原生动物柯立斯四膜虫(Tetrahymena corlissi)超高砷耐受性的分子机制研究

Molecular Mechanism of High Tolerance to Arsenic in a Protozoan, Tetrahymena corlissi

以原生动物柯立斯四膜虫(Tetrahymena corlissi)为实验对象,通过流式细胞仪测定细胞密度分析四膜虫相对生长率,得到砷暴露下T.corlissi 24 h的半数效应浓度(EC50)为110.7μg/m L,是梨形四膜虫(T.pyriformis)的3倍;在克隆到T.corlissi砷甲基转移酶(Ars M)基因的基础上,RT-PCR结果显示,该基因在砷暴露下表达;利用高效液相色谱-电感耦合等离子体质谱仪(HPLC-ICP-MS)联用方法对细胞内砷形态的检测显示,野生型T.corlissi具有比T.pyriformis强数倍的甲基化砷的能力,Ars M基因敲除的T.corlissi失去了甲基化砷的能力,从而推测T.corlissi的Ars M具有高效甲基化砷的能力,是其具有超高的砷耐受性的分子基础.

In this study, the half maximum effective concentrations（EC50） of Tetrahymena, under 24 h arsenic exposure, were measured by detecting cell density using flow cytometry. The EC50 of T. corlissi is 110.7 ug/m L, which is three times that of T. pyriformis. The arsenite methltransferase gene（Ars M） was cloned in T. corlissi, and expressed under arsenic exposure. The arsenic speciation analysis in vivo by HPLC-ICP-MS showed that T. corlissi has a much greater ability to methylate arsenic than does T. pyriformis. Also Ars M knock-out T. corlissi lost the ability to methylate arsenic. This indicated that the more effective Ars M of T. corlissi could result in its high tolerance to arsenic.