Cyanobacterial Strains Research Articles

Molecular Identification of Some Selected Cyanobacteria and Their Antioxidant Activities

Cyanobacteria, photosynthetic prokaryotes, are promising sources of biologically active compounds with antioxidant properties, attracting interest in their potential applications in the food, pharmaceutical, and cosmetic sectors. This present study aimed to use 16S rRNA sequences for identification of some selected strains of cyanobacteria which were previously morphologically identified. The investigation of their antioxidant activities was also performed by ABTS radical scavenging assay, ORAC-fluorescein assay and metal chelating assay in this study. Molecular identification of 8 isolates revealed 1 Calothrix sp., 2 Nostoc sp., 2 Amazonocrinis sp., 2 Aulosila sp., and 1 from the Hapalosiphonaceae family. Aulosila sp. exhibited the highest ABTS inhibition (IC50: 18.87 µg/µL), followed by a Hapalosiphonaceae cyanobacterium (19.11 µg/µL) and Calothrix sp. (21.74 µg/µL). The ORAC-fluorescein assay showed Nostoc sp. TUBT05 and a Hapalosiphonaceae cyanobacterium had the highest peroxyl radical scavenging with TE values of 0.22 and 0.21 µg/µL, respectively. Nostoc sp. TUBT01 demonstrated the highest metal chelating activity (IC50: 36.48 µg/µL). The combined analysis of selected cyanobacteria revealed insights into the relationship between their taxonomy and antioxidant profiles, highlighting their potential as natural antioxidant sources. HIGHLIGHTS 16S rRNA sequencing, BLAST, and phylogenetic analysis successfully reclassified previously morphologically identified cyanobacterial isolates. Eight cyanobacterial strains were found to have antioxidant activity, indicating their potential as a source of antioxidants. Antioxidant profiling of the selected cyanobacteria classified them into 3 major groups, revealing interesting correlations between taxonomic classification and antioxidant potential. GRAPHICAL ABSTRACT

Inhibitory Effects of Microalgal Biofilm on Vibrio parahaemolyticus

Microalgae are primary producers, the first trophic level in the food webs of aquatic ecosystems. Therefore, they have many potential applications in aquaculture. This study aimed to create autotrophic biofilms from microalgae strains belonging to the Nostocaceae, Protosiphonaceae, and Scenedesmaceae, isolated in Vietnam and to select a microalgal biofilm capable of inhibiting Vibrio parahaemolyticus. The microalgal biofilms were created by attaching the microalgal strains (cyanobacterium and green algae) to substrates (coconut fibre, sugarcane bagasse and cheesecloth). Additionally, the inhibitory effect of the microalgal biofilm on V. parahaemolyticus was evaluated based on the reduction proportion of V. parahaemolyticus cell numbers in an environment with the microalgal biofilm (co-culture method) compared to those in an environment without microalgal biofilm. The results showed that coconut fibre and cheesecloth had higher coverage density and biomass content of microalgae after 72 hours of biofilm formation than the sugarcane bagasse. We also found that microalgal biofilms formed by the combination of a cyanobacterial strain NK1111 with a green microalgal strain MBN1 or MHN122 reduced 76.2% - 99.8% of V. parahaemolyticus in 96 - 120 hours of co-culture. Meanwhile, microalgal biofilm formed by the strain NK1111 and a green microalgal strain MHB231 inhibited 91.8% of V. parahaemolyticus bacterium as early as 24 hours and inhibited 99.4% of this bacteria at 120 hours of co-culture. Therefore, the microalgal biofilms consisting of the strain NK1111 and the strain MHB231 on cheesecloth or coconut fibre substrate are highly appreciated for their potential application in shrimp farms in Vietnam.

Isolation, Identification and Pigment Analysis of Novel Cyanobacterial Strains from Thermal Springs.

