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Updated: May 9, 2026

Laboratory Simulation of an Iron(II)-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria
Published on: July 24, 2016
Iron bioavailability as a critical "switch" governing microbial metabolic function and cross-species cooperation for
Jiawei Fan1, Bing Zhang1, Yuchen An1
1Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400044, China; College of Environment and Ecology, Chongqing University, Chongqing 400044, China.
None:
Filamentous cyanobacteria are recognized as the primary architects of hydrostatically formed photogranules (HSP), an emerging nature-based technology for sustainable wastewater treatment. However, the underlying mechanism of cyanobacteria-driven photogranulation regulated by environmental factors remains poorly understood. Given the dual effects of light and iron on cyanobacterial physiology, this study elucidated the cause-and-effect relationship between light-induced iron bioavailability and HSP development. Results revealed that light intensity governed iron bioavailability through photochemical and biological pathways. Compared to low light intensity (65 µmol/m2·s), high light intensity (260 µmol/m2·s) promoted iron redistribution from mineral phases to extracellular polymeric substances (EPS), thereby increasing the pool of bioavailable iron. EPS-bound iron (FeEPS) exhibited strong positive correlations with cyanobacterial proliferation (R > 0.93) and EPS secretion (R > 0.88) at high irradiance, accompanied by accelerated photogranulation. Multi-omics profiling uncovered that high light intensity activated siderophore-mediated iron acquisition and iron-dependent metabolic pathways, including photosynthetic electron transport, energy metabolism, and EPS biosynthesis. Moreover, the metabolic complementarity between cyanobacteria and Pseudomonas-affiliated bacteria via cross-species exchange of siderophores and vitamins, further facilitated intracellular iron accumulation and photogranulation under high light intensity. Collectively, this study reveals that high light intensity not only selectively promoted cyanobacteria growth but also reshaped iron bioavailability, which functioned as a critical "switch" controlling microbial metabolism and cross-species cooperation for photogranulation.
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