Tiny Microbes with a Big Impact: The Role of Cyanobacteria and Their Metabolites in Shaping Our Future

Multi-class cyanobacterial toxin analysis using hydrophilic interaction liquid chromatography-mass spectrometry

Cyanobacteria produce diverse classes of toxins including microcystins, nodularins, anatoxins, cylindrospermopsins and saxitoxins, encompassing a range of chemical properties and mechanisms of toxicity. Comprehensive analysis of these toxins in cyanobacterial, environmental and biological samples generally requires multiple methods of extraction and analysis. In this work, a method was developed for the major classes of cyanotoxins, which comprised of a three-step liquid-solid extraction method using 75 % CH3CN with 0.1 % HCOOH and a hydrophilic interaction liquid chromatography (HILIC) elution gradient that provided retention of the less polar microcystins through to the highly polar saxitoxins. Detection was performed by tandem mass spectrometry in selected reaction monitoring mode with positive and negative polarity switching. Identification criteria included matching retention times and product ion ratios with available standards. In-house validation demonstrated good performance of the method including precision ranging from 1.5 (microcystin-LA) to 5.8 (gonyautoxin-2) % RSDs, and detection limits ranging from 0.01 (cylindrospermopsin) to 0.99 (gonyautoxin-3) µg/g in freeze dried material cyanobacteria. Recovery was assessed using spiked non-toxic cyanobacterial samples (Aphanizomenon sp.) and ranged from 83 (neosaxitoxin) to 107 % ([Dha7]microcystin-LR). As a demonstration of application, toxin profiles in cyanobacterial cultures, benthic and planktonic cyanobacteria field samples, and shellfish reference materials were successfully evaluated. The procedure is also amenable for extension to other polar toxin classes including domoic acid and guanitoxin. With increasing reports of cyanobacterial blooms globally, the method represents a powerful quantitative screening tool for measuring cyanotoxins across a broad range of samples.

Evaluation of biofilm assembly and microbial diversity on a freshwater, ferrous-hulled shipwreck

Abandoned shipwrecks are sitting at the bottom of oceans, lakes, and rivers around the world. Over time, microbial-comprised biofilms can help protect wrecks against chemical corrosion or contribute to their deterioration through microbiologically influenced corrosion (MIC) by organisms including iron-oxidizing bacteria (FeOB) and sulfate-reducing bacteria (SRB). Assessing the community assembly of these biofilms will give us a better understanding of the role these microbes play in MIC and the factors that influence it. Here, we determine if microbial community composition differs across a shallow freshwater ferrous-hulled shipwreck environment. Results suggest that there was a statistically significant difference among the sample types indicating the wreck environments around Accomac influenced the community composition. This is consistent with previous observations within an estuarine, shallow-water wreck environment. Bacteroidota, Chloroflexota, and Cyanobacteriota were the primary taxa responsible for differences among these wreck environments. Interestingly, port-side biofilm communities were significantly different than those on the starboard side suggesting physical factors of the environment drove niche partitioning on each side of the wreck. Similarly, FeOB enrichments and known FeOB taxa were found across the entire wreck but were primarily found in samples associated with the port side of the wreck. Amplicon sequencing identified both known FeOB and SRB taxa with a higher proportion of FeOB than SRB. Overall, these results indicate that there is niche partitioning of the microbial communities as well as with corrosion-causing taxa within a shallow freshwater wreck site which may lead to variation in how microbes may contribute to the protection or deterioration of these ferrous-hulled wrecks.

IMPORTANCE

The overall structure, abundance, and diversity of microbial communities on shipwrecks have recently been studied in marine aquatic environments. While previous studies have looked at the microbial communities associated with shallow-water ferrous-hulled wrecks in marine environments, studies focusing on freshwater wreck systems are limited. The purpose of this study was to determine microbial community diversity and composition trends across the Accomac shipwreck environment. Furthermore, shipwrecks are colonized by corrosion-causing taxa, such as iron-oxidizing bacteria and sulfate-reducing bacteria which have been shown to influence the biocorrosion of ferrous-hulled structures. Identification of various microbes in biofilms, as well as corrosion-causing microbes, can help researchers identify the role they play in aquatic ecosystem development and persistence as well as artificial reef integrity. Understanding how microbes assemble on wrecks will provide insight into preservation strategies to prevent deterioration of these wrecks over time, as well as limiting biocorrosion of similar structures.

Isolation and characterization of cyanobacteria and microalgae from a sulfuric pond: Plant growth-promoting and soil bioconsolidation activities

Sustainable alternatives are essential to improving agriculture production to meet the growing world's critical demands. Cyanobacteria and microalgae are considered renewable resources with a wide range of potential uses in the agricultural sector. We aimed to isolate cyanobacteria and microalgae from the mud of a carbon dioxide-rich sulfur pond and to investigate their plant growth-promoting (PGP) and soil bio-consolidating ability. Mud samples were subjected to DNA extraction and 16S rRNA gene sequencing to characterize the prokaryotic community. Phototrophic culturable microbiota was isolated and evaluated for different PGP properties. The most relevant isolates were combined in a consortium and used for in vitro bioconsolidation activity. In a greenhouse experiment, the isolates were evaluated for their ability to promote salinity stress tolerance in sunflower plants. Metabarcoding results showed that most Amplicon Sequence Variants (ASV) were associated with Actinobacteriota (35%), Proteobacteria (19%), and Acidobacteriota (11%) at the phylum level and Unknown (32%) and uncultured (31%) lineages at the genus level. The culture-dependent method yielded eight isolates associated with cyanobacteria and microalgae genera. The isolates obtained showed interesting PGP activities. Isolates C1, C2, and M1 were selected based on phosphate solubilization (85.6 µg PO4 3- mL-1 on average), indoles (C1 and M1 0.54 µg mL-1 IAA equivalents on average), and ACC deaminase activity (C2 and M1 6.00 µmol α-KB mg proteins-1 h-1). The consortium efficiently consolidated sand particles in the presence of calcium carbonate by forming biomineralized aggregates. In planta results showed positive effects of the consortium on Helianthus annuus L., plant growth under normal conditions and salt stress. The positive effects on soil and plants indicated their effectiveness as bioconsolidants and biostimulant agents. Our findings highlight the interesting potential of cyanobacteria and microalgae applications in sustainable agriculture.

Aerosolized Harmful Algal Bloom Toxin Microcystin-LR Induces Type 1/Type 17 Inflammation of Murine Airways

Harmful algal blooms are increasing globally and pose serious health concerns releasing cyanotoxins. Microcystin-LR (MC-LR), one of the most frequently produced cyanotoxins, has recently been detected in aerosols generated by the normal motions of affected bodies of water. MC-LR aerosol exposure has been linked to a pro-inflammatory influence on the airways of mice; however, little is understood about the underlying mechanism or the potential consequences. This study aimed to investigate the pro-inflammatory effects of aerosolized MC-LR on murine airways. C57BL/6 and BALB/c mice were exposed to MC-LR aerosols, as these strains are predisposed to type 1/type 17 and type 2 immune responses, respectively. Exposure to MC-LR induced granulocytic inflammation in C57BL/6 but not BALB/c mice, as observed by increased expression of cytokines MIP-1α, CXCL1, CCL2, and GM-CSF compared with their respective vehicle controls. Furthermore, the upregulation of interleukins IL-17A and IL-12 is consistent with Th1- and Th17-driven type 1/type 17 inflammation. Histological analysis confirmed inflammation in the C57BL/6 lungs, with elevated neutrophils and macrophages in the bronchoalveolar lavage fluid and increased pro-inflammatory and pro-resolving oxidized lipids. In contrast, BALB/c mice showed no significant airway inflammation. These results highlight the ability of aerosolized MC-LR to trigger harmful airway inflammation, requiring further research, particularly into populations with predispositions to type 1/type 17 inflammation.

