Cytochromes of Escherichia coli

Abstract

Difference spectra and fourth-order finite difference analysis of spectra of E. coli measured at room temperature and 77 °K indicate that the alpha band previously attributed to cytochrome b 1 is a composite of the absorption bands of five or more different pigments. From the wavelengths of absorption maxima, these bands are tentatively assigned to at least two different c-type cytochromes and three b-type cytochromes. The ratios of the different cytochromes in cells grown aerobically and anaerobically vary considerably depending upon carbon source, growth phase, and strain. However, the same set of absorption bands was detected under all conditions examined. A comparison of the wavelengths of the observed bands with the wavelengths of alpha absorption bands of cytochromes found in other systems indicates that the b- and c-type cytochromes of E. coli are spectroscopically similar to those found in many other microorganisms and mitochondria.