A comparative study of the accumulation and detoxification of copper and zinc in Chlamydomonas reinhardtii: The role of extracellular polymeric substances

Characterization of polyphenols and carbohydrates exuded by Phaeodactylum tricornutum diatom grown under Cu stress

“…Our results agree with those of Tonietto et al, who found that carbohydrates were the main components of the exudates of the cyanobateria Cylindrospermopsis raciborskii and were strongly correlated with the ligand concentration for Cu (R = 0.997) 48 , concluding that a high diversity of ligands increases the metal buffering capacity of the medium and thus, enhances the tolerance of the biota to metal toxicity. Li et al also reported increases in extracellular polysaccharides exuded by C. reinhardtii under Cu toxicity conditions 1 , with polysaccharides being the main substances bound to Cu on the cell surface , and enhanced sorption of C. reinhardtii cells with increasing Cu concentration. In addition, a significant correlation of extracellular polysaccharides, proteins and DNA with Cu accumulation was found.…”

“…Our results agree with those reported by López et al 10 , who found that marine microalgae Dunaliella tertiolecta grown in the presence of high levels of Cu exuded most of the polyphenols into the medium to alleviate Cu toxicity. Li et al 1 studied Cu and Zn accumulation and detoxification strategies in the freshwater green microalga Chlamydomonas reinhardtii ( C. reinhardtii ), showing that extracellular matter played a major role in Cu sorption and resistance, which was not observed in the Zn tolerance strategy, where extracellular substances played a minor role.…”

“…Diatoms have multiple mechanisms to fight against metal toxicity inside the cell, such as gene regulation, chelation, transport into compartments, vacuoles or other organelles, causing heavy metal immobilization, etc. 37 – 40 , but only exuded and cell wall-associated compounds seem to participate in detoxification mechanisms externally 1 . Therefore, the differences observed in phenolic profiles appear to be the cellular response to different requirements for survival inside and outside of Cu-exposed diatoms.…”

“…Marine microorganisms are known to release organic ligands that can regulate and modify the speciation of trace metals in the surrounding environment, affecting the bioavailability of these trace metals needed in a vast array of enzymatic reactions, and their potential toxicity 1 – 3 . Thus, chemical speciation may aid biosorption capacity and cellular uptake of metals in regions of low concentration and hinder toxicity in the presence of high concentration 4 .…”

Adsorption of Sodium Ions by Exopolysaccharides from Pseudomonas simiae MHR6 and Its Improvement of Na+/K+ Homeostasis in Maize under Salt Stress

“…The production of EPS is one of the main responses of bacteria to various environmental stresses. 26 Polysaccharides and proteins are the two main components of EPS, which can induce significant stress responses under constant stimulation of NaCl. As shown in Figure 2, NaCl treatment significantly affected EPS secretion and composition.…”