Cytological Studies of Metal Ion Tolerance in the Red Algae <i>Cyanidioschyzon merolae</i>

Abstract

SummaryThe unicellular red alga Cyanidioschyzon merolae is tolerant of high levels of several different metal ions. Cells of the alga cultured with divalent or trivalent metal ions at 10 mM contained elevated concentrations of each metal. The highest tolerance was shown for Al followed by Fe, CuϾNiϾZnϾMn. The viability and morphology of the cells were investigated for different periods of time after metal addition. In contrast to land plants, C. merolae exhibited a very high tolerance to metal ions, but the response varied according to the metal ion added. In particular, Mn, Zn and Ni ions affected the structure and function of the chloroplast, and markedly reduced the cell viability. Nevertheless, the tolerance of C. merolae to metal ions is the highest among reported eukaryotic cells. Cellular mechanisms for detoxification or defense against metal ions must be well developed in this alga.

Molecular mechanisms of heavy metal adaptation of an extremophilic red algaCyanidioschyzon merolae

“…2) confirming the long-term metabolic adaptability of C. merolae to such high Ni concentrations. The cell survivability data is in contrast with the work by Misumi et al, (2008) who observed up to 20% viability of C. merolae cells upon 10 mM Ni treatment on day 70, measured as autofluorescence of the chloroplast. In the latter work, the experimental and culture conditions were considerably different, as a different Ni source was used (Ni(NO 3 ) 2 instead of NiSO 4 ); growth pH was slightly lower (2.3 compared to 2.5 in this work) and the final cell suspension volume was also different (50 versus 125 mL in this work), all of which may affect the effective toxicity of Ni in the cells.…”

“…In the latter work, the experimental and culture conditions were considerably different, as a different Ni source was used (Ni(NO 3 ) 2 instead of NiSO 4 ); growth pH was slightly lower (2.3 compared to 2.5 in this work) and the final cell suspension volume was also different (50 versus 125 mL in this work), all of which may affect the effective toxicity of Ni in the cells. Moreover, in Misumi et al, (2008), the starting OD of the culture is not specified. In the present study, the starting OD 750 was ∼0.150 at 750 nm, which could have caused much higher total effective toxicity of Ni compared to the work by Misumi and colleagues (2008).…”

“…Moreover, in Misumi et al, (2008), the starting OD of the culture is not specified. In the present study, the starting OD 750 was ∼0.150 at 750 nm, which could have caused much higher total effective toxicity of Ni compared to the work by Misumi and colleagues (2008).…”

Revised classification of the Cyanidiophyceae based on plastid genome data with descriptions of the Cavernulicolales ord. nov. and Galdieriales ord. nov. (Rhodophyta)

“…The Cyanidiophyceae, one of seven red algal classes, contains well-known extremophiles. Most species occur in environments with high temperatures (45-65°C) and acidic environments (pH 0.5-3.0), and they are sometimes found where there are high concentrations of heavy metals (Beardall & Entwisle, 1984;Enami et al, 2010;Minoda et al, 2015;Misumi et al, 2008;Nagasaka et al, 2002Nagasaka et al, , 2004. Therefore, Cyanidiophyceae occur worldwide in diverse volcanic sites, hot springs, hydrothermal pits, mines, and acidic swamps (Barcyte et al, 2018;Ciniglia et al, 2004;Toplin et al, 2008).…”

Cultivation of Acidophilic Algae Galdieria sulphuraria and Pseudochlorella sp. YKT1 in Media Derived from Acidic Hot Springs

“…In addition, the Cyanidiophyceae are tolerant to heavy metals and absorb high concentrations of them from an aquatic environment (Nagasaka et al, 2004; Misumi et al, 2008). This is because metals are easily ionized and dissolved in acidic water.…”