Oxidative Stress and Antioxidant Responses of Phormidium ambiguum and Microcystis aeruginosa Under Diurnally Varying Light Conditions

Abstract

Two harmful cyanobacteria species (Phormidium ambiguum and Microcystis aeruginosa) were exposed to diurnal light-intensity variation to investigate their favorable and stressed phases during a single day. The photosynthetically active radiation (PAR) started at 0 µmol·m−2·s−1 (06:00 h), increased by ~25 µmol·m−2·s−1 or ~50 µmol·m−2·s−1 every 30 min, peaking at 300 µmol·m−2·s−1 or 600 µmol·m−2·s−1 (12:00 h), and then decreased to 0 µmol·m−2·s−1 (by 18:00 h). The H2O2 and antioxidant activities were paralleled to light intensity. Higher H2O2 and antioxidant levels (guaiacol peroxidase, catalase (CAT), and superoxidase dismutase) were observed at 600 µmol·m−2·s−1 rather than at 300 µmol·m−2·s−1. Changes in antioxidant levels under each light condition differed between the species. Significant correlations were observed between antioxidant activities and H2O2 contents for both species, except for the CAT activity of P. ambiguum at 300 µmol·m−2·s−1. Under each of the conditions, both species responded proportionately to oxidative stress. Even under maximum light intensities (300 µmol·m−2·s−1 or 600 µmol·m−2·s−1 PAR intensity), neither species was stressed. Studies using extended exposure durations are warranted to better understand the growth performance and long-term physiological responses of both species.

Haematococcus lacustris Carotenogensis: A Historical Event of Primary to Secondary Adaptations to Earth’s Oxygenation

“…As a representative, H. lacustris accumulated the maximum astaxanthin under oxidative stress, e.g., treatments of high light and FeSO 4 + SA, ~54.3% of total astaxanthin [19]. High light-induced oxidative stress is among the strongest inducers for secondary carotenoids in a wide range of photosynthetic organisms, from green algae to higher plants [50,51]. Effective oxidative adaptation has been widely preserved in oxygenic photosynthetic organisms during Earth's oxygenation.…”

Temporal variation of 2‐MIB and geosmin production by Pseudanabaena galeata and Phormidium ambiguum exposed to high‐intensity light

“…When the bubbling, mechanical mixing, and reservoir drawdown‐like techniques are employed, cyanobacteria are subjected to undesirable light and temperature regimes via mixing the water layers or reducing the water depth. Notably, both low and high light intensities can negatively affect the growth of cyanobacteria (Hsieh et al, 2014; Muhetaer, Senavirathna, & Fujino, 2020). When direct sunlight is used, the light intensity can reach 1500 μmol m −2 s −1 photosynthetically active radiation (PAR) intensity.…”

Recoverability of Microcystis aeruginosa and Pseudanabaena foetida Exposed to a Year-Long Dark Treatment

“…As pivotal primary producers and pioneer species, they exhibit outstanding stress resilience [3]. Scientists have conducted numerous simulations on the response of cyanobacteria to extreme conditions, including polar regions [4], space radiation [5,6], a high-chlorine salt environment in the surface of Mars [7], Martian-like pure CO 2 atmosphere conditions [8], high temperature [5], and high light [9], in anticipation that it can become a pioneer species to transform outer planets and reserve bioenergy during disasters. Studies have demonstrated that cyanobacteria, especially Microcystis aeruginosa, survive in extreme environments, although oxidative stress is produced [10,11].…”