title: Changes in metabolites, antioxidant system, and gene expression in Microcystis aeruginosa under sodium chloride stress.
abstract: Microcystis (M.) aeruginosa, one of the most common bloom-forming cyanobacteria, occurs worldwide. The Qingcaosha (QCS) Reservoir is undergoing eutrophication and faces the problem of saltwater intrusion. The aim of this study was to investigate the effects of sudden salinity changes on physiological parameters and related gene transcription in M. aeruginosa under controlled laboratory conditions. The results showed that sodium chloride (50, 200 and 500 mg L(-1) NaCl) inhibited the algal growth and decreased pigment concentrations (chlorophyll a, carotenoid and phycocyanin). Sodium chloride increased both the intracellular and extracellular microcystin contents and elevated the mcyD transcript level in M. aeruginosa. It also increased the malondialdehyde (MDA) content and caused cytomembrane damage. This damage caused the release of intracellular toxins into the culture medium. In addition, NaCl decreased the maximum electron transport rate, increased the levels of reactive oxygen species (ROS) and changed the cellular redox status. Consequently, NaCl inhibited the expression of cpcB, psbA and rbcL. Furthermore, NaCl increased the activities of superoxide dismutases (SOD), catalase (CAT), glutathione reductase (GR), and total glutathione peroxidase (GPx). The transcript levels of sod and reduced glutathione (gsh) were also increased after exposure to NaCl. Our results indicate that a sudden increase in salinity increases the production and excretion of microcystin, changes the cellular redox status, enhances the activities of antioxidant enzymes, inhibits photosynthesis, and affects transcript levels of related genes in M. aeruginosa.
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China.
authors.forename: Feijian
authors.initials: F
authors.lastname: Mao
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China.
authors.forename: George Chira
authors.initials: GC
authors.lastname: Kirumba
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China; Institute of Energy Conversion, Jiangxi Academy of Sciences, Nanchang 330096, PR China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Jiang
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Mike
authors.initials: M
authors.lastname: Manefield
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China. Electronic address: ylhe@sjtu.edu.cn.
authors.forename: Yiliang
authors.initials: Y
authors.lastname: He
mesh_terms: D002338:Carotenoids / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D004579:Electron Transport; D015870:Gene Expression / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D008315:Malondialdehyde / Q000378:metabolism; D052998:Microcystins / Q000378:metabolism; D046931:Microcystis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000187:drug effects; D010798:Phycocyanin / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D054712:Salinity; D012965:Sodium Chloride / Q000633:toxicity*; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D052998:Microcystins; D017382:Reactive Oxygen Species; D010798:Phycocyanin; D002734:Chlorophyll; D002338:Carotenoids; D012965:Sodium Chloride; D008315:Malondialdehyde; C078588:microcystin; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005978:Glutathione; D000077194:Chlorophyll A
keywords: Enzyme assay; Gene expression; Microcystin; Microcystis aeruginosa; Sodium chloride