Toxicity, Physiological, and Ultrastructural Effects of Arsenic and Cadmium on the Extremophilic Microalga Chlamydomonas acidophila

Silvia Díaz, Patricia De Francisco, Sanna Olsson, Ángeles Aguilera, Elena González-Toril and Ana Martín-González
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Silvia Díaz: Department of Genetics, Physiology and Microbiology, Faculty of Biology, Universidad Complutense de Madrid (UCM), C/José Antonio Novais, 12, 28040 Madrid, Spain
Patricia De Francisco: Department of Genetics, Physiology and Microbiology, Faculty of Biology, Universidad Complutense de Madrid (UCM), C/José Antonio Novais, 12, 28040 Madrid, Spain
Sanna Olsson: Department of Forest Ecology and Genetics, INIA Forest Research Center (INIA-CIFOR), Carretera de A Coruña km 7.5, 28040 Madrid, Spain
Ángeles Aguilera: Astrobiology Center (INTA-CSIC), Carretera de Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
Elena González-Toril: Astrobiology Center (INTA-CSIC), Carretera de Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
Ana Martín-González: Department of Genetics, Physiology and Microbiology, Faculty of Biology, Universidad Complutense de Madrid (UCM), C/José Antonio Novais, 12, 28040 Madrid, Spain

IJERPH, 2020, vol. 17, issue 5, 1-20

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 LC 50 = 1.94 µM. Arsenite was almost four-fold more toxic (LC 50 = 10.91 mM) than arsenate (LC 50 = 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.

Keywords: arsenic; acidophiles; cadmium; cytotoxicity; extremophiles; ultrastructure; ROS (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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