A systematic comparison of natural product potential, with an emphasis on RiPPs, by mining of bacteria of three large ecosystems

The implementation of several global microbiome studies has yielded extensive insights into the biosynthetic potential of natural microbial communities. However, studies on the distribution of several classes of ribosomally synthesized and post-translationally modified peptides (RiPPs), non-ribosomal peptides (NRPs) and polyketides (PKs) in different large microbial ecosystems have been very limited. Here, we collected a large set of metagenome-assembled bacterial genomes from marine, freshwater and terrestrial ecosystems to investigate the biosynthetic potential of these bacteria. We demonstrate the utility of public dataset collections for revealing the different secondary metabolite biosynthetic potentials among these different living environments. We show that there is a higher occurrence of RiPPs in terrestrial systems, while in marine systems, we found relatively more terpene-, NRP-, and PK encoding gene clusters. Among the many new biosynthetic gene clusters (BGCs) identified, we analyzed various Nif-11-like and nitrile hydratase leader peptide (NHLP) containing gene clusters that would merit further study, including promising products, such as mersacidin-, LAP- and proteusin analogs. This research highlights the significance of public datasets in elucidating the biosynthetic potential of microbes in different living environments and underscores the wide bioengineering opportunities within the RiPP family.

Structural and functional analysis of Cyanovirin-N homologs: Carbohydrate binding affinities and antiviral potential of cyanobacterial peptides

Cyanobacteria, a group of photosynthetic prokaryotes, can sinthesize several substances due to their secondary metabolism, with notable properties, such as Cyanovirin-N(CVN), a carbohydrate-binding lectin, that exhibits antiviral activity against several pathogens, due to its ability to bind viral surface carbohydrates such as mannose, thus interfering with the viral entry on the cell. CVN has been described in several cyanobacterial strains and shows biotechnological potential for the development of drugs of pharmaceutical interest. This study focuses on the genomic exploration and characterization of Cyanovirin-N homologs to assess the conservation of carbohydrate-binding affinity within the group. The analysis of their antiviral properties was carried out using bioinformatics tools to study protein models through an in silico pipeline, following the steps of genomic prospection on public databases, homology modeling, docking, molecular dynamics and energetic analysis. Mannose served as the reference ligand, and the lectins' binding affinity with mannose was assessed across Cyanovirin-N homologs. Genomic mining identified 33 cyanobacterial lectin sequences, which underwent structural and functional characterization. The results obtained from this work indicate strong carbohydrate affinity on several homologs, pointing to the conservation of antiviral properties alongside the group. However, this affinity was not uniformly distributed among sequences, exhibiting significant heterogeneity in binding site residues, suggesting potential multi-ligand binding capabilities on the Cyanovirin-N homologs group. Studies focused on the properties involved in these molecules and the investigation of the genetic diversity of Cyanovirin-N homologs could provide valuable insights into the discovery of new drug candidates, harvesting the potential of bioinformatics for large-scale functional and structural analysis.

In vitro and in vivo assessment of antimicrobial, enzymatic, and antifouling properties of self-potent lichen symbiotic bacteria

This study aimed to comprehensively assess the antimicrobial, antifouling, and antibiofilm-forming potential of lichen symbiotic bacteria against marine fouling bacterial strains. A total of 50 lichen-associated bacteria (LAB) isolates were successfully characterized and evaluated for their effectiveness in mitigating biofouling caused by various marine biofoulers. Through a battery of biological assays encompassing enzymatic, antagonistic, antimicrobial, and antifouling assays, 15 LAB isolates were identified based on their antagonist activities. Notably, the strain LAB4 exhibited remarkable performance across all bioassays, demonstrating its proficiency as an antifouling agent. The production of crude LAB extracts was successfully scaled up using a large-scale fermentor and further optimized. Additionally, a phylogenetic analysis of the isolated strain Bacillus proteolyticus D65's 16S ribosomal RNA gene revealed a high query coverage and percentage identity of 92.62% (accession no. MK883171.1). In conclusion, the lichen bacterial symbiotic isolate B. proteolyticus exhibited significant in vitro and in vivo inhibition of foulants. This study highlights the potential of lichens as a valuable source of yet unexplored bacteria. The bacterial consortium associated with Parmotrema sp. holds promise in combatting biofouling, which poses a substantial threat to the maritime industries and their economic stability.

Biosynthesis of Dolastatin 10 in Marine Cyanobacteria, a Prototype for Multiple Approved Cancer Drugs

Dolastatin 10, a potent tubulin-targeting marine anticancer natural product, provided the basis for the development of six FDA-approved antibody-drug conjugates. Through the screening of cyanobacterial Caldora penicillata environmental DNA libraries and metagenome sequencing, we identified its biosynthetic gene cluster. Functional prediction of 10 enzymes encoded in the 39 kb cluster supports the dolastatin 10 biosynthesis. The nonheme diiron monooxygenase DolJ was biochemically characterized to mediate the terminal thiazole formation in dolastatin 10.

Sediment-driven plastisphere community assembly on plastic debris in tropical coastal and marine environments

Coastal habitats have been suggested to serve as a sink for unaccounted plastic debris, i.e., "missing plastic" in the sea, and hence, a hotspot of plastic pollution in the marine and coastal environments. Although the accumulation of plastic debris may pose significant threats to coastal ecosystems, we know little about the fate of these plastic debris and their ecological impacts due to the lack of studies on plastic-microbe interactions in coastal habitats, especially for the tropical marine and coastal environments. In this study, we collected plastic debris from 14 sites consisting of various coastal ecosystems (seagrass meadows, mangrove forests, and beaches), and marine ecosystem (coral reef) around Singapore and characterized the prokaryotic and eukaryotic microbial communities colonized on them. Our results showed that the composition of plastisphere communities in these intertidal ecosystems was predominantly influenced by the sediment than by the plastic materials. Compared with surrounding sediment and seawater, the plastic debris enriched potential plastic degraders, such as Muricauda, Halomonas, and Brevundimonas. The plastic debris was also found to host taxa that play significant roles in biogeochemical cycles (e.g., cyanobacteria, Erythrobacter), hygienically relevant bacteria (e.g., Chryseobacterium, Brevundimonas), and potential pathogens that may negatively impact the health of coastal ecosystems (e.g., Thraustochytriaceae, Labyrinthulaceae, Flavobacterium). Taken together, our study provides valuable insights into the plastic-microbe interactions in tropical coastal and marine ecosystems, highlighting the urgent need for plastisphere studies to understand the fate and ecological impacts of plastic debris accumulated in coastal habitats.

Insight to biotechnological utility of phycochemicals from cyanobacterium Anabaena sp.: An overview

Cyanobacteria (blue-green algae) are well-known for the ability to excrete extra-cellular products, as a variety of cyanochemicals (phycocompounds) of curio with several extensive therapeutic applications. Among these phycocompound, the cyanotoxins from certain water-bloom forming taxa are toxic to biota, including crocodiles. Failure of current non-renewable source compounds in producing sustainable and non-toxic therapeutics led the urgency of discovering products from natural sources. Particularly, compounds of the filamentous N2-fixing Anabaena sp. have effective antibacterial, antifungal, antioxidant, and anticancer properties. Today, such newer compounds are the potential targets for the possible novel chemical scaffolds, suitable for mainstream-drug development cascades. Bioactive compounds of Anabaena sp. such as, anatoxins, hassallidins and phycobiliproteins have proven their inherent antibacterial, antifungal, and antineoplastic activities, respectively. Herein, the available details of the biomass production and the inherent phyco-constituents namely, alkaloids, lipids, phenols, peptides, proteins, polysaccharides, terpenoids and cyanotoxins are considered, along with geographical distributions and morphological characteristics of the cyanobacterium. The acquisitions of cyanochemicals in recent years have newly addressed several pharmaceutical aliments, and the understanding of the associated molecular interactions of phycochemicals have been considered, for plausible use in drug developments in future.

