The Research About Toxicology Mechanism Of Arsenic In A Protozoan,tetrahymena Corlissi

With the development of the social economy, a large number of pollutants are released into the environment and the pollution of arsenic has become one of the most important environment problems that human being concerned. Inorganic As can be biotransformed in the environment in several ways, such as oxidation, reduction, and methylation, which is significant for arsenic bioremediation. However, the mechanism of arsenic biotransformation has not been elucidated clearly at present, and the work of arsenic bioremediation moves slowly. So it is important to discover more arsenic resistant organisms and study the mechanism of arsenic biotransformation.Tetrahymena are a group of unicellular eukaryotes which are widespread in aquatic environments. And it has been early applied in the study of toxicology and environmental toxicology, especially Tetrahymena pyriformis is used as one of the model organisms in environmental toxicology. In this study we found T. corlissi has more ultra-high tolerance to arsenic than that of T. pyriformis and study the molecular basis for the high ability to provide an important reference for the bio-prevention of arsenic.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. It illustrates T. corlissi has the tolerance to arsenic that is the same as T. pyriformis and higher tolerance to arsenic than other aquatic animals and plants. Then the arsenite methltransferase gene(Ars M) was cloned in T. corlissi, and expressed under arsenic and non-arsenic exposure by RT-PCR. Finally, 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 ultra-high tolerance to arsenic.