Issue 11, 2008

In vivomicrospectroscopy monitoring of chromium effects on the photosynthetic and photoreceptive apparatus of Eudorina unicocca and Chlorella kessleri

Abstract

In microorganisms and plants, chromium (Cr) is not essential for any metabolic process, and can ultimately prove highly deleterious. Due to its widespread industrial use, chromium has become a serious pollutant in diverse environmental settings. The presence of Cr leads to the selection of specific algal populations able to tolerate high levels of Cr compounds. The varying Cr-resistance mechanisms displayed by microorganisms include biosorption, diminished accumulation, precipitation, reduction of Cr6+ to Cr3+, and chromate efflux. In this paper we describe the effects of Cr6+ (the most toxic species) on the photosynthetic and photoreceptive apparatus of two fresh water microalgae, Eudorina unicocca and Chlorella kessleri. We measured the effect of this heavy metal by means of in vivo absorption microspectroscopy of both the thylakoid compartments and the eyespot. The decomposition of the overall absorption spectra in pigment constituents indicates that Cr6+ effects are very different in the two algae. In E. unicocca the metal induced a complete pheophinitization of the chlorophylls and a modification of the carotenoids present in the eyespot after only 120 h of exposition at a concentration equal or greater than 40 µM, which is the limit for total Cr discharge established by US EPA regulations. In C. kessleri, chromium concentrations a hundred times higher than this limit had no effect on the photosynthetic machinery. The different tolerance level of the two algae is suggested to be due to the different properties of the mucilaginous envelope and cell wall covering, respectively, the colonies of Eudorina and the single cells of Chlorella, which binds chromium cations to a different extent.

Graphical abstract: In vivo microspectroscopy monitoring of chromium effects on the photosynthetic and photoreceptive apparatus of Eudorina unicocca and Chlorella kessleri

Article information

Article type
Paper
Submitted
05 Jun 2008
Accepted
20 Aug 2008
First published
18 Sep 2008

J. Environ. Monit., 2008,10, 1313-1318

In vivo microspectroscopy monitoring of chromium effects on the photosynthetic and photoreceptive apparatus of Eudorina unicocca and Chlorella kessleri

A. B. Juarez, L. Barsanti, V. Passarelli, V. Evangelista, N. Vesentini, V. Conforti and P. Gualtieri, J. Environ. Monit., 2008, 10, 1313 DOI: 10.1039/B809566C

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