Cyanobacterial pigments have attracted considerable attention in industry due to their bioactive potential and natural origin. In the present study, the growth dynamics and pigment composition, in terms of chlorophyll a, total carotenoids and phycobiliprotein content, of four cyanobacterial strains isolated from thermal springs, namely Oscillatoria subbrevis CZS 2201, Phormidium ambiguum CZS 2205, Nostoc calcicola TSZ 2203, and Synechococcus sp. CZS 2204, were investigated. The analysis revealed that the maximum quantity of chlorophyll a and total carotenoids was observed in Oscillatoria subbrevis CZS 2201 (26.49 and 3.44 µg mL-1), followed by Phormidium ambiguum CZS 2205 (18.64 and 2.32 µg mL-1), whereas a minimum amount was detected in Synechococcus sp. CZS 2204 (12.13 and 1.24 µg mL-1), respectively. In addition, Oscillatoria subbrevis CZS 2201 showed higher quantity of phycobiliproteins, especially C-phycocyanin (45.81 mg g-1), C-phycoerythrin (64.17 mg g-1) and C-allophycocyanin (27.45 mg g-1). Moreover, carotenoid derivatives of Oscillatoria subbrevis CZS 2201 were also identified, among which β-carotene was the dominant form (1.94 µg mL-1), while the accumulation of zeaxanthin and myxoxanthophyll was relatively high (0.53 and 0.41 µg mL-1, respectively) compared with echinenone and cryptoxanthin (0.34 and 0.23 µg mL-1, respectively). The study revealed that Oscillatoria subbrevis CZS 2201 was a potent producer of secondary carotenoids, including myxoxanthophyll.

Description of Pegethrix niliensis sp. nov., a Novel Cyanobacterium from the Nile River Basin, Egypt: A Polyphasic Analysis and Comparative Study of Related Genera in the Oculatellales Order.

In this paper, we examine the filamentous cyanobacterial strain NILCB16 and describe it as a new species within the genus Pegethrix. The original population was sampled from a mat growing in an irrigation canal in the Nile River, Egypt. Initially classified under Plectonema or Planktolyngbya, the strain is a potential producer of the toxins microcystin and β-N-Methylamino-L-Alanine (BMAA). Additionally, we reviewed the taxonomic relationships between the Oculatellales genera. To describe the new species, we conducted a polyphasic study, encompassing 16S rRNA gene phylogenetic analyses performed using both Maximum Likelihood and Bayesian methods, sequence identity (p-distance) analysis, 16S-23S ITS secondary structures, and morphological and habitat comparisons. The phylogenetic analysis revealed that strain NILCB16 clustered within the Pegethrix clade with strong phylogenetic support, but in a distinct position from other species in the genus. The strain shared a maximum 16S rRNA gene identity of 97.3% with P. qiandaoensis and 96.1% with the type species, P. bostrychoides. Morphologically, NILCB16 can be differentiated from other species in the genus by its lack of false branching. Our phylogenetic analyses also show that Pegethrix, Cartusia, Elainella, and Maricoleus are clustered with strong phylogenetic support. They exhibit high 16S rRNA gene identity and are morphologically indistinguishable, suggesting they could potentially be merged into a single genus in the future.

Light and temperature culture conditions impact the metabolome of the cyanobacterium of therapeutic interest Planktothricoides raciborskii PMC 877.14

Cyanobacteria are ancient photosynthetic microorganisms with a long evolutionary history that have adapted to inhabit diverse environments, such as thermal waters and muds. To do so, they are known to produce a wide range of bioactive molecules likely involved in adaptative traits such as high light and/or high temperature resistance mechanisms, which makes them particularly interesting for inclusion in thermal treatments and various therapeutic applications.In this study, the impact of higher temperature and light intensity culture conditions on the metabolome of a promising cyanobacterial strain isolated from the muds of the Balaruc-les-Bains thermal station, Planktothricoides raciborskii PMC 877.14, was investigated through liquid chromatography and mass spectrometry analyses. Statistical analyses of the biological data and molecular network construction allowed for the exploration of potential metabolite induction under different culture conditions, in order to drive the production of specific metabolites aimed at coping with cellular stress. A global shift on intracellular metabolic composition was observed over time with increased biomass production. Higher light intensity was found to stimulate both growth and production of antioxidant and/or photoprotective molecules (such as ergothioneine, mycosporine-like amino acids or carotenoids) while an increase in temperature influenced the higher production of phycobilins (such as phycoerythrin and phycocyanin).These results highlight the importance of culture/environmental conditions in driving intracellular metabolite differentiation and open up new perspectives in selecting of the optimal parameters for the growth and production of bioactive molecules for therapeutic applications in the cyanobacterium P. raciborskii PMC 877.14.

