Phytochelatins and thiol peptides in freshwater algae in response to metal exposure

Phytochelatins are a class of intracellular metal binding ligands, which are known to be involved in metal detoxification in algae. Previous work in our laboratory (Le Faucheur et al. 2005) has demonstrated that phytochelatins were induced in the freshwater alga Scenedesmus vacuolatus in response to cadmium exposure and that an optimal ratio of thiol groups from the phytochelatins to cadmium was necessary to mitigate toxic effects of Cd. Phytochelatins were also observed in natural periphyton communities and increased at elevated metal concentrations (Le Faucheur et al. 2005 b).

Phytochelatin formation has been further examined as a function of lead(II) in the alga Chlamydomonas reinhardtii (Scheidegger 2010). The formation kinetics indicated that phytochelatins were produced within minutes upon exposure to low concentrations of Pb(II) and that their concentrations increased with time and with increasing Pb(II) concentrations. However, upon long-term exposure (over several days) of the algae to Pb(II), inhibition of algal growth was observed, in spite of phytochelatin production (Scheidegger et al. 2010). The produced phytochelatins were thus not sufficient to prevent Pb(II) toxicity under these conditions. Metal-phytochelatin complexes were also characterized using size-exclusion chromatography and mass spectrometry.

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References

Scheidegger, C., Suter, M. J.-.-F., Behra, R., and Sigg, L., 2012. Characterization of lead-phytochelatin complexes by nano-electrospray ionization mass spectrometry. Frontiers in Microbiology 3, doi: 10.3389/fmicb.2012.00041.

Scheidegger, C., Sigg, L., and Behra, R., 2011. Characterization of lead induced metal-phytochelatin complexes in Chlamydomonas reinhardtii. Environ. Toxicol. Chem. 30, 2546-2552.

Scheidegger, C., Behra, R., and Sigg, L., 2011. Phytochelatin formation kinetics and toxic effects in the freshwater alga C. reinhardtii upon short- and long-term exposure to lead (II). Aquat. Toxicol. 101, 423-429.

Scheidegger, C. (2010) Induction of phytochelatins by lead in the alga Chlamydomonas reinhardtii. PhD thesis ETH Zurich no. 19243.

Le Faucheur, S., Behra, R. and Sigg, L., 2005. Phytochelatin induction, cadmium accumulation and algal sensitivity to free cadmium ions in Scenedesmus vacuolatus. Environ. Toxicol. Chem., 24: 1731-1737.

Le Faucheur, S., Behra, R. and Sigg, L., 2005. Thiol and metal content in periphyton exposed to elevated copper and zinc concentrations : a field and microcosm study. Environ. Sci Technol., 39(20): 8099-8107.

Scheidegger, C. Sigg, L. and Behra, R. Kinetics of phytochelatin synthesis in the green alga C. reinhardtii as function of free lead ions. 18th SETAC Europe, 25. - 29. May 2008, Warsaw.