Responses to sublethal copper exposure in two strains of Chlamydomonas reinhardtii (Volvocales, Chlorophyceae) in autotrophic and mixotrophic conditions.

SABATINI SEBASTIAN; LEONARDI PATRICIA,; RODRIGUEZ CECILIA

PHYCOLOGIA

INT PHYCOLOGICAL SOC

Lugar: Japón; Año: 2011 vol. 50 p. 78 - 88

0031-8884

The aim of this work was to determine the responses to sublethal copper exposure (20 and 40 mM CuCl2) in two Chlamydomonas reinhardtii strains: the wild type 4A+ and the pleiotropic mutant cur9, originally selected as a coppertolerant phenotype in mixotrophic conditions. Bioassays were performed in both autotrophic and mixotrophic media, under low irradiation (50 mmol m22 s21). At the onset, Cu2+ concentration in culture media was estimated by MINEQL software. Oxidative stress indicators, such as changes in photosynthetic pigment ratios, catalase activity, concentration of thiobarbituric acid reactive substances (TBARS) and growth rate, demonstrated a better performance of the wild type and the mutant strain in autotrophic and mixotrophic conditions, respectively. Moderate oxidative stress was accompanied by ultrastructural changes, such as accumulation of starch and vacuoles with electronic-dense deposits and membranous structures together with mild thylakoidal and mitochondrial crest disorganization. In mixotrophic conditions isocitrate lyase (ICL) activity peaked after 72 h incubation. An inverse relation between catalase and ICL activities was verified and proved to be a good indicator of oxidative stress correlating consistently with other characteristic features such as depression in growth rate or increase in TBARS dosage. mM CuCl2) in two Chlamydomonas reinhardtii strains: the wild type 4A+ and the pleiotropic mutant cur9, originally selected as a coppertolerant phenotype in mixotrophic conditions. Bioassays were performed in both autotrophic and mixotrophic media, under low irradiation (50 mmol m22 s21). At the onset, Cu2+ concentration in culture media was estimated by MINEQL software. Oxidative stress indicators, such as changes in photosynthetic pigment ratios, catalase activity, concentration of thiobarbituric acid reactive substances (TBARS) and growth rate, demonstrated a better performance of the wild type and the mutant strain in autotrophic and mixotrophic conditions, respectively. Moderate oxidative stress was accompanied by ultrastructural changes, such as accumulation of starch and vacuoles with electronic-dense deposits and membranous structures together with mild thylakoidal and mitochondrial crest disorganization. In mixotrophic conditions isocitrate lyase (ICL) activity peaked after 72 h incubation. An inverse relation between catalase and ICL activities was verified and proved to be a good indicator of oxidative stress correlating consistently with other characteristic features such as depression in growth rate or increase in TBARS dosage.