The mixed culture 'Chloropseudomonas ethylica' strain 2K has been grown on a medium which enhanced the yield of cytochrome c-551.5 from Desulfuromonas acetoxidans. The cytochrome was purified to homogeneity and an isoelectric point of 8.40 was determined. A determination of the amide content indicated that the cytochrome contains two more amides than previously reported.