title: Modification of cell volume and proliferative capacity of Pseudokirchneriella subcapitata cells exposed to metal stress.
abstract: The impact of metals (Cd, Cr, Cu and Zn) on growth, cell volume and cell division of the freshwater alga Pseudokirchneriella subcapitata exposed over a period of 72 h was investigated. The algal cells were exposed to three nominal concentrations of each metal: low (closed to 72 h-EC10 values), intermediate (closed to 72 h-EC50 values) and high (upper than 72 h-EC90 values). The exposure to low metal concentrations resulted in a decrease of cell volume. On the contrary, for the highest metal concentrations an increase of cell volume was observed; this effect was particularly notorious for Cd and less pronounced for Zn. Two behaviours were found when algal cells were exposed to intermediate concentrations of metals: Cu(II) and Cr(VI) induced a reduction of cell volume, while Cd(II) and Zn(II) provoked an opposite effect. The simultaneous nucleus staining and cell image analysis, allowed distinguishing three phases in P. subcapitata cell cycle: growth of mother cell; cell division, which includes two divisions of the nucleus; and, release of four autospores. The exposure of P. subcapitata cells to the highest metal concentrations resulted in the arrest of cell growth before the first nucleus division [for Cr(VI) and Cu(II)] or after the second nucleus division but before the cytokinesis (release of autospores) when exposed to Cd(II). The different impact of metals on algal cell volume and cell-cycle progression, suggests that different toxicity mechanisms underlie the action of different metals studied. The simultaneous nucleus staining and cell image analysis, used in the present work, can be a useful tool in the analysis of the toxicity of the pollutants, in P. subcapitata, and help in the elucidation of their different modes of action.
authors.affiliation: Bioengineering Laboratory-CIETI, Chemical Engineering Department, ISEP-School of Engineering of Polytechnic Institute of Porto, Rua Dr António Bernardino de Almeida, 431, 4200-072 Porto, Portugal; IBB-Institute for Biotechnology and Bioengineering, Centre for Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Manuela D
authors.initials: MD
authors.lastname: Machado
authors.affiliation: Bioengineering Laboratory-CIETI, Chemical Engineering Department, ISEP-School of Engineering of Polytechnic Institute of Porto, Rua Dr António Bernardino de Almeida, 431, 4200-072 Porto, Portugal; IBB-Institute for Biotechnology and Bioengineering, Centre for Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal. Electronic address: evs@isep.ipp.pt.
authors.forename: Eduardo V
authors.initials: EV
authors.lastname: Soares
mesh_terms: D049109:Cell Proliferation / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D000460:Chlorophyta / Q000166:cytology / Q000187:drug effects*; D019216:Metals, Heavy / Q000633:toxicity*; D013312:Stress, Physiological / Q000187:drug effects; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D019216:Metals, Heavy; D014874:Water Pollutants, Chemical
keywords: Algal growth; Biovolume; Cell division; Cell proliferation; Cell size; Metal toxicity