Abstract: We constructed consortia of Chlorella salina and Bacillus subtilis with various alga-bacterium ratios (1:0, 1:1, 1:2, 1:3, 1:4). After being treated with arsenate [As(Ⅴ)] for 7 d, we measured the growth, As accumulation, adsorption and absorption, and As speciation transformation of consortia. Results showed that the chlorophyll content, dry weight, and specific growth rate of the symbiont increased significantly with increasing B. subtilis ratio after the As(Ⅴ) treatment, being 1.81 mg·L^-1, 125.0 mg, and 0.28 mg·L^-1·d^-1 under the condition of the alga-bacterium ratio being 1∶4 and As(Ⅴ) being 750 μg·L^-1, respectively. The accumulation and absorption of As by the consortia decreased with the bacterial proportion increasing from 1:0 to 1:4. As accumulation changed with the As concentration, with a dominance of absorption under 75-150 μg·L^-1 As(Ⅴ) and a dominance of adsorption under 300-750 μg·L^-1As(V). There were As(Ⅴ) and As(Ⅲ) in the consortia. When the proportion of bacteria increased, the rate of As(Ⅴ) reduction enhanced (up to 12.6%). Our results indicated that the increases of B. subtilis improved As(Ⅴ) tolerance and reduction, but decreased the As(Ⅴ) accumulation by the symbiont.

Key words: algae-bacteria consortia, arsenate, growth, accumulation, speciation transformation