Recombinant lactate-assimilating cyanobacteria reduce high-concentration culture-associated cytotoxicity in mammalian cells.

In the fields of cultured meat, biopharmaceuticals, cell therapy, and tissue engineering, large numbers of mammalian cells are required; thus, highly-concentrated cell cultures are widely adopted. In general, such cultures can lead to cell damage caused by waste product accumulation and nutritional inadequacy. In this study, a novel co-culture system where the recombinant lactate-assimilating cyanobacterial strain, KC0110, derived from euryhaline Picosynechococcus sp. PCC 7002, and mammalian muscle cells cultured across porous membranes been developed. By using the KC0110 strain, the amount of ammonium and lactate excreted from C2C12 mouse muscle cells into the culture significantly decreased. Importantly, pyruvate and some amino acids, including pyruvate-derived amino acids, also increased significantly compared to those in monoculture of C2C12 cells. It is believed that the organic acids secreted by the KC0110 strain enhance the growth of mammalian cells, leading to a reduction in high-concentration culture-induced mammalian cell damage [lactate dehydrogenase (LDH) release] through cyanobacterial co-culture. These results show that, through co-cultivation with cyanobacteria, it is possible to culture mammalian cells, alleviating cell damage, even in highly-concentrated cultures. This study demonstrated an in vitro "symbiotic circular system" that can interchange metabolites produced by phototrophs and mammalian cells.

Biogenic synthesis and characterization of antimicrobial, antioxidant, and antihemolytic zinc oxide nanoparticles from Desertifilum sp. TN-15 cell extract

Cyanobacteria, being a prominent category of phototrophic organism, exhibit substantial potential as a valuable source of bioactive compounds and phytonutrients, including liposomes, amino derivatives, proteins, and carotenoids. In this investigation, a polyphasic approach was employed to isolate and characterize a newly discovered cyanobacterial strain from a rice field in the Garh Moor district of Jhang. Desertifilum sp. TN-15, a unique and less explored cyanobacterial strain, holds significant promise as a novel candidate for the synthesis of nanoparticles. This noticeable research gap underscores the novelty and untapped potential of Desertifilum sp. TN-15 in the field of nanomedicine. The characterization of the biogenically synthesized ZnO–NPs involved the application of diverse analytical techniques. Ultraviolet–visible spectroscopy revealed a surface plasmon resonance peak at 298 nm. Fourier transform infrared spectral analysis was utilized to confirm the involvement of biomolecules in the biogenic synthesis and stability. Scanning electron microscopy was employed to probe the surface morphology of the biogenic ZnO–NPs unveiling their size of 94.80 nm and star-shaped. Furthermore, X-ray diffraction analysis substantiated the crystalline nature of ZnO–NPs, with a crystalline size measuring 46 nm. To assess the physical stability of ZnO–NPs, zeta potential and dynamic light scattering measurements were conducted, yielding values of + 31.6 mV, and 94.80 nm, respectively, indicative of favorable stability. The antibacterial capabilities of Desertifilum sp. TN-15 are attributed to its abundance of bioactive components, including proteins, liposomes, amino derivatives, and carotenoids. Through the synthesis of zinc oxide nanoparticles (ZnO–NPs) with this strain, we have effectively used these chemicals to generate nanoparticles that exhibit noteworthy antibacterial activity against Staphylococcus aureus (MIC: 30.05 ± 0.003 µg/ml). Additionally, the ZnO–NPs displayed potent antifungal activity and antioxidant properties, as well as significant antihemolytic effects on red blood cells (IC50: 4.8 µg/ml). Cytotoxicity assessment using brine shrimps revealed an IC50 value of 3.1 µg/ml. The multifaceted actions of the biogenically synthesized ZnO–NPs underscore their potential applications in pharmacological and therapeutic fields. This study proposes a novel method for ZnO–NPs production utilizing the recently identified cyanobacterial strain Desertifilum sp. TN-15, highlighting the growing significance of biological systems in the environmentally friendly fabrication of metallic oxide nanomaterials.

