Cadmium toxicity on the freshwater microalga Chlamydomonas moewusii Gerloff: Biosynthesis of thiol compounds

Abstract

Cadmium (Cd) toxicity and production of different thiols (phytochelatins, glutathione, gamma-Glu-Cys and cysteine) were studied in the microalga Chlamydomonas moewusii exposed to different concentrations of this metal (1, 2, 4, 6, 8, and 10 mg/L) for 96 h. The inhibitory effect of Cd on growth was demonstrated. The value of EC50 (metal concentration which reduces the population growth to 50% of the control) obtained for this microalga was estimated at 4.1 +/- 0.8 mg/L of Cd after 96 h of exposure. The amount of thiol compounds synthesized by C. moewusii changed with Cd concentration. Cysteine concentrations were significantly higher compared to those of gamma-Glu-Cys and glutathione in all the Cd concentrations assayed. The amino acid cysteine reached its higher levels in those cultures in which a decrease in the concentration of phytochelatins (PCs) was observed. Both cysteine and glutathione concentrations showed significant differences along the Cd concentrations assayed, while the amount of gamma-Glu-Cys detected remained stable. The PCs detected were of two, three, and four subunits. The level of PC(2) was higher than that of PC(3) and PC(4). PC(4) was detected only in the cultures exposed to the Cd concentrations of 1 and 2 mg/L, in which the synthesis of phytochelatins was higher. A rapid increase in the production of PC(2) and PC(3) was observed up to a Cd concentration of 2 mg/L, after which their levels began to decrease. Phytochelatins were not detected in cultures without Cd (controls) and in those exposed to the maximum Cd concentration (10 mg/L), in which cell growth was completely inhibited.

Physiological characterization of cadmium‐exposed Chlamydomonas reinhardtii

“…Such discrepancies could be explained, for example, by different strains and sometimes even mutant strains, different cultivation conditions or different intracellular metal concentrations. A dose-dependent reaction of the cysteine towards cadmium was shown before for Chlamydomonas moewusii (Suárez et al 2010). Thus, intracellular metal concentration has to be specified in each study to compare the results.…”

Effects of sodium sulfate on the freshwater microalgaChlamydomonas moewusii: implications for the optimization of algal culture media

“…C. moewusii is a microalga widely used as a model organism for many studies in biology, for example, toxicological studies (Suárez et al. , Mera et al. ), flagellar structure (Jones and Lewin ), studies with chloroplasts (Richard et al.…”

“…Kinetic equations, which describe the growth in relation to a nutrient, are important in understanding many phenomena in biotechnological and ecological processes. C. moewusii is a microalga widely used as a model organism for many studies in biology, for example, toxicological studies (Su arez et al 2010, Mera et al 2014, flagellar structure (Jones and Lewin 1960), studies with chloroplasts (Richard et al 1994), biosynthesis of metabolites , biotransformation (Otto et al 2015), and genetic studies (Bussieres et al 1996).…”

Sensing the dynamics of oxidative stress using enhanced absorption in protein-loaded random media

“…In addition to its environmental importance, the completion of the C. reinhardtii genome project revealed this microorganism as a useful model to investigate molecular cellular processes20. Cadmium is a widespread environmental toxicant known to cause adverse effects in algae, including growth and chlorophyll synthesis inhibition2122, increase in the superoxide dismutase activity23, phytochelatine induction21, and oxidative stress2324. C. reinhardtii homeostasis and tolerance to Cd(II) are well documented and the following chronological lethal sequence has been reported: oxidative stress, lipid and nucleic acid peroxidation, cell structure alteration, mutagenesis and apoptosis25.…”