Metallomics and NMR-based metabolomics of Chlorella sp. reveal the synergistic role of copper and cadmium in multi-metal toxicity and oxidative stress

Abstract

Industrial wastewaters often contain high levels of metal mixtures, in which metal mixtures may have synergistic or antagonistic effects on aquatic organisms. A combination of metallomics and nuclear magnetic resonance spectroscopy (NMR)-based metabolomics was employed to understand the consequences of multi-metal systems (Cu, Cd, Pb) on freshwater microalgae. Morphological characterization, cell viability and chlorophyll a determination of metal-spiked Chlorella sp. suggested synergistic effects of Cu and Cd on growth inhibition and toxicity. While Pb has no apparent effect on Chlorella sp. metabolome, a substantial decrease of sucrose, amino acid content and glycerophospholipid precursors in Cu-spiked microalgae revealed Cu-induced oxidative stress. Addition of Cd to Cu-spiked cultures induced more drastic metabolic perturbations, hence we confirmed that Cu and Cd synergistically influenced photosynthesis inhibition, oxidative stress and membrane degradation. Total elemental analysis revealed a significant decrease in K, and an increase in Na, Mg, Zn and Mn concentrations in Cu-spiked cultures. This indicated that Cu is more toxic to Chlorella sp. as compared to Cd or Pb, and the combination of Cu and Cd has a strong synergistic effect on Chlorella sp. oxidative stress induction. Oxidative stress is confirmed by liquid chromatography tandem mass spectrometry analysis, which demonstrated a drastic decrease in the GSH/GSSG ratio solely in Cu-spiked cultures. Interestingly, we observed Cu-facilitated Cd and Pb bioconcentration in Chlorella sp. The absence of phytochelatins and an increment of extracellular polymeric substances (EPS) yields in Cu-spiked cultures suggested that the mode of bioconcentration of Cd and Pb is through adsorption of free metals onto the algal EPS rather than intracellular chelation to phytochelatins.

Leaf anatomical and biochemical adaptations in <em>Typha domingensis</em> Pers. ecotypes for salinity tolerance

“…Environmental stresses, in particular salinity can cause severe loss in turgor in plants and as compensation accumulation of organic osmolytes is a defense mechanism of many plant species (Zhang et al 2015a, Gupta & Huang 2012.…”

Effect of Metals, Metalloids and Metallic Nanoparticles on Microalgae Growth and Industrial Product Biosynthesis: A Review

“…The use of older culture inocullum also improved resistance of Scenedesmus quadricauda against Ag nanoparticles [ 239 ]. Synergistic effects of different heavy metal ions [ 261 ] or metal ions with nanoparticles (see Section 4.2.3 ) on microalgae cells, should be also taken into consideration. Additionally, although nanoparticles can be synthetized by microalgae cells (see Section 3.7 ), the presence of nanoparticles can have negative effects on microalgae ( Table 1 ).…”

Metabolomic Responses of Green Alga Chlamydomonas reinhardtii Exposed to Sublethal Concentrations of Inorganic and Methylmercury

“…11 An increase in amino acid pools under stress conditions has been also reported in sulfur-depleted C. reinhardtii cells 56 and in C. reinhardtii under hyperosmotic stress. 57 However, the present findings for IHg and MeHg are opposite to the decrease of some of the amino acids (lysine, arginine, and glutamine) observed in copper exposure of other green algae Chlorella sp., 58,59 Scenedesmus quadricauda, 60 and diatom Tabellaria flocculosa (Roth) Kuẗzing. 61 Nucleobase/-Tide/-Side Metabolism.…”