Fig. 3. Pigment accumulation in E. coli strains expressing Chl biosynthesis genes.

(A) Photographs of cell pellets of the E. coli control strain accumulating PPIX (3a) and the Chl a–producing strain (DE/BoP/IG) grown with supplementation of δ-aminolevulinic acid (ALA). Pigment production in described E. coli strains was analyzed by HPLC. m/z, mass/charge ratio. (B) Accumulation of MgPME in the IM strain monitored by absorbance at 416 nm. (C) Accumulation of DV PChlide a in the IA strain monitored by absorbance at 440 nm. (D) Light-dependent production of MV Chlide a in the ID strain monitored by absorbance at 440 nm (shown in black) and 665 nm (shown in blue). POR was activated by treatment with 5 μmol photons m⁻² s⁻¹ light at the latter stage of the incubation. The small MV Chlide a peak detected in the dark sample is due to unavoidable light exposure during experimental procedures. DV and MV pigments are differentiated by positions of Soret bands in the absorption spectra. (E) Accumulation of GG–Chl a in the DE/IG strain and of Chl a in the DE/BoP/IG strain monitored by absorbance at 665 nm. The production of authentic Chl a was further confirmed by LC-MS with the acquired mass spectrum shown in the inset (see fig. S6 for details). The pigment accumulated in the IG strain was not assigned because of lack of an appropriate pigment standard.