Reversal of copper toxicity inamphora coffeaeformis: Role of externally bound copper

Aspects of copper tolerance and toxicity inAmphora coffeaeformis

“…Florence (1986, 1987) also found that the thiol cysteine can reverse copper toxicity, and proposed a toxicity mechanism involving intracellular thiols, particularly glutathione, which may affect mitosis. Robinson and Hall (1990) also observed reversal of copper toxicity by cysteine; however the effectiveness of very short exposures to cysteine, of the order of 5 min or less, suggests that the site of copper toxicity may lie at or very near the plasmalemma. The same study showed that an acid wash, and to a lesser extent, an EDTA or seawater wash also reversed copper toxicity, Downloaded by [McGill University Library] at 19:00 06 February 2015 suggesting that reversal was achieved by the removal of externally bound copper.…”

“…On the other hand, lipid-soluble copper complexes such as copper hydroxyquinoline (CuHQO) and copper hydroxyquinaldine (CuHQA), which are able to cross cell membranes (Florence & Stauber, 1986), are highly toxic to this species. This toxicity is not reversible by cysteine (Robinson & Hall, 1990), suggesting different toxicity mechanisms for the ionic and complexed forms of copper. Stauber and Florence (1987) examined copper toxicity mechanisms for three species of algae, and concluded that photosynthesis was strongly inhibited by copper in Asterionella glacialis and Chlorella pyrenoidosa, but not Nitzschia closterium.…”

“…Florence and Stauber (1986) have observed uptake of CuHQO by Nitzschia closterium followed by release of HQO and retention of the copper. The inability of cysteine to reverse the toxicity of HQO or HQA bound copper (Robinson & Hall, 1990) suggests that either the copper is inaccessible to cysteine, or that it is bound to a site with a higher binding constant than cysteine, or, alternatively, that the damage is so extensive as to be irreversible.…”

“…Evidence suggests that this pennate diatom is able to restrict the entry of ionic copper into the cell by binding it externally, possibly to mucilaginous exudate or to the surface of the cell (Brown et al, 1988). At sufficiently high concentrations, copper does inhibit growth in this species; this however is completely reversible by cysteine (Robinson & Hall, 1990). On the other hand, lipid-soluble copper complexes such as copper hydroxyquinoline (CuHQO) and copper hydroxyquinaldine (CuHQA), which are able to cross cell membranes (Florence & Stauber, 1986), are highly toxic to this species.…”

Formation, Composition and Physiology of Algal Biofilms

“…Amphora and Amphiprora are both highly resistant to copper (French & Evans, 1988). In Amphora resistance has been attributed to copper immobilization in membrane-bound intracellular bodies, thus keeping cytoplasmic levels low (Daniel & Chamberlain, 1981) and to binding of copper at the cell surface or to mucilage, the latter binding being removed by EDT A or cysteine (Robinson & Hall, 1990). Triorganotins arc lipid soluble compounds and thus rapidly enter cells where they function as energy transfer inhibitors in respiration and photosynthesis (Millner & Evans, 1980).…”