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The influence of selenite on growth and antioxidative response in green microalga Monoraphidium cf. contortum

Selenium (Se) is a trace element that appears in nature in different organic and inorganic forms. It affects organisms in a dosage-related manner being essential at low and toxic at higher concentrations, depending on its chemical form and different environmental factors. Potential toxicity lies in the ability of Se uptake and biotransformation by primary producers, particularly microalgae, and subsequent transport along the aquatic food chains. This study aimed to determine the antioxidative status of unicellular green microalga Monoraphidium cf. contortum during 24-72 h in vitro exposure to sodium selenite (5, 25, 50 and 100 mg/L). The results showed the inhibiting effect of higher selenite concentrations on algal growth, reduced content of photosynthetic pigments and enhanced generation of reactive oxygen species (ROS) and lipid peroxidation products compared to control cultures. Selenite treatment increased the content of total soluble phenols and decreased the total glutathione concentration. Also, selenite increased the activities of antioxidative enzymes glutathione S- transferase, glutathione reductase, glutathione peroxidase and ascorbate peroxidase, but inhibited the activity of catalase in algal cells. Treatment with the lowest selenite concentration had a positive effect on algal growth and reduced the total ROS levels. Therefore, due to both, pro-oxidant and antioxidant action of Se in green microalgae, toxicological and nutritional aspects deriving from its bioaccumulation and transformation into organic forms should be further evaluated. This is important in the context of high Se tolerance in algae and their role in its cycling and transfer to higher trophic levels.

green microalgae, algal cultures, selenium, antioxidants, glutathione

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