Copper removal with chemically reinforced Leptolyngbya sp. GUEco 1015

Leptolyngbya sp. GUEco 1015, an autochthonous cyanobacterial strains isolated from copper rich hydrocarbon contaminated waterbodies of Assam (India), was subjected to different grades of two acids and one salt to retrieve their copper (Cu2+) removal efficacy. Pretreated Leptolyngbya biomass when considered as an alternative adsorbent showed better removal rate of toxic Cu2+in vitro. The experimental data confirmed that the strain could remove up to 96.77 %, 92.1 % and 88.14 % of Cu2+ with 0.3 mM HCl, 0.1 mM CaCl2, and 0.1 mM CH3COOH in pretreated in-vitro condition respectively from 0.1 ppm of initial Cu2+ concentration. A number of negatively charged functional groups (FG) like O-H, -NH, CO, diketones, C-O stretching and phenols are known to be involved in the adsorption events during the process. The study thus revealed that pretreated biomass of Leptolyngbya sp. GUEco 1015 with 0.3 mM HCl is obviously a feasible alternative as compared to CaCl2 and CH3COOH for Cu2+ removal.

Expanding the cyanobacterial flora of India: Multiple novel species of Nostoc and Desmonostoc from Jammu and Kashmir, India using a polyphasic approach.

This investigation reports the polyphasic characterization of six cyanobacterial strains that were isolated from Basantgarh village of district Udhampur in the union territory of Jammu and Kashmir, India. Morphological examination of the isolated strains indicated that the strains are members of the genus Nostoc or its morphotypes. Phylogenetic analyses using the 16S rRNA gene showed that five strains clustered in the Nostoc sensu stricto clade, whereas one strain clustered in the Desmonostoc clade. Further, comparative studies with their phylogenetically related taxa, based on morphology, folded secondary structures, phylogeny of the ITS rRNA region, and the percent genetic homology of 16S rRNA gene and ITS rRNA region clearly established the strains as novel taxa belonging to the genera Nostoc and Desmonostoc. Also, two strains 21A-PS and 2JNA-PS emerged as conspecific to each other, representing the same species of Nostoc. Hence, in accordance with the International code of Nomenclature for algae, fungi, and plants, this study describes Nostoc jammuense, Nostoc globosum, Nostoc breve, and Nostoc coriaceum, as novel species of the genus Nostoc, while Desmonostoc raii is described as a novel species of the genus Desmonostoc. This study adds novel species of Nostoc from Indian habitats and reinforces the need to explore the Nostoc sensu stricto clade for more novel taxa.

Study of the Effects of Bioactive Compounds of Cyanobacterium Desmonostoc alborizicum on Pathogenic Fungi of Wheat

