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EFFECT OF ELEVATED TEMPERATURE, DARKNESS, AND HYDROGEN PEROXIDE TREATMENT ON OXIDATIVE STRESS AND CELL DEATH IN THE BLOOM-FORMING TOXIC CYANOBACTERIUM MICROCYSTIS AERUGINOSA1
Article first published online: 4 NOV 2011
© 2011 Phycological Society of America
Journal of Phycology
Volume 47, Issue 6, pages 1316–1325, December 2011
How to Cite
Bouchard, J. N. and Purdie, D. A. (2011), EFFECT OF ELEVATED TEMPERATURE, DARKNESS, AND HYDROGEN PEROXIDE TREATMENT ON OXIDATIVE STRESS AND CELL DEATH IN THE BLOOM-FORMING TOXIC CYANOBACTERIUM MICROCYSTIS AERUGINOSA. Journal of Phycology, 47: 1316–1325. doi: 10.1111/j.1529-8817.2011.01074.x
Received 10 December 2010. Accepted 03 May 2011.
- Issue published online: 1 DEC 2011
- Article first published online: 4 NOV 2011
- caspase 3–like activity;
- cell death;
- DNA degradation;
- hydrogen peroxide;
- Microcystis aeruginosa;
- oxidative stress;
- terminal deoxynucletidyl transferase-mediated dUTP nick end labeling
This study assessed the implication of oxidative stress in the mortality of cells of Microcystis aeruginosa Kütz. Cultures grown at 25°C were exposed to 32°C, darkness, and hydrogen peroxide (0.5 mM) for 96 h. The cellular abundance, chl a concentration and content, maximum photochemical efficiency of PSII (Fv/Fm ratio), intracellular oxidative stress (determined with dihydrorhodamine 123 [DHR]), cell mortality (revealed by SYTOX-labeling of DNA), and activation of caspase 3–like proteins were assessed every 24 h. The presence of DNA degradation in cells of M. aeruginosa was also assessed using a terminal deoxynucletidyl transferase-mediated dUTP nick end labeling (TUNEL) assay at 96 h. Transferring cultures from 25°C to 32°C was generally beneficial to the cells. The cellular abundance and chl a concentration increased, and the mortality remained low (except for a transient burst at 72 h) as did the oxidative stress. In darkness, cells did not divide, and the Fv/Fm continuously decreased with time. The slow increase in intracellular oxidative stress coincided with the activation of caspase 3–like proteins and a 15% and 17% increase in mortality and TUNEL-positive cells, respectively. Exposure to hydrogen peroxide had the most detrimental effect on cells as growth ceased and the Fv/Fm declined to near zero in less than 24 h. The 2-fold increase in oxidative stress matched the activation of caspase 3–like proteins and a 40% and 37% increase in mortality and TUNEL-positive cells, respectively. These results demonstrate the implication of oxidative stress in the stress response and mortality of M. aeruginosa.