Assessing thallium phycoremediation by applying <i>Anabaena laxa</i> and <i>Nostoc muscorum</i> and exploring its effect on cellular growth, antioxidant, and metabolic profile

Abstract

Thallium (Tl), a key element in high-tech industries, is recognized as a priority pollutant by the US EPA and EC. Tl accumulation threatens aquatic ecosystems. Despite its toxicity, little is known about its impact on cyanobacteria. This study explores the biochemical mechanisms of Tl(I) toxicity in cyanobacteria, focusing on physiology, metabolism, oxidative damage, and antioxidant responses. To this end, <i>Anabaena</i> and <i>Nostoc</i> were exposed to 400 µg/L, and 800 µg/L of Tl(I) over seven days. <i>Anabaena</i> showed superior Tl(I) accumulation with 7.8% removal at 400 µg/L and 9.5% at 800 µg/L, while <i>Nostoc</i> removed 2.2% and 7.4%, respectively. Tl(I) exposure significantly reduced the photosynthesis rate and function, more than in <i>Nostoc</i>. It also altered primary metabolism, increasing sugar levels and led to higher amino and fatty acids levels. While Tl(I) induced cellular damage in both species, <i>Anabaena</i> was less affected. Both species enhanced their antioxidant defense systems, with <i>Anabaena</i> showing a 175.6% increase in SOD levels under a high Tl(I) dose. This suggests that <i>Anabaena's</i> robust biosorption and antioxidant systems could be effective for Tl(I) removal. The study improves our understanding of Tl(I) toxicity, tolerance, and phycoremediation in cyanobacteria, aiding future bioremediation strategies.