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High‐molecular‐mass PC complexes (PC‐HMWCs) constituted by phytochelatins (PCs), cadmium and sulfide are synthesized by several organisms after exposure to cadmium. In this study, PC‐HMWCs were isolated from photoheterotrophic Euglena gracilis and purified to homogeneity, resulting in compounds of molecular mass 50–380 kDa depending on the CdCl2 and sulfate concentrations in the culture medium. In contrast with plants and some yeasts, PC‐HMWCs from E. gracilis mainly comprise (57–75%) monothiol molecules (Cys, γ‐glutamylcysteine, GSH) and, to a lesser extent (25–43%), PCs. A similar acid‐soluble thiol compound composition was found in whole cell extracts. The –SH/Cd2+and S2–/Cd2+ ratios found in purified PC‐HMWCs were 1.5 and 1.8, respectively; the (–SH + S2–)/Cd2+ ratio was 3.2. PC‐HMWCs of molecular mass 60 and 100 kDa were also localized inside Percoll‐purified chloroplasts, in which cadmium and PCs were mainly compartmentalized. Cadmium and sulfur‐rich clusters with similar sulfur/cadmium stoichiometries to those of the purified PC‐HMWCs were detected in the chloroplast and throughout the cell by energy dispersive microanalysis and atomic resolution electron microscopy. The presence of PC‐HMWCs in primitive photosynthetic eukaryotes such as the protist, E. gracilis, suggests that their function as the final cadmium‐storage‐inactivation process is widespread. Their particular intracellular localization suggests that chloroplasts may play a major role in the cadmium‐resistance mechanism in organisms lacking a plant‐like vacuole.

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The most efficient system of horizontal subsurface flow constructed wetlands (HSSFCW) for removing dissolved organic carbon (DOC) in the presence of chlorothalonil pesticide (CLT) present in synthetic domestic wastewater was determined using the macrophyte Phragmites australis. Two concentrations of CLT (85 and 385 μg L) and one concentration of glucose (20 mg L) were evaluated in four pilot scale horizontal surface flow constructed wetlands coupled with two sizes of silica gravel, igneous gravel, fine chalky gravel (3.18-6.35 mm), coarse gravel (12.70-25.40 mm) and two water surface heights (20 and 40 cm). For a month, wetlands were acclimated with domestic wastewater. Some groups of bacteria were also identified in the biofilm attached to the gravel. In each treatment periodic samplings were conducted in the influent and effluent. Chlorothalonil was quantified by gas chromatography (GC-ECD m), DOC by an organic carbon analyzer and bacterial groups using conventional microbiology in accordance with Standard Methods. The largest removals of DOC (85.82%-85.31%) were found when using fine gravel (3.18-6.35 mm) and the lower layer of water (20 cm). The bacterial groups quantified in the biofilm were total heterotrophic, revivable heterotrophic, Pseudomonas and total coliforms. The results of this study indicate that fine grain gravel (3.18-6.35 mm) and both water levels (20 to 40 cm) can be used in the removal of organic matter and for the treatment of agricultural effluents contaminated with organo-chloride pesticides like CLT in HSSFCW.