Bacterial strains，media，and growth conditions

R.sphaeroides wild-type strain 2.4.1 was used throughout.The cells were grown on modified Sistrom medium A［26］supplemented with 0.4%butyrate and 0.1%NaHCO3 as the carbon source unless otherwise noted.The cells were fully adapted to the butyrate medium before inoculation.Those cells undergoing photoheterotrophic growth were grown at 30℃on the butyrate medium in completely filled flat screwcap bottles（100 ml）normally at nearsaturating light intensity（10 W/m2），provided by a bank of lumiline lamps（General Electric Co.）.When light intensity was to be a variable，the cells were also grown under conditions designated low light intensity at 3 W/m2 in comparison with 10 W/m2，designated as the high intensity light.The light energy was measured with a Yellow Springs-Kettering model 6.5A radiometer through a coming colored-glass filter（CS No.7-69；620 to 1，100 nm）.Dark-shift experiments were performed by wrapping the growth vessels from high lightgrown cells with aluminum foil for 1 h at 30℃.Partial aerobic growth was maintained by chemoheterotrophic culturing of the cells（100 ml in a 500-ml flask）on a gyratory shaker at 30℃.In some cases the culture（100 ml）was sparged with a gas mixture of O2-N2-CO2（25 74∶1）to obtain high O2 partial pressure；such conditions are designated full aerobic growth［5］.In addition to butyrate，malate and succinate（0.4%）were also used as carbon sources in certain experiments.Cell growth was routinely monitored turbidimetrically with a Klett-Summerson colorimeter（Klett Manufacturing Co.，Inc.）equipped with a No.66 filter.One Klett unit is equivalent to a cell density of approximately 107cells per ml.Chemoheterotrophically grown cells and photoheterotrophically grown cells were harvested at the cell densities indicated below.(https://www.daowen.com)