npj Biological Timing and Sleep - From phenomenon to mechanism in the circadian clock of Synechococcus elongatus

Human immunodeficiency virus type 1 (HIV-1) remains a major global public health challenge due to lifelong persistence, latency, and the emergence of drug resistance. Natural bioactive compounds are i...

Diflavin-linked disulfide oxidoreductase (DDOR) from the cyanobacterium Synechocystis sp. PCC6803 is an NADPH-thioredoxin reductase (NTR) superfamily enzyme that forms a homodimer containing two FAD molecules (FAD1 and FAD2) per monomer. FAD1 is conserved in the NTR superfamily, while FAD2 is characteristic of DDOR. Under aerobic conditions, thiol reduction of DDOR produces an apparently air-stable neutral blue semiquinone, but the respective roles of FAD1 and FAD2 in the reduction process remain unclear. To address this, spectroscopic, structural and mutational analyses were performed to investigate the contributions of the two FAD molecules. Recombinant apo- and holo-DDOR synthesised in Escherichia coli cells were separated and purified. Fluorescence titration of the apo-DDOR with FAD revealed rapid binding of two FADs. Stopped-flow analysis indicated biphasic binding of FAD to apo-DDOR. X-ray crystal structures of apo- and holo-DDORs exhibited pronounced conformational differences in the FAD-binding sites, suggesting that the first FAD may bind to the FAD1-binding site and subsequently induce formation of the FAD2-binding site. Systematic replacement of amino acid residues in the FAD2-binding site showed that mutations at the characteristic loop region bearing the GKKDSLY motif resulted in binding of three flavin species of FAD, flavin mononucleotide and riboflavin. Moreover, replacement of both Trp53 and Tyr143 at the binding site of the isoalloxazine ring of FAD2 with Ala residues yielded exclusively the apo-form. These results indicate that the loop region restricts the flavin species bound at the FAD2-binding site, and Trp53 and Tyr143 are important for FAD binding to both the FAD1- and FAD2-binding sites.

Meiyu is a persistent rainy weather phenomenon in East Asia caused by a subtropical monsoon front. Under global climate change, the intensity and extr…

Despite the great diversity of the phylum Chordata, lifelong obligate symbiosis with cyanobacteria is only known in certain species belonging to four genera of didemnid ascidians: Didemnum, Diplosoma,...

Ferredoxins are small FeS cluster-containing proteins that play a central role in distributing electrons within the cell. The cyanobacterium Synechocystis sp. PCC 6803 contains several ferredoxin iso....

Abstract. The widespread oceanic cyanobacterial Prochlorococcus genus is a major contributor to global carbon fixation, yet mechanisms enabling this lineag

As an experienced Senior Marine Ecologist at Wageningen Marine Research (WMR) in Yerseke, you will lead a team of dedicated researchers who are working together on a range of ecologically relevant iss...

Abstract. The widespread oceanic cyanobacterial Prochlorococcus genus is a major contributor to global carbon fixation, yet mechanisms enabling this lineag

Microcystis aeruginosa is a bloom-forming cyanobacterium widely distributed in eutrophic freshwater systems. Most strains are blue–green due to the presence of the photosynthetic pigments phycocyanin ...

Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans...

Viruses encode ribosomal proteins (RPs), but their genomes usually harbor a single RP-coding gene. Here, we reannotate the genome of the jumbo cyanophage PhiMa05 and show that it encodes six RPs, an R...

Synechococcus elongatus PCC 7942 is a widely used model cyanobacterium for diverse research fields and for bioproduction applications owing to its ease of cultivation, genetic modification, and abili...

Abstract. Antibiotic pollution poses increasing risks to freshwater ecosystems, yet its effects on phytoplankton competition, particularly cyanobacterial s

Despite the biotechnological potential of cyanobacteria, the antibacterial, antifungal, and prebiotic properties of the genus Calothrix remain largely unexplored. This study characterizes the composit...

Examining the coordination of the O2-sensitive N2 fixation process with photosynthesis at single-cell level in the filamentous Trichodesmium, we find spatio-temporal separation of N2 fixation and pho....

The cyanobacterial circadian clock is driven by a core post-translational oscillator composed of KaiA, KaiB, and KaiC, with the histidine kinase (HK), SasA, acting as the primary transducer of timing...

The Nostocales are filamentous cyanobacteria that include bloom-forming, nitrogen-fixing species with major ecological and biotechnological relevance. Owing to their metabolic diversity, nitrogen-fixing capabilities and nutritional profile, they hold potential for various biotechnological applications including the production of nutraceuticals and biofertilizers. However, the capacity of certain Nostocales species to produce cyanotoxins also raises health concerns. This study provides a comparative bioinformatic analysis of 161 Nostocales genomes from the National Center for Biotechnology Information (NCBI) and three newly sequenced Aphanizomenon flos-aquae (AFA) strains, including Klamath AFA, with a focus on taxonomy, cyanotoxin-associated biosynthetic gene clusters (BGCs), natural competence, restriction-modification systems and vitamin B12 metabolism. Our analysis supports reassessment of several AFA-labelled genomes and refines the boundaries of the core AFA cluster. Cyanotoxin-associated BGCs, specifically for anatoxin-a, saxitoxin, cylindrospermopsin and microcystin/nodularin, were detected in only 7.3% of the genomes. Natural competence genes required for horizontal gene transfer were found in 89.6% of the genomes, although the presence of multiple restriction-modification system-associated proteins in Nostocales species, especially Aphanizomenon, Anabaena, Dolichospermum and Nostoc sp. may limit foreign gene acquisition. Additionally, ~30% of the genomes harbour a shared btu operon arrangement associated with B12 import, observed here across multiple Nostocales genera. B12 content in the AFA strains was measured at ~0.4–0.5 µg g−1 dry biomass and is likely linked to associated B12-producing bacteria. Fluorescent B12 analogue uptake experiments in NIES 4052 and Klamath AFA support a model for the uptake of exogenous B12 in these strains. Together with the detection of cobalamin-producing commensal bacteria, this suggests that B12 in AFA biomass may be linked to cyanobacterium–bacteria interactions. Overall, this study provides a genomic and experimental framework for evaluating the taxonomy, safety, genetic tractability and nutritional potential of AFA and related Nostocales.

Hydroponic agriculture is being increasingly utilized for its high productivity. Current wastewater treatment methods lead to loss of phosphate and ni…

Abstract. Understanding how photosynthetic organisms acclimate to excess light is essential for the development of robust chassis for synthetic biology app

A seasonal time series metatranscriptome dataset suggests that neutralising hydrogen peroxide in Microcystis blooms requires a complex division of labour that is further complicated by seasonality an...

The cysteine-mediated catalytic reactions are essential for redox homeostasis in photosynthetic organisms. In the genome of cyanobacterium Anabaena PCC 7120 (Anabaena), the genes encoding thioredoxin ...

The Rhizarian amoeba Paulinella chromatophora represents a unique case of primary endosymbiosis, which has acquired photosynthetic organelles (chromat…