Review of Marine Cyanobacteria and the Aspects Related to Their Roles: Chemical, Biological Properties, Nitrogen Fixation and Climate Change

Marine cyanobacteria are an ancient group of photosynthetic microbes dating back to 3.5 million years ago. They are prolific producers of bioactive secondary metabolites. Over millions of years, natural selection has optimized their metabolites to possess activities impacting various biological targets. This paper discusses the historical and existential records of cyanobacteria, and their role in understanding the evolution of marine cyanobacteria through the ages. Recent advancements have focused on isolating and screening bioactive compounds and their respective medicinal properties, and we also discuss chemical property space and clinical trials, where compounds with potential pharmacological effects, such as cytotoxicity, anticancer, and antiparasitic properties, are highlighted. The data have shown that about 43% of the compounds investigated have cytotoxic effects, and around 8% have anti-trypanosome activity. We discussed the role of different marine cyanobacteria groups in fixing nitrogen percentages on Earth and their outcomes in fish productivity by entering food webs and enhancing productivity in different agricultural and ecological fields. The role of marine cyanobacteria in the carbon cycle and their outcomes in improving the efficiency of photosynthetic CO2 fixation in the chloroplasts of crop plants, thus enhancing the crop plant's yield, was highlighted. Ultimately, climate changes have a significant impact on marine cyanobacteria where the temperature rises, and CO2 improves the cyanobacterial nitrogen fixation.

Antibacterial Activity against Four Fish Pathogenic Bacteria of Twelve Microalgae Species Isolated from Lagoons in Western Greece

Microalgae may produce a range of high-value bioactive substances, making them a promising resource for various applications. In this study, the antibacterial activity of twelve microalgae species isolated from lagoons in western Greece was examined against four fish pathogenic bacteria (Vibrio anguillarum, Aeromonas veronii, Vibrio alginolyticus, and Vibrio harveyi). Two experimental approaches were used to evaluate the inhibitory effect of microalgae on pathogenic bacteria. The first approach used bacteria-free microalgae cultures, whereas the second approach used filter-sterilized supernatant from centrifuged microalgae cultures. The results demonstrated that all microalgae had inhibitory effects against pathogenic bacteria in the first approach, particularly 4 days after inoculation, where Asteromonas gracilis and Tetraselmis sp. (red var., Pappas) exhibited the highest inhibitory activity, reducing bacterial growth by 1 to 3 log units. In the second approach, Tetraselmis sp. (red var., Pappas) showed significant inhibition against V. alginolyticus between 4 and 25 h after inoculation. Moreover, all tested cyanobacteria exhibited inhibitory activity against V. alginolyticus between 21 and 48 h after inoculation. Statistical analysis was performed using the independent samples t-test. These findings suggested that microalgae produce compounds with antibacterial activity, which could be useful in aquaculture.

Cyanometabolites: molecules with immense antiviral potential

Cyanometabolites are active compounds derived from cyanobacteria that include small low molecular weight peptides, oligosaccharides, lectins, phenols, fatty acids, and alkaloids. Some of these compounds may pose a threat to human and environment. However, majority of them are known to have various health benefits with antiviral properties against pathogenic viruses including Human immunodeficiency virus (HIV), Ebola virus (EBOV), Herpes simplex virus (HSV), Influenza A virus (IAV) etc. Cyanometabolites classified as lectins include scytovirin (SVN), Oscillatoria agardhii agglutinin (OAAH), cyanovirin-N (CV-N), Microcystis viridis lectin (MVL), and microvirin (MVN) also possess a potent antiviral activity against viral diseases with unique properties to recognize different viral epitopes. Studies showed that a small linear peptide, microginin FR1, isolated from a water bloom of Microcystis species, inhibits angiotensin-converting enzyme (ACE), making it useful for the treatment of coronavirus disease 2019 (COVID-19). Our review provides an overview of the antiviral properties of cyanobacteria from the late 90s till now and emphasizes the significance of their metabolites in combating viral diseases, particularly severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has received limited attention in previous publications. The enormous medicinal potential of cyanobacteria is also emphasized in this review, which justifies their use as a dietary supplement to fend off pandemics in future.

The mechanism of nanoparticle toxicity to cyanobacteria

The demand for nanoparticles is increasing tremendously, and so is the risk of their foreseeable discharge into the environment. Nanoparticles contain a variety of features, including anti-microbial properties, and have been shown to have toxic effects on aquatic organisms previously. However, the causes of nanoparticle toxicity under environmental conditions are still unknown. Exposure to nanoparticles in the environment is unavoidable as nanomaterials are used more prevalent in our daily lives, and as a result, nanotoxicity research is gaining traction. To understand the impact of nanoparticle toxicity on aquatic biota, cyanobacteria (blue-green algae) are an ideal model system. The cyanobacteria play an important role in ecological balance, nutrient cycling, energy flow, biological nitrogen fixation, and environmental remediation, and their susceptibility to nanoparticles can help in making a wise strategy for the mitigation of possible nano-pollution. This article presents an analysis of recent research findings on the toxicological influences of nanoparticles on the growth rate, biochemical changes, ultra-structural changes as well as the nanoparticle toxicity mechanisms in cyanobacteria. The finding suggests that the shading effect, generation of reactive oxygen species, membrane damage and disintegration of pigments are the main reasons for nanoparticle toxicity to the cyanobacteria.

Metagenome-Based Exploration of Bacterial Communities Associated with Cyanobacteria Strains Isolated from Thermal Muds

Cyanobacteria constitute a pioneer colonizer of specific environments for whom settlement in new biotopes precedes the establishment of composite microbial consortia. Some heterotrophic bacteria constitute cyanobacterial partners that are considered as their cyanosphere, being potentially involved in mutualistic relationships through the exchange and recycling of key nutrients and the sharing of common goods. Several non-axenic cyanobacterial strains have been recently isolated, along with their associated cyanospheres, from the thermal mud of Balaruc-les-Bains (France) and the biofilms of the retention basin where they develop. The community structure and relationships among the members of the isolated cyanobacterial strains were characterized using a metagenomic approach combined with taxonomic and microscopic descriptions of the microbial consortia. The results provided insights into the potential role and metabolic capabilities of the microorganisms of thermal mud-associated cyanobacterial biofilms. Thus, the physical proximity, host-specificity, and genetic potential functions advocate for their complementarity between cyanobacteria and their associated microbiota. Besides these findings, our results also highlighted the great influence of the reference protein database chosen for performing functional annotation of the metagenomes from organisms of the cyanosphere and the difficulty of selecting one unique database that appropriately covers both autotroph and heterotroph metabolic specificities.

Versatile Applications of Cyanobacteria in Biotechnology

Cyanobacteria are blue-green Gram-negative and photosynthetic bacteria which are seen as one of the most morphologically numerous groups of prokaryotes. Because of their ability to fix gaseous nitrogen and carbon dioxide to organic materials, they are known to play important roles in the universal nutrient cycle. Cyanobacteria has emerged as one of the promising resources to combat the issues of global warming, disease outbreaks, nutrition insecurity, energy crises as well as persistent daily human population increases. Cyanobacteria possess significant levels of macro and micronutrient substances which facilitate the versatile popularity to be utilized as human food and protein supplements in many countries such as Asia. Cyanobacteria has been employed as a complementary dietary constituent of feed for poultry and as vitamin and protein supplement in aquatic lives. They are effectively used to deal with numerous tasks in various fields of biotechnology, such as agricultural (including aquaculture), industrial (food and dairy products), environmental (pollution control), biofuel (bioenergy) and pharmaceutical biotechnology (such as antimicrobial, anti-inflammatory, immunosuppressant, anticoagulant and antitumor); recently, the growing interest of applying them as biocatalysts has been observed as well. Cyanobacteria are known to generate a numerous variety of bioactive compounds. However, the versatile potential applications of cyanobacteria in biotechnology could be their significant growth rate and survival in severe environmental conditions due to their distinct and unique metabolic pathways as well as active defensive mechanisms. In this review, we elaborated on the versatile cyanobacteria applications in different areas of biotechnology. We also emphasized the factors that could impede the implementation to cyanobacteria applications in biotechnology and the execution of strategies to enhance their effective applications.

