and CuSO₄ (bottom). These spectra are more similar than those shown in (A), with the most pronounced differences in the regions containing the resonances of BCS (see also Figure S5).