IngentaConnect Metal metabolism in the red alga Cyanidium caldarium and its rela...

Authors: Nagasaka S.¹; Nishizawa N.K.²; Mori S.¹; Yoshimura E.³

Source: BioMetals, Volume 17, Number 2, April 2004 , pp. 177-181(5)

Publisher: Springer

Abstract:

The unicellular red alga Cyanidium caldarium is tolerant to high levels of various metal ions. Cells of this alga cultured with divalent metal ions at 5 mM contained an elevated concentration of each metal, with the highest level for Zn followed by Mn > Ni > Cu. This order is in fair agreement with the toxicity levels reported previously, with the exception of Mn, which shows a toxicity level comparable to that of Ni. Transmission electron microscopy indicated the presence of electron-dense bodies in the algal cells, and elemental analysis by energy dispersive X-ray spectrometry showed high levels of Fe and P in these bodies. Accumulation of Zn was found in these particles in Zn-treated algal cells, whereas no such deposition was found for Cu, Ni, or Mn in cells treated with the respective metals. Although trapping of Zn in the intracellular bodies may contribute to reduction of metal activity in the cells, this effect can be overcome by high intracellular levels of Zn that result in a high degree of toxicity. The correlation between intracellular concentration and toxic levels of metal ions implies that the reduced incorporation of the metals is a major detoxification mechanism in this alga.

Keywords: Cyanidium caldarium; EDX; ESR; heavy metal

Document Type: Research article

DOI: 10.1023/B:BIOM.0000018403.37716.ff

Affiliations: 1: Department of Applied Biological Chemistry, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan 2: Global Agricultural Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation, 2-1-6 Sengen, Tsukuba 305-0047, Japan 3: Department of Applied Biological Chemistry, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Tel and, Fax: +81-3-5841-5155, Email: ayoshim@mail.ecc.u-tokyo.ac.jp

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Metal metabolism in the red alga Cyanidium caldarium and its relationship to metal tolerance