Comparison of iCOR and Rayleigh atmospheric correction methods on Sentinel-3 OLCI images for a shallow eutrophic reservoir

Remote sensing of inland waters is challenging, but also important, due to the need to monitor the ever-increasing harmful algal blooms (HABs), which have serious effects on water quality. The Ocean and Land Color Instrument (OLCI) of the Sentinel-3 satellites program is capable of providing images for the monitoring of such waters. Atmospheric correction is a necessary process in order to retrieve the desired surface-leaving radiance signal and several atmospheric correction methods have been developed through the years. However, many of these correction methods require programming language skills, or function as commercial software plugins, limiting their possibility of use by end users. Accordingly, in this study, the free SNAP software provided by the European Space Agency (ESA) was used to evaluate the possible differences between a partial atmospheric correction method accounting for Rayleigh scattering and a full atmospheric correction method (iCOR), applied on Sentinel-3 OLCI images of a shallow, highly eutrophic water reservoir. For the complete evaluation of the two methods, in addition to the comparison of the band reflectance values, chlorophyll (CHL) and cyanobacteria (CI) indices were also calculated and their values were intercompared. The results showed, that although the absolute values between the two correction methods did not coincide, there was a very good correlation between the two methods for both bands' reflectance (r > 0.73) and the CHL and CI indices values (r > 0.95). Therefore, since iCOR correction image processing time is 25 times longer than Rayleigh correction, it is proposed that the Rayleigh partial correction method may be alternatively used for seasonal water monitoring, especially in cases of long time-series, enhancing time and resources use efficiency. Further comparisons of the two methods in other inland water bodies and evaluation with in situ chlorophyll and cyanobacteria measurements will enhance the applicability of the methodology.

Bioprospecting microalgae and cyanobacteria for biopharmaceutical applications

Microalgae and cyanobacteria have sparked a lot of interest due to their potential in various industries like biorefineries, biopharmaceuticals, food supplements, nutraceuticals, and other high-value products. Polysaccharides, vitamins, proteins, enzymes, and steroids are valuable products isolated from microalgae and cyanobacteria and potentially used in health and biomedical applications. Bioactive compounds derived from microalgae and cyanobacteria exhibit various pharmaceutical properties like antibacterial, anticancer, antiviral, antialgal, and antioxidant. From the properties listed above, the research for novel antibiotics has become particularly appropriate. In addition, the possible emergence of resistance against pathogens, as well as the potential decline in antibiotic efficacy, has prompted researchers to look for a new source of antibiotics. Microalgae and cyanobacteria have indicated a great and unexplored potential among these sources. For this reason, microalgae and cyanobacteria have been highlighted for their efficiency in different industrial sectors, as well as for their potential uses in the betterment of human and environmental health. This review gives an overview of bioactive compounds and metabolites with several biological properties isolated from microalgae and cyanobacteria for treating different animal and human diseases.

Green Synthesis and Characterization of Silver Nanoparticles with High Antibacterial Activity Using Cell Extracts of Cyanobacterium Pseudanabaena/Limnothrix sp

In this work, we demonstrated the ability of the cyanobacterium Pseudanabaena/Limnothrix sp. to produce ultra-small silver nanoparticlesin the forms of metallic silver (Ag0) and silver oxides (AgxOy) via a facile green synthetic process. The biological compounds in the cyanobacterial cellular extract acted both as reducing agents for silver ions and functional stabilizing agents for the silver nanoparticles. Furthermore, the antibacterical activity of the as-synthesized nanoparticles against Gram-negative Escherichia coli and Gram-positive Corynebacterium glutamicum bacterial cells was evaluated. The experimental results revealed a remarkable bactericidal activity of the nanoparticles that was both time-dependent and dose-dependent. In addition to their excellent bactericidal properties, the developed nanoparticles can be used as nanosupports in various environmental, biological, and medical applications.

Effects of Light and Temperature on the Metabolic Profiling of Two Habitat-Dependent Bloom-Forming Cyanobacteria

Rapid proliferation of cyanobacteria in both benthic and suspended (planktonic) habitats is a major threat to environmental safety, as they produce nuisance compounds such as cytotoxins and off-flavors, which degrade the safety and quality of water supplies. Temperature and light irradiance are two of the key factors in regulating the occurrence of algal blooms and production of major off-flavors. However, the role of these factors in regulating the growth and metabolism is poorly explored for both benthic and planktonic cyanobacteria. To fill this gap, we studied the effects of light and temperature on the growth and metabolic profiling of both benthic (Hapalosiphon sp. MRB220) and planktonic (Planktothricoides sp. SR001) environmental species collected from a freshwater reservoir in Singapore. Moreover, this study is the first report on the metabolic profiling of cyanobacteria belonging to two different habitats in response to altered environmental conditions. The highest growth rate of both species was observed at the highest light intensity (100 μmol photons/m²/s) and at a temperature of 33 °C. Systematic metabolite profiling analysis suggested that temperature had a more profound effect on metabolome of the Hapalosiphon, whereas light had a greater effect in the case of Planktothricoides. Interestingly, Planktothricoides sp. SR001 showed a specialized adaptation mechanism via biosynthesis of arginine, and metabolism of cysteine and methionine to survive and withstand higher temperatures of 38 °C and higher. Hence, the mode of strategies for coping with different light and temperature conditions was correlated with the growth and alteration in metabolic activities for physiological and ecological adaptations in both species. In addition, we putatively identified a number of unique metabolites with a broad range of antimicrobial activities in both species in response to both light and temperature. These metabolites could play a role in the dominant behavior of these species in suppressing competition during bloom formation. Overall, this study elucidated novel insights into the effects of environmental factors on the growth, metabolism, and adaptation strategies of cyanobacteria from two different habitats, and could be useful in controlling their harmful effects on human health and environmental concerns.

Cyanobacteria: Model Microorganisms and Beyond

In this review, the general background is provided on cyanobacteria, including morphology, cell membrane structure, and their photosynthesis pathway. The presence of cyanobacteria in nature, and their industrial applications are discussed, and their production of secondary metabolites are explained. Biofilm formation, as a common feature of microorganisms, is detailed and the role of cell diffusion in bacterial colonization is described. Then, the discussion is narrowed down to cyanobacterium Synechocystis, as a lab model microorganism. In this relation, the morphology of Synechocystis is discussed and its different elements are detailed. Type IV pili, the complex multi-protein apparatus for motility and cell-cell adhesion in Synechocystis is described and the underlying function of its different elements is detailed. The phototaxis behavior of the cells, in response to homogenous or directional illumination, is reported and its relation to the run and tumble statistics of the cells is emphasized. In Synechocystis suspensions, there may exist a reciprocal interaction between the cell and the carrying fluid. The effects of shear flow on the growth, doubling per day, biomass production, pigments, and lipid production of Synechocystis are reported. Reciprocally, the effects of Synechocystis presence and its motility on the rheological properties of cell suspensions are addressed. This review only takes up the general grounds of cyanobacteria and does not get into the detailed biological aspects per se. Thus, it is substantially more comprehensive in that sense than other reviews that have been published in the last two decades. It is also written not only for the researchers in the field, but for those in physics and engineering, who may find it interesting, useful, and related to their own research.

