title: Mechanisms of photosynthetic inactivation on growth suppression of Microcystis aeruginosa under UV-C stress.
abstract: This study aims to investigate the effects of UV-C irradiation on photosynthetic processes of Microcystis aeruginosa to unravel the mechanism(s) involved in how and in what ways UV-C mediates growth suppression and cellular recovery. Changes in the concentration of photosynthetic pigments, photochemical efficiency, PS II core protein (D1) content, and the coding genes expressions were measured. The results indicate that UV-C doses at 20-200 mJ cm(-2) lead to rapid reduction in gene expression of both psbA (for D1) and cpc (for phycocyanin), but the suppression was short term and recoverable within 3 d of post-UV incubation. Conversely, UV-C doses at ≥50 mJ cm(-2) could induce marked decline in photochemical efficiency (represented by the optimal PS II quantum yield, FV/FM, and the effective PS II quantum yield, Y) as well as decreases in D1 content and water soluble pigments (phycoerythrins, phycocyanins, allophycocyanins) in M. aeruginosa during the post UV-C incubation period. The results suggest that interruption of both the light energy harvesting apparatus (especially the water soluble pigments) and the photochemical process mainly accounted for the growth suppression effect in UV-C irradiated M. aeruginosa.
authors.affiliation: Key Laboratory of Microorganism Application and Risk Control (MARC) of Shenzhen, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China; State Key Laboratory on Marine Pollution, Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: Yi
authors.initials: Y
authors.lastname: Tao
authors.forename: Xianzhong
authors.initials: X
authors.lastname: Mao
authors.forename: Jiangyong
authors.initials: J
authors.lastname: Hu
authors.forename: H O L
authors.initials: HO
authors.lastname: Mok
authors.forename: Lingyun
authors.initials: L
authors.lastname: Wang
authors.forename: D W T
authors.initials: DW
authors.lastname: Au
authors.forename: Jia
authors.initials: J
authors.lastname: Zhu
authors.forename: Xihui
authors.initials: X
authors.lastname: Zhang
mesh_terms: D015870:Gene Expression / Q000528:radiation effects*; D046931:Microcystis / Q000254:growth & development / Q000528:radiation effects*; D010788:Photosynthesis / Q000528:radiation effects*; D045332:Photosystem II Protein Complex; D013312:Stress, Physiological; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods; D018508:Water Purification / Q000379:methods
chemical_list: D045332:Photosystem II Protein Complex
keywords: Gene expression; Microcystis aeruginosa; Photoinhibition; Photosystem II; Phycobilisome; UV-C irradiation