Photosystem I (PSI) is one of the most efficient photoelectric apparatus in nature, converting solar energy into condensed chemical energy with almost 100% quantum efficiency. The ability of PSI to attain such high conversion efficiency depends on the precise spatial arrangement of its protein subunits and binding cofactors. The PSI structures of oxygenic photosynthetic organisms, namely cyanobacteria, eukaryotic algae, and plants, have undergone great variation during their evolution, especially in eukaryotic algae and vascular plants for which light-harvesting complexes (LHCI) developed that surround the PSI core complex. A detailed understanding of the functional and structural properties of this PSI-LHCI is not only an important foundation for understanding the evolution of photosynthetic organisms but is also useful for designing future artificial photochemical devices. Recently, the structures of such PSI-LHCI supercomplexes from red alga, green alga, diatoms, and plants were determined by X-ray crystallography and single-particle cryo-electron microscopy (cryo-EM). These findings provide new insights into the various structural adjustments of PSI, especially with respect to the diversity of peripheral antenna systems arising via evolutionary processes. Here, we review the structural details of the PSI tetramer in cyanobacteria and the PSI-LHCI and PSI-LHCI-LHCII supercomplexes from different algae and plants, and then discuss the diversity of PSI-LHCI in oxygenic photosynthesis organisms.

BACKGROUND: Microalgae biotechnology is considered as a promising way to recover nutrients from centrate wastewater for value-added biomass production, but it is rarely adopted in a real-world application. Current study confirmed that carbon deficiency and suspended solids are two problems jeopardizing the microalgae-based wastewater remediation. In this regard, glycerol was added into centrate wastewater as exogenous carbon source and algal-bacterial cooperation for nutrients recovery assessment. RESULTS:The results showed that glycerol addition increased the biomass yield of algae from 1.54 to 2.58 g L −1 in 5-day culture and, at the same time, improved the removal efficiency of nitrogen and phosphorus, which were further assessed by pilot-scale experiments. Bacterial community analysis indicated that algal-bacterial cooperation involves carbon dioxide and oxygen exchange, phosphorus absorption, and solid organics degradation, forming a complementary nexus beneficial for wastewater treatment.CONCLUSION: Glycerol is proven to be a good carbon source for microalgae growth in the centrate wastewater. Additionally, the cooperation between microalgae and bacteria plays a key role in the nutrients removal during centrate wastewater. It is expected the technology and knowledge provided by current work can further promote the industrialization of microalgaebased wastewater remediation. Figure 6. Scheme for microalgae-based centrate wastewater treatment and mechanism of nutrients recovery. www.soci.org M Xu et al.wileyonlinelibrary.com/jctb

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