Exploring Marine as a Rich Source of Bioactive Peptides: Challenges and Opportunities from Marine Pharmacology

This review highlights the underexplored potential and promises of marine bioactive peptides (MBPs) with unique structural, physicochemical, and biological activities to fight against the current and future human pathologies. A particular focus is given to the marine environment as a significant source to obtain or extract high-value MBPs from touched/untouched sources. For instance, marine microorganisms, including microalgae, bacteria, fungi, and marine polysaccharides, are considered prolific sources of amino acids at large, and peptides/polypeptides in particular, with fundamental structural sequence and functional entities of a carboxyl group, amine, hydrogen, and a variety of R groups. Thus, MBPs with tunable features, both structural and functional entities, along with bioactive traits of clinical and therapeutic value, are of ultimate interest to reinforce biomedical settings in the 21st century. On the other front, as the largest biome globally, the marine biome is the so-called "epitome of untouched or underexploited natural resources" and a considerable source with significant potentialities. Therefore, considering their biological and biomedical importance, researchers around the globe are redirecting and/or regaining their interests in valorizing the marine biome-based MBPs. This review focuses on the widespread bioactivities of MBPs, FDA-approved MBPs in the market, sustainable development goals (SDGs), and legislation to valorize marine biome to underlying the impact role of bioactive elements with the related pathways. Finally, a detailed overview of current challenges, conclusions, and future perspectives is also given to satisfy the stimulating demands of the pharmaceutical sector of the modern world.

Cyanobacteria: A Natural Source for Controlling Agricultural Plant Diseases Caused by Fungi and Oomycetes and Improving Plant Growth

Cyanobacteria, also called blue-green algae, are a group of prokaryotic microorganisms largely distributed in both terrestrial and aquatic environments. They produce a wide range of bioactive compounds that are mostly used in cosmetics, animal feed and human food, nutraceutical and pharmaceutical industries, and the production of biofuels. Nowadays, the research concerning the use of cyanobacteria in agriculture has pointed out their potential as biofertilizers and as a source of bioactive compounds, such as phycobiliproteins, for plant pathogen control and as inducers of plant systemic resistance. The use of alternative products in place of synthetic ones for plant disease control is also encouraged by European Directive 2009/128/EC. The present up-to-date review gives an overall view of the recent results on the use of cyanobacteria for both their bioprotective effect against fungal and oomycete phytopathogens and their plant biostimulant properties. We highlight the need for considering several factors for a proper and sustainable management of agricultural crops, ranging from the mechanisms by which cyanobacteria reduce plant diseases and modulate plant resistance to the enhancement of plant growth.

3D Impedimetric Biosensor for Cyanobacteria Detection in Natural Water Sources

The excessive growth of cyanobacteria in freshwater sources produces the development of toxic blooms mainly due to the production of cyanotoxins. Here, a novel impedimetric biosensor based on a three-dimensional interdigitated electrode array (3D-IDEA) for detection of cyanobacteria cells is reported. The 3D-IDEA sensor surface biofunctionalization was performed by means of the layer-by-layer method using polyethyleneimine (PEI) as the anchoring layer and concanavalin A (Con A) as the bioreceptor to lipopolysaccharides of cyanobacteria cells. The developed PEI-Con A 3D-IDEA sensors show a linear response (R2 = 0.992) of the impedance changes (RS) versus the logarithm of cyanobacteria concentrations in the range of 102–105 cells·mL−1 with the detection limit of 100 cells·mL−1. Moreover, to prevent the interference from components that may be present in real water samples and minimize a possible sample matrix effect, a filtration methodology to recover cyanobacterial cells was developed. The proposed methodology allows 91.2% bacteria recovery, permitting to obtain results similar to controlled assays. The developed system can be used in aquatic environments to detect cyanobacteria and consequently to prevent the formation of blooms and the production of cyanotoxins. Con A can bind to most polysaccharides and so react with other types of bacteria. However, currently, on the market, it is not possible to find specific biorecognition elements for cyanobacteria. Taking into consideration the specificity of samples to be analyzed (natural water resources), it is difficult to expect high concentration of other bacteria. In this sense, the developed methodology may be used as an alarm system to select samples for more thorough and precise laboratory analysis.

Pathogens and predators impacting commercial production of microalgae and cyanobacteria

Production of phytoplankton (microalgae and cyanobacteria) in commercial raceway ponds and other systems is adversely impacted by phytoplankton pathogens, including bacteria, fungi and viruses. In addition, cultures are susceptible to productivity loss, or crash, through grazing by contaminating zooplankton such as protozoa, rotifers and copepods. Productivity loss and product contamination are also caused by otherwise innocuous invading phytoplankton that consume resources in competition with the species being cultured. This review is focused on phytoplankton competitors, pathogens and grazers of significance in commercial culture of microalgae and cyanobacteria. Detection and identification of these biological contaminants are discussed. Operational protocols for minimizing contamination, and methods of managing it, are discussed.

Species-Level Spatio-Temporal Dynamics of Cyanobacteria in a Hard-Water Temperate Lake in the Southern Baltics

Cyanobacteria are important primary producers in temperate freshwater ecosystems. However, studies on the seasonal and spatial distribution of cyanobacteria in deep lakes based on high-throughput DNA sequencing are still rare. In this study, we combined monthly water sampling and monitoring in 2019, amplicon sequence variants analysis (ASVs; a proxy for different species) and quantitative PCR targeting overall cyanobacteria abundance to describe the seasonal and spatial dynamics of cyanobacteria in the deep hard-water oligo-mesotrophic Lake Tiefer See, NE Germany. We observed significant seasonal variation in the cyanobacterial community composition (p < 0.05) in the epi- and metalimnion layers, but not in the hypolimnion. In winter-when the water column is mixed-picocyanobacteria (Synechococcus and Cyanobium) were dominant. With the onset of stratification in late spring, we observed potential niche specialization and coexistence among the cyanobacteria taxa driven mainly by light and nutrient dynamics. Specifically, ASVs assigned to picocyanobacteria and the genus Planktothrix were the main contributors to the formation of deep chlorophyll maxima along a light gradient. While Synechococcus and different Cyanobium ASVs were abundant in the epilimnion up to the base of the euphotic zone from spring to fall, Planktothrix mainly occurred in the metalimnetic layer below the euphotic zone where also overall cyanobacteria abundance was highest in summer. Our data revealed two potentially psychrotolerant (cold-adapted) Cyanobium species that appear to cope well under conditions of lower hypolimnetic water temperature and light as well as increasing sediment-released phosphate in the deeper waters in summer. The potential cold-adapted Cyanobium species were also dominant throughout the water column in fall and winter. Furthermore, Snowella and Microcystis-related ASVs were abundant in the water column during the onset of fall turnover. Altogether, these findings suggest previously unascertained and considerable spatiotemporal changes in the community of cyanobacteria on the species level especially within the genus Cyanobium in deep hard-water temperate lakes.

Unravelling unknown cyanobacteria diversity linked with HCN production

Cyanobacteria are ecologically versatile microorganisms, occupying diverse habitats, from terrestrial caves to coastal shores and from brackish lakes to thermal springs. Cyanobacteria have also been linked with hydrogen cyanide (HCN), mainly for their ability to catabolize HCN by the nitrogenase enzyme. In this context, we sampled disparate environments, spanning from Canary Islands and Iceland to Estonia and Cyprus. Eighty-one (81) strains were isolated and characterised with taxonomic indices and molecular markers (16S-23S rRNA region and cpcBA region), whilst their ability to produce HCN was evaluated. This approach resulted in the description of five new genera (Speleotes, Haliplanktos, Olisthonema, Speos, and Iphianassa) and their type species (S. anchialus, H. antonyquinny, O. eestii, S. fyssassi, I. zackieohae) representing Chroococcales, Chroococcidiopsales, Oscillatoriales, Synechococcales, and Nostocales orders, respectively. We also found unique lineages inside the genera Komarekiella, Stenomitos, Cyanocohniella, and Nodularia, describing four new species (K. chia, S. pantisii, C. hyphalmyra, N. mediterannea). We report for the first time a widespread production of HCN amongst different taxa and habitats. Epilithic lifestyle, where cyanobacteria are more vulnerable to grazers, had the largest relative frequency in HCN production. In this work, we show novel cyanobacteria diversity from various habitats, including an unexplored anchialine cave, and possible correlation of cyanobacteria chemo- with species diversity, which may have implications on strategic focusing of screening programs on underexploited taxa and/or habitats.

