title: Arsenate toxicity and stress responses in the freshwater ciliate Tetrahymena pyriformis.
abstract: The arsenic metabolism in different biological organisms has been studied extensively. However, little is known about protozoa. Herein, we investigated the cell stress responses of the freshwater ciliate Tetrahymena pyriformis to arsenate toxicity. An acute toxicity assay revealed an 18-h EC(50) arsenate concentration of ca. 40 μM, which caused significant changes in the cell shape, growth and organism mobility. Whereas, under exposure to 30 μM arsenate, T. pyriformis could grow reasonably well, indicating a certain resistance of this organism. Arsenic speciation analysis revealed that 94-98% of the total arsenate in cells of T. pyriformis could be transformed to monomethylarsonic acid, dimethylarsinic acid and a small proportion of arsenite after 18 h of arsenate exposure, thus indicating the major detoxification pathway by arsenic oxidation/reduction and biomethylation. Finally, comparative proteomic analysis unveiled significant changes in the expression of multiple proteins involved in anti-oxidation, sugar and energy metabolism, proteolysis, and signal transduction. Our results revealed multiple pathways of arsenate detoxification in T. pyriformis, and indicated that protozoa may play important roles in the biogeochemical cycles of arsenic.
authors.affiliation: Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
authors.forename: Yong-Yu
authors.initials: YY
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Xi-Xiang
authors.initials: XX
authors.lastname: Yin
authors.forename: Su-Ping
authors.initials: SP
authors.lastname: Yang
authors.forename: Yong-Guan
authors.initials: YG
authors.lastname: Zhu
mesh_terms: D001149:Arsenates / Q000378:metabolism / Q000633:toxicity*; D001711:Biotransformation; D002470:Cell Survival / Q000187:drug effects; D005618:Fresh Water / Q000469:parasitology; D008124:Locomotion / Q000187:drug effects; D020543:Proteome / Q000032:analysis; D015800:Protozoan Proteins / Q000032:analysis; D013312:Stress, Physiological; D013769:Tetrahymena pyriformis / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D013997:Time Factors
chemical_list: D001149:Arsenates; D020543:Proteome; D015800:Protozoan Proteins; C025657:arsenic acid