Acetoacetic acid utilization is required for optimal growth of R. capsulatus SB1003 on Fe(III)-citrate. Wild-type R. capsulatus SB1003 and a mutant with a deletion of two genes (RRC00247 and RRC00248) involved in utilization of acetoacetic acid were tested for photoheterotrophic growth in the presence of Fe(III)-citrate. Cultures were incubated in medium containing 5 mM Fe(III) and 10 mM citrate in the light, and the absorbance at 600 nm was measured over time. ⧫, wild-type/pMQ131 (vector control); +, wild-type/pNC008 (with RRC00247 to RRC00248); ▵, ΔRRC00247-RRC00248/pMQ131 (vector control); •, ΔRRC00247-RRC00248/pNC008 (with RRC00247 to RRC00248). Data are representative of triplicate cultures.