Bioactive Potential of Two Marine Picocyanobacteria Belonging to Cyanobium and Synechococcus Genera

Coccoid cyanobacteria produce a great variety of secondary metabolites, which may have useful properties, such as antibacterial, antiviral, anticoagulant or anticancer activities. These cyanobacterial metabolites have high ecological significance, and they could be considered responsible for the widespread occurrence of these microorganisms. Considering the great benefit derived from the identification of competent cyanobacteria for the extraction of bioactive compounds, two strains of picocyanobacteria (coccoid cyanobacteria < 3 µm) (Cyanobium sp. ITAC108 and Synechococcus sp. ITAC107) isolated from the Mediterranean sponge Petrosia ficiformis were analyzed. The biological effects of organic and aqueous extracts from these picocyanobacteria toward the nauplii of Artemia salina, sea urchin embryos and human cancer lines (HeLa cells) were evaluated. Methanolic and aqueous extracts from the two strains strongly inhibited larval development; on the contrary, in ethyl acetate and hexane extracts, the percentage of anomalous embryos was low. Moreover, all the extracts of the two strains inhibited HeLa cell proliferation, but methanol extracts exerted the highest activity. Gas chromatography–mass spectrometry analysis evidenced for the first time the presence of β-N-methylamino-l-alanine and microcystin in these picocyanobacteria. The strong cytotoxic activity observed for aqueous and methanolic extracts of these two cyanobacteria laid the foundation for the production of bioactive compounds of pharmacological interest.

Dietary nanoparticles alter the composition and function of the gut microbiota in mice at dose levels relevant for human exposure

BACKGROUND

Nanotechnologies provide new opportunities for improving the safety, quality, shelf life, flavor and appearance of foods. The most common nanoparticles (NPs) in human diet are silver metal, mainly present in food packaging and appliances, and silicon and titanium dioxides used as additives. The rapid development and commercialization of consumer products containing these engineered NPs is, however, not well supported by appropriate toxicological studies and risk assessment. Local and systemic toxicity and/or disruption of the gut microbiota (GM) have already been observed after oral administration of NPs in experimental animals, but results are not consistent and doses used were often much higher than the estimated human intakes. In view of the strong evidence linking alterations of the GM to cardiometabolic (CM) diseases, we hypothesized that dietary NPs might disturb this GM-CM axis.

MATERIALS AND METHODS

We exposed male C57BL/6JRj mice (n = 13 per dose group) to dietary NPs mixed in food pellets at doses relevant for human exposure: Ag (0, 4, 40 or 400 μg/kg pellet), SiO2 (0, 0.8, 8 and 80 mg/kg pellet) or TiO2 (0, 0.4, 4 or 40 mg/kg pellet). After 24 weeks of exposure, we assessed effects on the GM and CM health (n = 8 per dose group). The reversibility of the effects was examined after 8 additional weeks without NPs exposure (recovery period, n ≤ 5 per dose group).

RESULTS

No overt toxicity was recorded. The GM β-diversity was dose-dependently disrupted by the three NPs, and the bacterial short chain fatty acids (SCFAs) were dose-dependently reduced after the administration of SiO2 and TiO2 NPs. These effects disappeared completely or partly after the recovery period, strengthening the association with dietary NPs. We did not observe atheromatous disease or glucose intolerance after NP exposure. Instead, dose-dependent decreases in the expression of IL-6 in the liver, circulating triglycerides (TG) and urea nitrogen (BUN) were recorded after administration of the NPs.

CONCLUSION

We found that long-term oral exposure to dietary NPs at doses relevant for estimated human intakes disrupts the GM composition and function. These modifications did not appear associated with atheromatous or deleterious metabolic outcomes.

Heterologous production of cyanobacterial compounds

Cyanobacteria produce a plethora of compounds with unique chemical structures and diverse biological activities. Importantly, the increasing availability of cyanobacterial genome sequences and the rapid development of bioinformatics tools have unraveled the tremendous potential of cyanobacteria in producing new natural products. However, the discovery of these compounds based on cyanobacterial genomes has progressed slowly as the majority of their corresponding biosynthetic gene clusters (BGCs) are silent. In addition, cyanobacterial strains are often slow-growing, difficult for genetic engineering, or cannot be cultivated yet, limiting the use of host genetic engineering approaches for discovery. On the other hand, genetically tractable hosts such as Escherichia coli, Actinobacteria, and yeast have been developed for the heterologous expression of cyanobacterial BGCs. More recently, there have been increased interests in developing model cyanobacterial strains as heterologous production platforms. Herein, we present recent advances in the heterologous production of cyanobacterial compounds in both cyanobacterial and noncyanobacterial hosts. Emerging strategies for BGC assembly, host engineering, and optimization of BGC expression are included for fostering the broader applications of synthetic biology tools in the discovery of new cyanobacterial natural products.

Algal Toxic Compounds and Their Aeroterrestrial, Airborne and other Extremophilic Producers with Attention to Soil and Plant Contamination: A Review

The review summarizes the available knowledge on toxins and their producers from rather disparate algal assemblages of aeroterrestrial, airborne and other versatile extreme environments (hot springs, deserts, ice, snow, caves, etc.) and on phycotoxins as contaminants of emergent concern in soil and plants. There is a growing body of evidence that algal toxins and their producers occur in all general types of extreme habitats, and cyanobacteria/cyanoprokaryotes dominate in most of them. Altogether, 55 toxigenic algal genera (47 cyanoprokaryotes) were enlisted, and our analysis showed that besides the “standard” toxins, routinely known from different waterbodies (microcystins, nodularins, anatoxins, saxitoxins, cylindrospermopsins, BMAA, etc.), they can produce some specific toxic compounds. Whether the toxic biomolecules are related with the harsh conditions on which algae have to thrive and what is their functional role may be answered by future studies. Therefore, we outline the gaps in knowledge and provide ideas for further research, considering, from one side, the health risk from phycotoxins on the background of the global warming and eutrophication and, from the other side, the current surge of interest which phycotoxins provoke due to their potential as novel compounds in medicine, pharmacy, cosmetics, bioremediation, agriculture and all aspects of biotechnological implications in human life.

Genomic diversity and CRISPR-Cas systems in the cyanobacterium Nostoc in the High Arctic

Nostoc (Nostocales, Cyanobacteria) has a global distribution in the Polar Regions. However, the genomic diversity of Nostoc is little known and there are no genomes available for polar Nostoc. Here we carried out the first genomic analysis of the Nostoc commune morphotype with a recent sample from the High Arctic and a herbarium specimen collected during the British Arctic Expedition (1875-76). Comparisons of the polar genomes with 26 present-day non-polar members of the Nostocales family highlighted that there are pronounced genetic variations among Nostoc strains and species. Osmoprotection and other stress genes were found in all Nostoc strains, but the two Arctic strains had markedly higher numbers of biosynthetic gene clusters for uncharacterised non-ribosomal peptide synthetases, suggesting a high diversity of secondary metabolites. Since viral-host interactions contribute to microbial diversity, we analysed the CRISPR-Cas systems in the Arctic and two temperate Nostoc species. There were a large number of unique repeat-spacer arrays in each genome, indicating diverse histories of viral attack. All Nostoc strains had a subtype I-D system, but the polar specimens also showed evidence of a subtype I-B system that has not been previously reported in cyanobacteria, suggesting diverse cyanobacteria-virus interactions in the Arctic.

