title: UV-B effects on Antarctic Chlorella sp cells.
abstract: Growth of Antarctic Chlorella sp cells was measured in cultures irradiated with 30 kJ m(-2) UV-B (280-320 nm). The specific growth rate immediately after the lag phase was 0.36+/-0.06 and 0.26+/-0.03 day(-1) for unirradiated cultures and cultures irradiated with UV-B, respectively, UV-B irradiation significantly decreased ascorbate content by 54.5%, and increased the ascorbyl radical content/ascorbate content ratio by 2.25-fold in algae cultures in log phase. UV-B exposure significantly decreased by 95, 62 and 71% the content of alpha-tocopherol, beta-carotene and total thiols, respectively, in cells in log phase of development. The cellular content of alpha-tocopherol, beta-carotene and total thiols was reduced by 78, 43 and 44%, respectively in stationary phase, as compared to the antioxidant content in the cells during log phase of development. UV-B exposure reduced the content of alpha-tocopherol and total thiols in stationary phase of development by 64 and 91%, respectively, as compared to unirradiated cells. The content of beta-carotene in stationary phase was not affected by UV-B exposure. The results presented here suggest that increased UV-B radiation was responsible for the development of oxidative stress conditions, assessed as the ascorbyl radical content/ascorbate content ratio, in Antarctic Chlorella sp cells. Moreover, a significant decrease in the content of both lipid and water soluble antioxidants might contribute to establish oxidative stress in the cells.
authors.affiliation: Physical Chemistry-PRALIB, School of Pharmacy and Biochemistry, University of Buenos Aires, Argentina. susanap@ffyb.uba.ar
authors.forename: M S
authors.initials: MS
authors.lastname: Estevez
authors.forename: G
authors.initials: G
authors.lastname: Malanga
authors.forename: S
authors.initials: S
authors.lastname: Puntarulo
mesh_terms: D000864:Antarctic Regions; D001205:Ascorbic Acid / Q000378:metabolism; D002708:Chlorella / Q000254:growth & development / Q000528:radiation effects*; D007700:Kinetics; D014466:Ultraviolet Rays
chemical_list: D001205:Ascorbic Acid