title: Zinc-induced differential oxidative stress and antioxidant responses in Chlorella sorokiniana and Scenedesmus acuminatus.
abstract: Algae are frequently exposed to toxic metals, and zinc (Zn) is one of the major toxicants present. We exposed two green microalgae, Chlorella sorokiniana and Scenedesmus acuminatus, to sub-lethal concentrations (1.0 and 0.6mM) of Zn for seven days. Algal responses were analysed at the level of growth, oxidative stress, and antioxidants. Growth parameters such as cell culture yield and pigment content were less affected by Zn in C. sorokiniana, despite the fact that this alga accumulated more zinc than S. acuminatus. Also, C. sorokiniana, but not S. acuminatus, was able to acclimatize during long-term exposure to toxic concentrations of the test metals (specific growth rate (µ) was 0.041/day and total chlorophyll was 14.6mg/mL). Although, Zn induced oxidative stress in both species, C. sorokiniana experienced less stress than S. acuminatus. This could be explained by a higher accumulation of antioxidants in C. sorokiniana, where flavonoids, polyphenols, tocopherols, glutathione (GSH) and ascorbate (ASC) content increased. Moreover, antioxidant enzymes glutathione S transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD), peroxidase (POX) and ascorbate peroxidase (APX), showed increased activities in C. sorokiniana. In addition to, and probably also underlying, the higher Zn tolerance in C. sorokiniana, this alga also showed higher Zn biosorption capacity. Use of C. sorokiniana as a bio-remediator, could be considered.
authors.affiliation: Department of Soil Microbiology, Soils Water and Environment Research Institute, Agricultural Research Center, Giza, Egypt. Electronic address: seham_moussa939@yahoo.com.
authors.forename: Seham M
authors.initials: SM
authors.lastname: Hamed
authors.affiliation: Integrated Molecular Plant Physiology Research, Department of Biology, University of Antwerp, Antwerp, Belgium; Centre of Excellence PLECO (Plant and Vegetation Ecology), Department of Biology, University of Antwerp, Antwerp, Belgium.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Zinta
authors.affiliation: Hochschule Bremen, University of Applied Sciences, Bremen, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Klöck
authors.affiliation: Integrated Molecular Plant Physiology Research, Department of Biology, University of Antwerp, Antwerp, Belgium.
authors.forename: Han
authors.initials: H
authors.lastname: Asard
authors.affiliation: Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, Aljouf University, Sakaka, P.O. 2014, Saudi Arabia; Microbiology and Botany Department, Faculty of Science, Suez Canal University, Ismailia, P.O.Box 41522, Egypt.
authors.forename: Samy
authors.initials: S
authors.lastname: Selim
authors.affiliation: Integrated Molecular Plant Physiology Research, Department of Biology, University of Antwerp, Antwerp, Belgium; Department of Botany & Microbiology, Faculty of Science, University of Beni-Suef, Beni-Suef 62511, Egypt. Electronic address: hamada.abdelgawad@uantwerpen.be.
authors.forename: Hamada
authors.initials: H
authors.lastname: AbdElgawad
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D060387:Ascorbate Peroxidases / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism; D002708:Chlorella / Q000187:drug effects* / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D019216:Metals, Heavy / Q000633:toxicity; D018384:Oxidative Stress / Q000187:drug effects*; D010088:Oxidoreductases / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D044444:Scenedesmus / Q000187:drug effects* / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D015032:Zinc / Q000633:toxicity*
chemical_list: D000975:Antioxidants; D019216:Metals, Heavy; D002734:Chlorophyll; D010088:Oxidoreductases; D010544:Peroxidases; D060387:Ascorbate Peroxidases; D009195:Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005978:Glutathione; D015032:Zinc; D001205:Ascorbic Acid
keywords: Antioxidants; Green microalgae; Oxidative stress; Zinc; Zinc detoxification