A short critique on biomining technology for critical materials

Being around for several decades, there is a vast amount of academic research on biomining, and yet it contributes less to the mining industry compared to other conventional technologies. This critique briefly comments on the current status of biomining research, enumerates a number of primary challenges, and elaborates on some kinetically-oriented strategies and bottom-up policies to sustain biomining with focus on critical material extraction and rare earth elements (REEs). Finally, we present some edge cutting developments which may promote new potentials in biomining.

Marine Pharmacology in 2016-2017: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The review of the 2016-2017 marine pharmacology literature was prepared in a manner similar as the 10 prior reviews of this series. Preclinical marine pharmacology research during 2016-2017 assessed 313 marine compounds with novel pharmacology reported by a growing number of investigators from 54 countries. The peer-reviewed literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities for 123 marine natural products, 111 marine compounds with antidiabetic and anti-inflammatory activities as well as affecting the immune and nervous system, while in contrast 79 marine compounds displayed miscellaneous mechanisms of action which upon further investigation may contribute to several pharmacological classes. Therefore, in 2016-2017, the preclinical marine natural product pharmacology pipeline generated both novel pharmacology as well as potentially new lead compounds for the growing clinical marine pharmaceutical pipeline, and thus sustained with its contributions the global research for novel and effective therapeutic strategies for multiple disease categories.

Anti-Inflammatory, Antioxidant, and Wound-Healing Properties of Cyanobacteria from Thermal Mud of Balaruc-Les-Bains, France: A Multi-Approach Study

Background: The Balaruc-les-Bains' thermal mud was found to be colonized predominantly by microorganisms, with cyanobacteria constituting the primary organism in the microbial biofilm observed on the mud surface. The success of cyanobacteria in colonizing this specific ecological niche can be explained in part by their taxa-specific adaptation capacities, and also the diversity of bioactive natural products that they synthesize. This array of components has physiological and ecological properties that may be exploited for various applications. Methods: Nine cyanobacterial strains were isolated from Balaruc thermal mud and maintained in the Paris Museum Collection (PMC). Full genome sequencing was performed coupled with targeted and untargeted metabolomic analyses (HPLC-DAD and LC-MS/MS). Bioassays were performed to determine antioxidant, anti-inflammatory, and wound-healing properties. Results: Biosynthetic pathways for phycobiliproteins, scytonemin, and carotenoid pigments and 124 metabolite biosynthetic gene clusters (BGCs) were characterized. Several compounds with known antioxidant or anti-inflammatory properties, such as carotenoids, phycobilins, mycosporine-like amino acids, and aeruginosins, and other bioactive metabolites like microginins, microviridins, and anabaenolysins were identified. Secretion of the proinflammatory cytokines TNF-α, IL-1β, IL-6, and IL-8 appeared to be inhibited by crude extracts of Planktothricoides raciborskii PMC 877.14, Nostoc sp. PMC 881.14, and Pseudo-chroococcus couteii PMC 885.14. The extract of the Aliinostoc sp. PMC 882.14 strain was able to slightly enhance migration of HaCat cells that may be helpful in wound healing. Several antioxidant compounds were detected, but no significant effects on nitric oxide secretion were observed. There was no cytotoxicity on the three cell types tested, indicating that cyanobacterial extracts may have anti-inflammatory therapeutic potential without harming body cells. These data open up promising uses for these extracts and their respective molecules in drugs or thermal therapies.

Beyond Microcystins: Cyanobacterial Extracts Induce Cytoskeletal Alterations in Rice Root Cells

Microcystins (MCs) are cyanobacterial toxins and potent inhibitors of protein phosphatases 1 (PP1) and 2A (PP2A), which are involved in plant cytoskeleton (microtubules and F-actin) organization. Therefore, studies on the toxicity of cyanobacterial products on plant cells have so far been focused on MCs. In this study, we investigated the effects of extracts from 16 (4 MC-producing and 12 non-MC-producing) cyanobacterial strains from several habitats, on various enzymes (PP1, trypsin, elastase), on the plant cytoskeleton and H₂O₂ levels in Oryza sativa (rice) root cells. Seedling roots were treated for various time periods (1, 12, and 24 h) with aqueous cyanobacterial extracts and underwent either immunostaining for α-tubulin or staining of F-actin with fluorescent phalloidin. 2,7-dichlorofluorescein diacetate (DCF-DA) staining was performed for H₂O₂ imaging. The enzyme assays confirmed the bioactivity of the extracts of not only MC-rich (MC+), but also MC-devoid (MC−) extracts, which induced major time-dependent alterations on both components of the plant cytoskeleton. These findings suggest that a broad spectrum of bioactive cyanobacterial compounds, apart from MCs or other known cyanotoxins (such as cylindrospermopsin), can affect plants by disrupting the cytoskeleton.

Exploitation of Filamentous and Picoplanktonic Cyanobacteria for Cosmetic Applications: Potential to Improve Skin Structure and Preserve Dermal Matrix Components

The use of natural products in skin care formulations gained interest as a concern for modern societies. The undesirable side effects of synthetic compounds, as well as the associated environmental hazards, have driven investigation on photosynthetic organisms as sustainable sources of effective and environmentally friendly ingredients. The use of natural extracts in cosmetics has been highlighted and, along with plants and algae, cyanobacteria have come into focus. Due to their low culture demands, high grow rates and ability to produce a wide variability of bioactive metabolites, cyanobacteria emerged as an economic and sustainable base for the cosmetic industry. In this study, we evaluated the potential of ethanol extracts of picocyanobacteria strains of the genera Cyanobium and Synechocystis and filamentous strains of the genera Nodosilinea, Phormidium and Tychonema for skin applications, with focus in the field of anti-aging. The extracts were analyzed for their pigment profile, phenolic content, antioxidant potential, cytotoxicity against keratinocytes (HaCat), fibroblasts (3T3L1), endothelial cells (hCMEC/D3) and capacity to inhibit hyaluronidase (HAase). The total carotenoid content ranged from 118.69 to 383.89 μg g⁻¹ of dry biomass, and the total phenolic content from 1.07 to 2.45 mg GAE g⁻¹. Identified carotenoids consisted of zeaxanthin, lutein, canthaxanthin, echinenone and β-carotene, with zeaxanthin and lutein being the most representative (49.82 and 79.08 μg g⁻¹, respectively). The highest antioxidant potential was found for Phormidium sp. LEGE 05292 and Tychonema sp. LEGE 07196 for superoxide anion radical (O₂^•−) scavenging (IC₅₀ of 822.70 and 924 μg mL⁻¹, respectively). Low or no cytotoxicity were registered. Regarding HAase inhibition, Tychonema sp. LEGE 07196 and Cyanobium sp. LEGE 07175 showed the best IC₅₀ (182.74 and 208.36 μg mL⁻¹, respectively). In addition, an increase in fibroblast proliferation was registered with these same strains. From this work, the ethanol extracts of the species Tychonema sp. and Cyanobium sp. are particularly interesting for their potential application in anti-aging formulations, once they stimulated fibroblast proliferation and inhibit hyaluronic acid digestion.

Shared PKS Module in Biosynthesis of Synergistic Laxaphycins

Cyanobacteria produce a wide range of lipopeptides that exhibit potent membrane-disrupting activities. Laxaphycins consist of two families of structurally distinct macrocyclic lipopeptides that act in a synergistic manner to produce antifungal and antiproliferative activities. Laxaphycins are produced by range of cyanobacteria but their biosynthetic origins remain unclear. Here, we identified the biosynthetic pathways responsible for the biosynthesis of the laxaphycins produced by Scytonema hofmannii PCC 7110. We show that these laxaphycins, called scytocyclamides, are produced by this cyanobacterium and are encoded in a single biosynthetic gene cluster with shared polyketide synthase enzymes initiating two distinct non-ribosomal peptide synthetase pathways. The unusual mechanism of shared enzymes synthesizing two distinct types of products may aid future research in identifying and expressing natural product biosynthetic pathways and in expanding the known biosynthetic logic of this important family of natural products.

