Effects of Light Intensity and Exposure Period on the Growth and Stress Responses of Two Cyanobacteria Species: <i>Pseudanabaena galeata</i> and <i>Microcystis aeruginosa</i>
2020
Guligena Muhetaer | Takashi Asaeda | Senavirathna M. D. H. Jayasanka | Mahendra B. Baniya | Helayaye D. L. Abeynayaka | M. Harun Rashid | HongYu Yan
Light is an important factor that affects cyanobacterial growth and changes in light can influence their growth and physiology. However, an information gap exists regarding light-induced oxidative stress and the species-specific behavior of cyanobacteria under various light levels. This study was conducted to evaluate the comparative effects of different light intensities on the growth and stress responses of two cyanobacteria species, <i>Pseudanabaena galeata</i> (strain NIES 512) and <i>Microcystis aeruginosa</i> (strain NIES 111), after periods of two and eight days. The cyanobacterial cultures were grown under the following different light intensities: 0, 10, 30, 50, 100, 300, and 600 μmol m<sup>−2</sup> s<sup>−1</sup>. The optical density (OD<sub>730</sub>), chlorophyll a (Chl-a) content, protein content, H<sub>2</sub>O<sub>2</sub> content, and the antioxidative enzyme activities of catalase (CAT) and peroxidase (POD) were measured separately in each cyanobacteria species. <i>P. galeata</i> was negatively affected by light intensities lower than 30 μmol m<sup>−2</sup> s<sup>−1</sup> and higher than 50 μmol m<sup>−2</sup> s<sup>−1</sup>. A range of 30 to 50 μmol m<sup>−2</sup> s<sup>−1</sup> light was favorable for the growth of <i>P. galeata</i>, whereas <i>M. aeruginosa</i> had a higher tolerance for extreme light conditions. The favorable range for <i>M. aeruginosa</i> was 10 to 100 μmol m<sup>−2</sup> s<sup>−1</sup>.
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