Relationship between Photosynthetic Capacity and Microcystin Production in Toxic Microcystis Aeruginosa under Different Iron Regimes

Abstract

Blooms of harmful cyanobacteria have been observed in various water bodies across the world and some of them can produce intracellular toxins, such as microcystins (MCs), which negatively impact aquatic organisms and human health. Iron participates significantly in cyanobacterial photosynthesis and is proposed to be linked to MC production. Here, the cyanobacteria Microcystis aeruginosa was cultivated under different iron regimes to investigate the relationship between photosynthetic capacity and MC production. The results showed that iron addition increased cell density, cellular protein concentration and the Chl-a (chlorophyll-a) content. Similarly, it can also up–regulate photosynthetic capacity and promote MC–leucine–arginine (MC–LR) production, but not in a dose–dependent manner. Moreover, a significant positive correlation between photosynthetic capacity and MC production was observed, and electron transport parameters were the most important parameters contributing to the variation of intracellular MC–LR concentration revealed by Generalized Additive Model analysis. As the electron transport chain was affected by iron variation, adenosine triphosphate production was inhibited, leading to the alteration of MC synthetase gene expression. Therefore, it is demonstrated that MC production greatly relies on redox status and energy metabolism of photosynthesis in M. aeruginosa. In consequence, more attention should be paid to the involvement of photosynthesis in the regulation of MC production by iron variation in the future.

Interactive Effects of Polyethylene Microplastics and Cadmium on Growth of Microcystis aeruginosa

“…At a molecular level, the synthesis and release of MCs are intricately linked to the transcription levels of relevant genes, the expression of transporter proteins, and the extent of cell membrane damage caused by pollutants [ 36 , 37 , 38 ]. The production of MCs heavily relies on the redox state and energy metabolism of photosynthesis in M. aeruginosa , with the synthesis also associated with reactive oxygen species accumulation, exhibiting an antioxidative stress effect [ 23 ]. Figure 2 reveals that upon the addition of pollutants on day 0, the extracellular MCs content in both the single PE-treated group and the co-treated group was elevated compared to the blank group.…”

“…Algal cells exhibit varying levels of tolerance to different heavy metals. For instance, M. aeruginosa can withstand 50 mg/L Hg 2+ , while Microcystis japonicus shows tolerance concentrations of 0.5 mg/L Cd 2+ and 40 mg/L Pb 2+ [ 22 ], Iron (Fe) has been found to enhance the photosynthesis of M. aeruginosa [ 23 ]. The adsorption capacity of various microplastics for heavy metals varies based on the physicochemical properties of the water environment [ 18 ].…”

Microbiome analysis reveals Microcystis blooms endogenously seeded from benthos within wastewater maturation ponds

“…The ecological role of microcystin biosynthesis by Microcystis species transitioning from sediment hibernation to water column inoculation is complex ( 76 , 77 ). Toxin biosynthesis may fulfil various roles, including allelopathic ( 78 , 79 ), iron chelation ( 80 , 81 ), intra-species communication ( 82 , 83 ), defensive roles ( 84 , 85 ), involvement in photosynthesis ( 86 , 87 ), and adaption to oxidative stress ( 88 , 89 ). The high concentration of intracellular microcystins detected within the in-vitro cyanoHAB propagated using 50% BG-11 suggests that toxin production is linked to nutrient availability and cellular density.…”