Pigment Extraction and Chromatophore Preparation

Total cellular pigments（bacteriochlorophyll and carotenoids）of 10 ml of cells were extracted with and dissolved in 10 ml of acetone-methanol（7∶2，vol/vol）for spectroscopic analysis as previously described9］.For the chromatophore absorption study 5 ml of photosynthetically or aerobically grown cells was harvested and suspended in 1 ml of Tris（5 mmol/L，pH 8.0）-EDTA（5 mmol/L）buffer as described previously［39］.The absorption spectra of the pigments in acetone-methanol and of chromatophores in Tris-EDTA buffer were measured in a Cary 118 and a Varian 2300 spectrophotometer，respectively，based on total cell number or amounts of protein.Protein concentrations were assayed by a modified Lowry method［23］.(https://www.daowen.com)