Figure 1: In vivo hydrocarbon formation from CO reduction by A. vinelandii.
From: The in vivo hydrocarbon formation by vanadium nitrogenase follows a secondary metabolic pathway
(a) Growth curves of A. vinelandii strains expressing Mo (black)- and V (blue)-nitrogenases in the presence (open circles) and absence (open triangles) of 10% CO. The arrows indicate the time points of CO addition to the two cultures, when ammonia was depleted and nitrogenase expression was turned on. (b) Time-dependent formation of C2H4, C2H6 and C3H8 by 250 ml cultures of A. vinelandii strains expressing Mo (black)- and V (blue)-nitrogenases. The 250 ml culture expressing the V-nitrogenase yielded 1,387 nmol C2H4, 63 nmol C2H6 and 8 nmol C3H8, respectively, when 1.7 mmol CO was supplied in a 250 ml gas phase. (c) GC–MS analysis of C2H4 (upper), C2H6 (middle) and C3H8 (lower) formed by A. vinelandii strain expressing V-nitrogenase in the presence of 12CO (left) and 13CO (right). The products were traced in the SIM mode of GC–MS at masses indicated in the figure. The peak intensities of products generated by the culture expressing the V-nitrogenase (blue) were set at 100%. The absence of product formation when CO was supplied to controls that either expressed the Mo-nitrogenase in the absence of ammonia (black) or did not express the V-nitrogenase in the presence of ammonia (red) is noteworthy. (d) GC–MS fragmentation patterns of C2H4 (, blue), C2H6 (, blue) and C3H8 (, blue) formed by the A. vinelandii strain expressing the V-nitrogenase in the presence of 12CO (left) and 13CO (right). The corresponding fragmentation patterns of standards are presented based on information obtained from the NIST MS database (black) (http://webbook.nist.gov). The intensities of base peaks were set at 100% in all panels. Data of cell growth and activity analysis (a,b) were obtained from three independent experiments (n=6) and presented as mean±s. d. GC–MS experiments (c,d) were conducted three times and representative results are shown.
