Characterization and Phenotypic Control of the Cytochrome Content of Escherichia Coli

1. Electron-transport particles derived from Escherichia coli grown aerobically contain three b-type cytochromes with mid-point oxidation-reduction potentials at pH7 of +260mV, +80mV and -50mV, with n=1 for each. The variation of these values with pH was determined. 2. E. coli develops a different set of b-type cytochromes when grown anaerobically on glycerol with fumarate or nitrate as terminal electron acceptor. Electron-transport particles of fumarate-grown cells contain b-type cytochromes with mid-point potentials at pH7 of +140mV and +250mV (n=1). These two cytochromes are also present in cells grown with nitrate as terminal acceptor, where an additional cytochrome b with a mid-point potential of +10mV (n=1) is developed. 3. The wavelengths of the alpha-absorption-band maxima of the b-type cytochromes at 77K were: (a) for aerobically grown cells, cytochrome b (E(m7) +260mV), 556nm and 563nm, cytochrome b (E(m7) +80mV), 556nm and cytochrome b (E(m7)-50mV), 558nm; (b) for anaerobically grown cells, cytochrome b (E(m7) +250mV), 558nm, cytochrome b (E(m7) +40mV), 555nm and cytochrome b (E(m7) +10mV), 556nm. 4. Cytochrome d was found to have a mid-point potential at pH7 of +280mV (n=1). 5. Cytochrome a(1) was resolved as two components of equal magnitude with mid-point potentials of +260mV and +160mV (n=1). 6. Redox titrations performed in the presence of CO showed that one of the b-type cytochromes in the aerobically grown cultures was reduced, even at the upper limits of our range of electrode potentials (above +400mV). Cytochrome d was also not oxidizable in the presence of CO. Neither of the cytochromes a(1) was affected by the presence of CO.