Oxidative stress induced by copper: defense and damage in the marine planktonic diatom Ditylum brightwellii, grown in continuous cultures with high and low zinc levels

Abstract

Light-limited cultures of the planktonic diatomDitylum brightwellii (West) Grunow were grown at 14%o salinity. Cells were subjected to oxidative stress induced by copper, in the presence of zinc. In two continuous cultures with total Zn levels of 40 and 140 nM, respectively, dissolved Cu levels were increased from 3 to 126 nM. This resulted in an increased Cu adsorption capacity of the cell walls, probably due to an increase of surface area and roughness. Sexual reproduction (auxospore formation) was accelerated but was considered as a non-specific stress response. Cu-induced oxidative stress was indicated by a decrease of reduced glutathione (GSH), and a removal of superoxide anions monitored as an increasing activity of superoxide dismutase (SOD). Although Zn has no oxidative potential per se, cell division rates and chlorophyll c contents were lower in the culture with high Zn levels. In both cultures, the pro-oxidant Cu caused a decrease of chlorophyll a, decreasing photosynthetic 02 evolution and cell devision rates, and a growing number of deformed and broken cells.

Toxicity and bioaccumulation of copper in three green microalgal species

“…Enteromorpha, which is frequently used as an indicator species for heavy metal contamination, contained relatively great concentration of Cu (Rijstenbil et al, 1998a,b). The chelation removal of heavy metals from the cell surface after the binding of Cu with organic complexes (including cell exudates) is another possible mechanism for the detoxification of metal ions (Xue et al, 1988;Xue and Sigg, 1990;Rijstenbil et al, 1994;Gerringa et al, 1995).…”

“…Binding to organic complexes, especially cell exudates, is another possible mechanism regulating the detoxification of metal ions (Xue et al, 1988;Xue and Sigg, 1990;Rijstenbil et al, 1994;Gerringa et al, 1995). It has been reported that microalgal production of glutathione, thiols or superoxide dismutase activity (SOD) can be stimulated by copper, which may also be a defense mechanism against copper toxicity (Rijstenbil et al, 1994(Rijstenbil et al, , 1998aRijstenbil and Wijnholds, 1996;Okamoto and Colepicolo, 1998;Leal et al, 1999).…”

Chlorophyll a Fluorescence as a Probe of Heavy Metal Ion Toxicity in Plants

“…Chi a fluorescence measurements show a site of Cu inhibition on the PS II antenna (Lidon and Henriques, 1993). Cu was also shown to be competing for other physiological metal ion sites, like Ca, at PS II, and that it may induce electron transport at PS II (Rijstenbil et al, 1994;Patsikka et al, 1998a,b). Time-resolved fluorescence decay analysis showed that Cu does not affect primary charge separation but destabilizes the charge stabilization (Yruela et al 1996b).…”

Heavy Metal-Induced Oxidative Stress in Plants: Response of the Antioxidative System

“…As seen in algae (Scenedesmus sp. ), the binding of metals to thiols can protect cell metabolism from metal toxicity only temporarily; however, during severe stress, depletion of thiol pool is known to make cells vulnerable to oxidative stress (Rijstenbil et al 1994). Depletion of thiol content in Scenedesmus sp.…”