Lavoie, Michel; Le Faucheur, Séverine; Fortin, Claude 
ORCID: https://orcid.org/0000-0002-2479-1869 et Campbell, Peter G. C.
(2009).
Cadmium detoxification strategies in two phytoplankton species: Metal binding by newly synthesized thiolated peptides and metal sequestration in granules.
Aquatic Toxicology
, vol. 92
, nº 2.
pp. 65-75.
DOI: 10.1016/j.aquatox.2008.12.007.
Résumé
The aim of this study was to evaluate whether intracellular detoxification mechanisms could explain, at least partially, the different sensitivity to Cd of two freshwater green algae, Chlamydomonas reinhardtii and Pseudokirchneriella subcapitata. Subcellular Cd distribution and the synthesis of metal-binding thiolated peptides were thus examined in both algae exposed to a range of free [Cd2+] from 0.7 to 253 nM. Cadmium partitioning among five subcellular fractions (cellular debris, granules, organelles, heat-denaturable proteins – HDP, and heat-stable proteins – HSP) was determined after differential centrifugation of algal homogenates. Thiolated-peptides, phytochelatins (PCn) and precursors, were analyzed by HPLC with pre-column monobromobimane derivatization. Cadmium accumulation per cell was 2–4 times greater for C. reinhardtii than for P. subcapitata, yet C. reinhardtii was more resistant to Cd with an EC50 of 273 nM Cd2+ [244–333 nM Cd2+ CI95%]) compared to 127 nM Cd2+ [111–143 nM Cd2+ CI95%] for P. subcapitata. Although [Cd] generally increased in the organelle fractions when free [Cd2+] increased in the experimental media, their relative contributions to the total Cd cellular content decreased, suggesting that partial protection of some metal sensitive sites was achieved by the initiation of cellular detoxification mechanisms. An increase in the proportion of Cd in the granules fraction was observed for C. reinhardtii between 6 and 15 nM Cd2+ (i.e., at [Cd2+] < the threshold for growth inhibition) suggesting the involvement of granules in protecting against the occurrence of toxic effects in C. reinhardtii. Both species also produced also high levels of PCn, but with longer oligomers for C. reinhardtii. Unknown thiolated compounds (Xn), which were not canonical or hydroxymethyl PCn, were also found in both algae but at much higher concentrations for C. reinhardtii than for P. subcapitata. This difference in thiol synthesis could also be involved in the higher Cd resistance of C. reinhardtii with respect to P. subcapitata. This study demonstrates the importance of metal detoxification strategies in explaining the Cd sensitivity of different algal species.
| Type de document: | Article |
|---|---|
| Mots-clés libres: | cadmium; algae; subcellular fractionation; thiolated-peptides; phytochelatin; detoxification; granules |
| Centre: | Centre Eau Terre Environnement |
| Date de dépôt: | 09 juill. 2024 17:12 |
| Dernière modification: | 09 juill. 2024 17:12 |
| URI: | https://espace.inrs.ca/id/eprint/15551 |
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