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Toxicity, physiological, and ultrastructural effects of Arsenic and Cadmium on the extremophilic microalga Chlamydomonas acidophila

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Díaz, Silvia and Francisco Martínez, Patricia de and Olsson, Sanna and Aguilera, Ángeles and González-Toril, Elena and Martín González, Ana María (2020) Toxicity, physiological, and ultrastructural effects of Arsenic and Cadmium on the extremophilic microalga Chlamydomonas acidophila. International Journal of Environmental Research and Public Health, 17 (5). pp. 1-20. ISSN 1661-7827, ESSN: 1660-4601

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Official URL: https://doi.org/10.3390/ijerph17051650



Abstract

The cytotoxicity of cadmium (Cd), arsenate (As(V)), and arsenite (As(III)) on a strain of Chlamydomonas acidophila, isolated from the Rio Tinto, an acidic environment containing high metal(l)oid concentrations, was analyzed. We used a broad array of methods to produce complementary information: cell viability and reactive oxygen species (ROS) generation measures, ultrastructural observations, transmission electron microscopy energy dispersive x-ray microanalysis (TEM–XEDS), and gene expression. This acidophilic microorganism was affected differently by the tested metal/metalloid: It showed high resistance to arsenic while Cd was the most toxic heavy metal, showing an LC50 = 1.94 µM. Arsenite was almost four-fold more toxic (LC50= 10.91 mM) than arsenate (LC50 = 41.63 mM). Assessment of ROS generation indicated that both arsenic oxidation states generate superoxide anions. Ultrastructural analysis of exposed cells revealed that stigma, chloroplast, nucleus, and mitochondria were the main toxicity targets. Intense vacuolization and accumulation of energy reserves (starch deposits and lipid droplets) were observed after treatments. Electron-dense intracellular nanoparticle-like formation appeared in two cellular locations: inside cytoplasmic vacuoles and entrapped into the capsule, around each cell. The chemical nature (Cd or As) of these intracellular deposits was confirmed by TEM–XEDS. Additionally, they also contained an unexpected high content in phosphorous, which might support an essential role of poly-phosphates in metal resistance.


Item Type:Article
Uncontrolled Keywords:Arsenic; Acidophiles; Cadmium; Cytotoxicity; Extremophiles; Ultrastructure; ROS
Subjects:Medical sciences > Biology > Ecology
Medical sciences > Biology > Microbiology
ID Code:60573
Deposited On:19 May 2020 10:50
Last Modified:08 Sep 2020 09:42

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