Oxidative stress in the cyanobacterium Microcystis aeruginosa PCC 7813: Comparison of different analytical cell stress detection assays

Comparison of UV-A photolytic and UV/TiO2 photocatalytic effects on Microcystis aeruginosa PCC7813 and four microcystin analogues: A pilot scale study

“…The photosynthetic activity decrease observed during photolysis corresponds to the decrease in the cell number observed until day 3 (Figure 1A). As previously reported by Menezes et al (2020), photosynthetic activity measurements showed a faster response to cell damage than cell density measurements, indicating that cell stress occurred as early as 24 hours before cell density changes could be observed by cell density measurements. The cell stress results from day 3 are most likely due to the very low cell density observed from that point in time (5 x 10 5 cells mL -1 ), which were lower than the minimum concentration of cells required for cell stress determination.…”

“…A Mini-PAM system (Walz, Germany) was used for cyanobacterial photosynthetic activity analysis according to Menezes et al (2020). In short, the minimal fluorescence F0 was measured by adding 400 µL of sample into a cuvette under agitation followed by diuron (0.5 M) addition (20 µL) and the true maximal fluorescence measurement (FM') by a saturating pulse under actinic light.…”

“…Direct photolysis and the indirect oxidation by extracellular reactive oxygen species (ROS) initially cause cellular stress and then damage to the cell membrane, without promoting the complete destruction of the cell (Ou et al 2011a(Ou et al , 2011b. Photosynthetic activity as expressed as the FV/FM' ratio is a rapid method that can represent the level of stress and/or damage in cyanobacterial cells (Menezes et al, 2020;Stirbet et al, 2018;Yang et al, 2013). Cyanobacterial stress causes a decline in the FV/FM' ratio, which means that the lower the FV/FM' ratio (photosynthetic activity) the more damage or stress there is to the cyanobacteria.…”

Loss of 2‐Cys‐Prx affects cellular ultrastructure, disturbs redox poise and impairs photosynthesis in cyanobacteria

“…Interestingly, in a manner similar to An-KD4641, the phycocyanin-depleted Synechocystis PCC 6803 cpcF mutant also showed considerably reduced growth, indicating impaired photosynthetic capabilities. Indeed, photosynthesis is one of the first physiological processes to be adversely affected by oxidative stress in cyanobacteria (Menezes et al, 2021). Oxidising agents such as H 2 O 2 are also known to inhibit repair of photodamage to the photosynthetic machinery (Murata & Nishiyama, 2018).…”

In Situ H2o2 Treatment of Blue-Green Algae Contaminated Reservoirs Causes Significant Improvement in Drinking Water Treatability

“…The use of H 2 O 2 for in-reservoir treatment, in addition to reducing cyanobacteria densities, can also improve other limnological parameters important to water treatment processes such as turbidity, color, dissolved and particulate organic matter, and pH (Menezes et al, 2021;Patki et al, 2021). However, due to the complex nature of monitoring and interpreting the magnitude of H 2 O 2 efficiency on parameters important to water treatability only few studies tackled this topic (Varol, 2020).…”