Cyanotoxin cylindrospermopsin producers and the catalytic decomposition process: A review

Cylindrospermopsin (CYN) is a toxic secondary metabolite produced by several freshwater species of cyanobacteria. Its high chemical stability and wide biological activity pose a series of threats for human and animal morbidity and mortality. The biggest risk of CYN exposure for human organism comes from the consumption of contaminated water, fish or seafood. Very important for effective monitoring of the occurrence of CYN in aquatic environment is accurate identification of cyanobacteria species, that are potentially able to synthesize CYN. In this review we collect data about the discovery of CYN production in cyanobacteria and present the morphological changes between all its producers. Additionally we set together the results describing the catalytic decomposition of CYN.

Discovery of Unusual Cyanobacterial Tryptophan-Containing Anabaenopeptins by MS/MS-Based Molecular Networking

Heterocytous cyanobacteria are among the most prolific sources of bioactive secondary metabolites, including anabaenopeptins (APTs). A terrestrial filamentous Brasilonema sp. CT11 collected in Costa Rica bamboo forest as a black mat, was studied using a multidisciplinary approach: genome mining and HPLC-HRMS/MS coupled with bioinformatic analyses. Herein, we report the nearly complete genome consisting of 8.79 Mbp with a GC content of 42.4%. Moreover, we report on three novel tryptophan-containing APTs; anabaenopeptin 788 (1), anabaenopeptin 802 (2), and anabaenopeptin 816 (3). Furthermore, the structure of two homologues, i.e., anabaenopeptin 802 (2a) and anabaenopeptin 802 (2b), was determined by spectroscopic analysis (NMR and MS). Both compounds were shown to exert weak to moderate antiproliferative activity against HeLa cell lines. This study also provides the unique and diverse potential of biosynthetic gene clusters and an assessment of the predicted chemical space yet to be discovered from this genus.

Function analysis of RNase E in the filamentous cyanobacterium Anabaena sp. PCC 7120

RNase E is an endoribonuclease and plays a central role in RNA metabolism. Cyanobacteria, as ancient oxygen-producing photosynthetic bacteria, also contain RNase E homologues. Here, we introduced mutations into the S1 subdomain (F53A), the 5'-sensor subdomain (R160A), and the DNase I subdomain (D296A) according to the key activity sites of Escherichia coli RNase E. The results of degradation assays demonstrated that Asp296 is important to RNase E activity in Anabaena sp. PCC 7120 (hereafter PCC 7120). The docking model of RNase E in PCC 7120 (AnaRne) and RNA suggested a possible recognition mechanism of AnaRne to RNA. Moreover, overexpression of AnaRne and its N-terminal catalytic domain (AnaRneN) in vivo led to the abnormal cell division and inhibited the growth of PCC 7120. The quantitative analysis showed a significant decrease of ftsZ transcription in the case of overexpression of AnaRne or AnaRneN and ftsZ mRNA could be directly degraded by AnaRne through degradation assays in vitro, indicating that AnaRne was related to the expression of ftsZ and eventually affected cell division. In essence, our studies expand the understanding of the structural and functional evolutionary basis of RNase E and lay a foundation for further analysis of RNA metabolism in cyanobacteria.

A novel cyanobacterial geosmin producer, revising GeoA distribution and dispersion patterns in Bacteria

Cyanobacteria are ubiquitous organisms with a relevant contribution to primary production in all range of habitats. Cyanobacteria are well known for their part in worldwide occurrence of aquatic blooms while producing a myriad of natural compounds, some with toxic potential, but others of high economical impact, as geosmin. We performed an environmental survey of cyanobacterial soil colonies to identify interesting metabolic pathways and adaptation strategies used by these microorganisms and isolated, sequenced and assembled the genome of a cyanobacterium that displayed a distinctive earthy/musty smell, typical of geosmin, confirmed by GC-MS analysis of the culture's volatile extract. Morphological studies pointed to a new Oscillatoriales soil ecotype confirmed by phylogenetic analysis, which we named Microcoleus asticus sp. nov. Our studies of geosmin gene presence in Bacteria, revealed a scattered distribution among Cyanobacteria, Actinobacteria, Delta and Gammaproteobacteria, covering different niches. Careful analysis of the bacterial geosmin gene and gene tree suggests an ancient bacterial origin of the gene, that was probably successively lost in different time frames. The high sequence similarities in the cyanobacterial geosmin gene amidst freshwater and soil strains, reinforce the idea of an evolutionary history of geosmin, that is intimately connected to niche adaptation.

Newly discovered Synechococcus sp. PCC 11901 is a robust cyanobacterial strain for high biomass production

Cyanobacteria, which use solar energy to convert carbon dioxide into biomass, are potential solar biorefineries for the sustainable production of chemicals and biofuels. However, yields obtained with current strains are still uncompetitive compared to existing heterotrophic production systems. Here we report the discovery and characterization of a new cyanobacterial strain, Synechococcus sp. PCC 11901, with promising features for green biotechnology. It is naturally transformable, has a short doubling time of ≈2 hours, grows at high light intensities and in a wide range of salinities and accumulates up to ≈33 g dry cell weight per litre when cultured in a shake-flask system using a modified growth medium − 1.7 to 3 times more than other strains tested under similar conditions. As a proof of principle, PCC 11901 engineered to produce free fatty acids yielded over 6 mM (1.5 g L⁻¹), an amount comparable to that achieved by similarly engineered heterotrophic organisms.

Włodarczyk et al. discover that cyanobacterium Synechococcus sp. PCC 11901 accumulates three times more biomass than other cyanobacterial strains in the same conditions. An engineered version of this strain also produces as much free fatty acid as other commonly used heterotrophic microorganisms, suggesting its utility for the sustainable production of carbon-based molecules.

Design, Synthesis and Biological Evaluation of Jahanyne Analogs as Cell Cycle Arrest Inducers

Jahanyne, a lipopeptide with a unique terminal alkynyl and OEP (2-(1-oxo-ethyl)-pyrrolidine) moiety, exhibits anticancer activity. We synthesized jahanyne and analogs modified at the OEP moiety, employing an α-fluoromethyl ketone (FMK) strategy. Preliminary bioassays indicated that compound 1b (FMK-jahanyne) exhibited decreased activities to varying degrees against most of the cancer cells tested, whereas the introduction of a fluorine atom to the α-position of a hydroxyl group (2b) enhanced activities against all lung cancer cells. Moreover, jahanyne and 2b could induce G0/G1 cell cycle arrest in a concentration-dependent manner.

The seagrass holobiont: understanding seagrass-bacteria interactions and their role in seagrass ecosystem functioning

This review shows that the presence of seagrass microbial community is critical for the development of seagrasses; from seed germination, through to phytohormone production and enhanced nutrient availability, and defence against pathogens and saprophytes. The tight seagrass-bacterial relationship highlighted in this review supports the existence of a seagrass holobiont and adds to the growing evidence for the importance of marine eukaryotic microorganisms in sustaining vital ecosystems. Incorporating a micro-scale view on seagrass ecosystems substantially expands our understanding of ecosystem functioning and may have significant implications for future seagrass management and mitigation against human disturbance.

Cyanobacteria: Review of Current Potentials and Applications

Continual increases in the human population and growing concerns related to the energy crisis, food security, disease outbreaks, global warming, and other environmental issues require a sustainable solution from nature. One of the promising resources is cyanobacteria, also known as blue-green algae. They require simple ingredients to grow and possess a relatively simple genome. Cyanobacteria are known to produce a wide variety of bioactive compounds. In addition, cyanobacteria’s remarkable growth rate enables its potential use in a wide range of applications in the fields of bioenergy, biotechnology, natural products, medicine, agriculture, and the environment. In this review, we have summarized the potential applications of cyanobacteria in different areas of science and development, especially related to their use in producing biofuels and other valuable co-products. We have also discussed the challenges that hinder such development at an industrial level and ways to overcome such obstacles.