RuBPCase，protein，and bacteriochlorophyll assay
RuBPCase activity was assayed with toluene-treated cells based on the method of Tabita et al.［28］，with some minor modifications.Samples（20 ml）of cells were harvested，washed twice in 10 ml of cold Tris（50 mmol/L）-EDTA（10 mmol/L）buffer（pH 8.0），and then suspended in 2 ml of the same buffer.A l-ml amount of cold toluene was added and mixed，and the cells were kept on ice for 10 min.After centrifugation at 5，000 rpm for 10 min，the cells were washed with Tris-EDTA buffer and suspended in 1 ml of the same buffer.Reactions were performed in scintillation minivials with rubber stoppers and contained the following：0.05 ml of 50 mmol/L MgCl2，50 mmol/L N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid（pH 7.2），0.05 ml of 100 mmol/L NaH14CO3（specific activity，300 to 1，000 cpm/nmol），0.05 ml of toluene-treated cell suspension，0.025 ml of 10 mmol/L RuBP，and 0.075 ml of water.All components minus the RuBP were mixed and preincubated for 10 min at 33℃to activate the enzyme.Prewarmed RuBP was added to initiate the reaction.The assay was performed at 33℃for 3 to 5 min and stopped with the injection of 0.025 ml of 6 N HCl.The reaction mixture was dried down at 80℃under N2 in a fume hood，allowed to cool，and suspended in 0.1 ml of water.The samples were then counted in Tritosoh22］.One unit of RuBPCase is defined as the amount of enzyme needed to carboxylate 1 μmol of RuBP in 1 min at 23℃.
Protein concentrations were determined by a modified Lowry procedure［19］.The total bacteriochlorophyll（Bchl）content of the cells was estimated by absorbancy measurements at 775 nm of acetone-methanol（7∶2，vol/vol）extracts with an extinction value of 75 mmol/L［9］.(https://www.daowen.com)
