Woronichinia naegeliana: A common nontoxigenic component of temperate freshwater cyanobacterial blooms with 30% of its genome in transposons

Occurrence of protease inhibitors in freshwater cyanobacterium Woronichinia naegeliana (Unger) Elenkin

Cyanobacteria are known for producing a wide array of secondary metabolites, including non-ribosomally synthesized oligopeptides, whose functions remain to be determined. Woronichinia naegeliana, a common component of freshwater blooms, represents an under-explored resource of bioactive oligopeptides. Among these oligopeptides are cyanopeptolin 1081 and anabaenopeptin 899, which have been shown to have adverse effects on zooplankton. The absolute amino acid configuration of these peptides appears typical relative to other cyanopeptolins and anabaenopeptins. To understand their toxic mechanisms, enzyme assays were conducted. The inhibitory activity of cyanopeptolin 1081 and anabaenopeptin 899 was tested against proteases such as chymotrypsin, trypsin, elastase, thrombin, and carboxypeptidase A, resulting in different activities against these enzymes. Cyanopeptolin 1081 inhibited both chymotrypsin and elastase, while anabaenopeptin 899 inhibited carboxypeptidase A but failed to inhibit the other tested enzymes at a concentration of 37 μM. The inhibitory concentration values determined here highlight that these compounds are among the most potent enzyme inhibitors in freshwater-derived cyanopeptides.

Taxonomic and functional metagenomic assessment of a Dolichospermum bloom in a large and deep lake south of the Alps

Untargeted genetic approaches can be used to explore the high metabolic versatility of cyanobacteria. In this context, a comprehensive metagenomic shotgun analysis was performed on a population of Dolichospermum lemmermannii collected during a surface bloom in Lake Garda in the summer of 2020. Using a phylogenomic approach, the almost complete metagenome-assembled genome obtained from the analysis allowed to clarify the taxonomic position of the species within the genus Dolichospermum and contributed to frame the taxonomy of this genus within the ADA group (Anabaena/Dolichospermum/Aphanizomenon). In addition to common functional traits represented in the central metabolism of photosynthetic cyanobacteria, the genome annotation uncovered some distinctive and adaptive traits that helped define the factors that promote and maintain bloom-forming heterocytous nitrogen-fixing Nostocales in oligotrophic lakes. In addition, genetic clusters were identified that potentially encode several secondary metabolites that were previously unknown in the populations evolving in the southern Alpine Lake district. These included geosmin, anabaenopetins, and other bioactive compounds. The results expanded the knowledge of the distinctive competitive traits that drive algal blooms and provided guidance for more targeted analyses of cyanobacterial metabolites with implications for human health and water resource use.

Temporal Dynamics of Cyanobacterial Bloom Community Composition and Toxin Production from Urban Lakes

With a long evolutionary history and a need to adapt to a changing environment, cyanobacteria in freshwater systems use specialized metabolites for communication, defense, and physiological processes. Furthermore, many cyanobacterial specialized metabolites and toxins present significant human health concerns due to their liver toxicity and their potential impact to drinking water. Gaps in knowledge exist with respect to changes in species diversity and toxin production during a cyanobacterial bloom (cyanoHAB) event; addressing these gaps will improve understanding of impacts to public and ecological health. In the current report we detail community and toxin composition dynamics during a late bloom period. Species diversity decreased at all study sites over the course of the bloom event, and toxin production reached a maximum at the midpoint of the event. We also isolated three new microcystins from a Microcystis dominated bloom (1-3), two of which contained unusual doubly homologated tyrosine residues (1 and 2). This work provokes intriguing questions with respect to the use of allelopathy by organisms in these systems and the presence of emerging toxic compounds that can impact public health.

Temporal Dynamics of Cyanobacterial Bloom Community Composition and Toxin Production from Urban Lakes

With a long evolutionary history and a need to adapt to a changing environment, cyanobacteria in freshwater systems use specialized metabolites for communication, defense, and physiological processes. However, the role that these metabolites play in differentiating species, maintaining microbial communities, and generating niche persistence and expansion is poorly understood. Furthermore, many cyanobacterial specialized metabolites and toxins present significant human health concerns due to their liver toxicity and their potential impact to drinking water. Gaps in knowledge exist with respect to changes in species diversity and toxin production during a cyanobacterial bloom (cyanoHAB) event; addressing these gaps will improve understanding of impacts to public and ecological health. In the current project, we utilized a multiomics strategy (DNA metabarcoding and metabolomics) to determine the cyanobacterial community composition, toxin profile, and the specialized metabolite pool at three freshwater lakes in Providence, RI during summer-fall cyanoHABs. Species diversity decreased at all study sites over the course of the bloom event, and toxin production reached a maximum at the midpoint of the event. Additionally, LC-MS/MS-based molecular networking identified new toxin congeners. This work provokes intriguing questions with respect to the use of allelopathy by organisms in these systems and the presence of emerging toxic compounds that can impact public health.

Screening of Phytoplankton Dynamics: Assessing Reservoir Ecosystem Health under Thermal Pollution from an Electrical Power Plant in the Pechora River Basin, European North

For the first time, we investigated species composition, phytoplankton community structure, and hydrochemical parameters in the artificial cooling reservoir of a major thermal power plant (TPP) in northeastern Europe located in the Pechora River basin (Komi Republic). Our research, conducted during June and August, revealed a total of 81 species of algae and cyanobacteria, with cyanobacteria predominating. Among these cyanobacteria and microalgae (Bacillariophyta and Chlorophyta), algae that serve as reliable indicators of water quality were identified. The assessment of water quality based on abundance and species composition of indicator phytoplankton species revealed that the waters of the Pechorskoe Reservoir belong to the III class (β-mesosaprobic or moderately polluted). This indicates that water quality is satisfactory, and the reservoir retains the ability to self-purify. The power plant's discharges heat the surface layers, increasing plankton communities' diversity, abundance, and biomass. Such stable warming in the upper layers throughout the season, uncommon for natural water bodies in the north, results in a slight increase in the trophic status of the studied reservoir, supported by hydrochemical analysis. These results provide valuable information about ecosystem functioning under temperature increasing for predicting changes in the phototrophic biota of small northern reservoirs facing the impacts of climate change.