Effects of Metal Combinations on the Production of Phytochelatins and Glutathione by the Marine Diatom Phaeodactylum tricornutum |
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Authors: | Silvia K Kawakami Martha Gledhill Eric P Achterberg |
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Institution: | (1) School of Earth, Ocean and Environmental Science, University of Plymouth, Plymouth, PL4 8AA, UK;(2) School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, Southampton, SO14 3ZH, UK |
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Abstract: | Copper, Cd and Zn can be found at elevated concentrations in contaminated estuarine and coastal waters and have potential
toxic effects on phytoplankton species. In this study, the effects of these metals on the intracellular production of the
polypeptides phytochelatin and glutathione by the marine diatom Phaeodactylum tricornutum were examined in laboratory cultures. Single additions of Cu and Cd (0.4 μM Cu2 and 0.45 μM Cd2+) to the culture medium induced the production of short-chained phytochelatins ((γ-Glu-Cys)n-Gly where n = 2–5), whereas a single addition of Zn (2.2 μM Zn2+) did not stimulate phytochelatin production. Combination of Zn with Cu resulted in a similar phytochelatin production compared
with a single Cu addition. The simultaneous exposure to Zn and Cd led to an antagonistic effect on phytochelatin production,
which was probably caused by metal competition for cellular binding sites. Glutathione concentrations were affected only upon
exposure to Cd (85% increase) or the combination of Cd with Zn (65% decrease), relative to the control experiment. Ratios
of phytochelatins to glutathione indicated a pronounced metal stress in response to exposures to Cu or Cd combined with Zn.
This study indicates that variabilities in phytochelatin and glutathione production in the field can be explained in part
by metal competition for cellular binding sites. |
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Keywords: | glutathione metal toxicity metal stress Phaeodactylum tricornutum phytochelatins thiols |
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