共生细菌对盐生小球藻亚砷酸盐代谢的影响

为探讨共生细菌对盐生小球藻（Chlorella salina）亚砷酸盐（As（III））富集和形态转化的影响，从C.salina培养液中分离培养出一株共生细菌，并采用抗生素处理C.salina获得无菌藻，设置0，75，150，300，750 μg/LAs（III）溶液处理带菌和无菌的C.salina，7d后测定C.salina对As（III）的吸收、吸附和富集量，以及培养液和藻细胞内As的形态，计算带菌和无菌C.salina对As（III）的氧化率和去除率；使用不同浓度的As（III）处理共生细菌7d，并以300μg/L的As（III）处理共生细菌不同时间，计算两种情况下共生细菌对培养液中As（III）的氧化率和去除率.结果表明：C.salina的共生细菌为根癌农杆菌（Agrobacterium tumefaciens WB-1）；与无菌C.salina相比，带菌C.salina生长更快、对As（III）的耐性更强.带菌C.salina对As（III）的富集量为103.10~448.12mg/kg、氧化率为78.93%~96.88%、去除率为18.92%~55.21%，显著高于无菌C.salina的富集量（11.68~91.39mg/kg）、氧化率（14.46%~26.39%）和去除率（12.82%~29.15%），也高于A.tumefaciens WB-1对As（III）的氧化率（4.51%~30.61%）和去除率（1.86%~16.19%）.此外，带菌C.salina胞内还检测到少量的As（III）和甲基砷，而在无菌C.salina胞内没有甲基砷存在.共生细菌促进了盐生小球藻对As（III）的富集和形态转化.

Effect of a symbiotic bacterium on the accumulation and transformation of arsenite by Chlorella salina

In order to investigate the effects of a symbiotic bacterium on arsenite (As(III)) accumulation and transformation of C. salina, one symbiotic bacterial strain was isolated from culture medium of C. salina. Antibiotics were added to C. salina to obtain the axenic microalga, and a series of As(III) treatments (0, 75, 150, 300, 750mg/L) were applied to the non-axenic and axenic C. salina. After 7 days, the absorption, adsorption and accumulation of As(III) by C. salina were determined. The As speciation in the culture and algal cells were also analyzed and the rates of As(III) oxidation and removal by non-axenic and axenic C. salina were calculated. At the same time, the symbiotic bacterium was treated with different concentrations of As(III) for 7days, and with 300mg/L As(III) for different time. The oxidation and removal rates of As(III) in the bacterial culture medium were then calculated. Results show that the symbiotic bacterium was identified as Agrobacterium tumefacienss WB-1. Compared with the axenic C. salina, the non-axenic C. salina grew faster with higher tolerance to As(III). Moreover, in the presence of bacterium, As(III) accumulation by C. salina from the culture solution varied from 103.10 to 448.12mg/kg, the oxidation and removal rates of As(III) were 78.93%~96.88% and 18.92%~55.21%, respectively. These values were significantly higher than those of the axenic C. salina, which varied from 11.68 to 91.39mg/kg, 14.46%~26.39% and 12.82%~29.15%, respectively. The As(III) oxidation and removal rates in the non-axenic C. salina culture were also significantly higher than those in the A. tumefaciens cuture (4.51%~30.61% and 1.86%~16.19%, respectively). In addition, a small amounts of As(III) and methylated As were detected in the cells of non-axenic C. salina, while no methylated As was present in the axenic C. salina cells. Symbiotic bacteria promote the enrichment and transformation of As(III) by Chlorella salina.