Estimation of the expression of cytochromes in mixotrophically growing cells. The expression of cytochromes was determined under the following cultivation conditions, which allowed a high expression of photosynthetic pigments and mixotrophic growth in the respective strains: L. syltensis DSM 22749T was cultured in SYMHC medium under air atmosphere (red line), C. halotolerans DSM 23344T (blue line) and P. rubra DSM 19751T (green line) in defined medium containing 10 mM DL-malate at an initial head space gas atmosphere of 20% (v/v) O2. The position of distinct peaks of the spectra is indicated. A.U., arbitrary units of absorbance. A. Dithionite-reduced minus ferricyanide-oxidized redox difference spectra of extracts from whole cells solubilized with 0.3% (w/v) N,N-dimethyldodecylamine-N-oxide. Peaks at 424 and 553 nm indicate the presence of cytochrome c and the peak around 602 nm cytochrome a; shoulders in the Soret region at 434 and 445 nm the presence of cytochromes b and a, respectively. B. CO and dithionite-reduced minus dithionite-reduced difference spectra of intact cells. Troughs in the Soret region at 433 and 446 nm could indicate the binding of CO by heme b and aa3, respectively.