Wheat, as one of the most economically important crops, constitutes a major part of the human diet. One of the major challenges in wheat preservation is combating various pests, including fungi, through different pesticides. Due to the toxicity caused in agricultural fields by chemical pesticides, there is a growing inclination towards using biopesticides instead. These biopesticides not only possess antimicrobial properties but also aid in the growth and development of crops. In this context, the bioactive compounds present in cyanobacteria are considered as potential biopesticide candidates. Therefore, the aim of this study is to observe the antifungal effect of bioactive compounds from the cyanobacterium Desmonostoc alborizicum on pathogenic fungi affecting wheat. For this purpose, after culturing the cyanobacterial strain Desmonostoc alborizicum for 14 days, the cyanobacterial extract was applied to wheat plants infected with the fungi Alternaria alternata, Fusarium oxysporum, Aspergillus terreus, and Phytophthora nicotiana var. The activity of antioxidant enzymes and MTT assay on 4T1 cells were then evaluated. The results showed that Aspergillus terreus exhibited the highest resistance, while Fusarium oxysporum showed the highest sensitivity to the cyanobacterial extract of Desmonostoc alborizicum. The activity of the enzymes guaiacol peroxidase, superoxide dismutase, catalase, and glutathione peroxidase in infected plants treated with the cyanobacterial extract significantly decreased (p<0.05), indicating effective stress control and enhanced immune response in these treatments. Therefore, the results of this study suggest that the use of Desmonostoc alborizicum extract can be effective as an antifungal agent in protecting wheat and other agricultural crops.

Genome-Scale Metabolic Model Reconstruction and Investigation into the Fluxome of the Fast-Growing Cyanobacterium Synechococcus sp. PCC 11901.

The ability to convert atmospheric CO2 and light into biomass and value-added chemicals makes cyanobacteria a promising resource microbial host for biotechnological applications. A newly discovered fastest-growing cyanobacterial strain, Synechococcus sp. PCC 11901, has been reported to have the highest biomass accumulation rate, making it a preferred target host for producing renewable fuels, value-added biochemicals, and natural products. System-level knowledge of an organism is imperative to understand the metabolic potential of the strain, which can be attained by developing genome-scale metabolic models (GEMs). We present the first genome-scale metabolic model of Synechococcus sp. PCC 11901 (iRS840), which contains 840 genes, 1001 reactions, and 944 metabolites. The model has been optimized and validated under different trophic modes, i.e., autotrophic and mixotrophic, by conducting an in vivo growth experiment. The robustness of the metabolic network was evaluated by changing the biomass coefficient of the model, which showed a higher sensitivity toward pigments under the photoautotrophic condition, whereas under the heterotrophic condition, amino acids were found to be more influential. Furthermore, it was discovered that PCC 11901 synthesizes succinyl-CoA via succinic semialdehyde due to its imperfect TCA cycle. Subsequent flux balance analysis (FBA) revealed a quantum yield of 0.16 in silico, which is higher compared to that of PCC 6803. Under mixotrophic conditions (with glycerol and carbon dioxide), the flux through the Calvin cycle increased compared to autotrophic conditions. This model will be useful for gaining insights into the metabolic potential of PCC 11901 and developing effective metabolic engineering strategies for product development.

Exploring the cyanobacterial diversity in Portugal: Description of four new genera from LEGE-CC using thepolyphasic approach.

Culture collections such as the Blue Biotechnology and Ecotoxicology Culture Collection (LEGE-CC) hold approximately 1200 cyanobacterial strains and are critical community resources. However, many isolates in this and other collections have not been described with a polyphasic approach, and this limits further study. Here, we employed a polyphasic methodology that integrates 16S rRNA gene phylogenetic analyses, similarity (p-distance), 16S-23S ITS rRNA region secondary structures, morphological analyses, and habitat assessments to describe four novel cyanobacterial genera from the LEGE-CC, Portugal. Pseudolimnococcus planktonicus gen. et sp. nov. (Chroococcales) is phylogenetically and morphologically related to Limnococcus. The 16S rRNA gene similarity between the types of both genera is only 93.1%. Morphologically, Pseudolimnococcus cells do not reach the original spherical shape before the next division or have aerotopes and firm mucilage, while Limnococcus cells reach the original shape, lack aerotopes, and have diffluent mucilage. Eucapsopsis lusitanus gen. et sp. nov. (Chroococcales) is morphologically similar to Eucapsis but differs from it by having aerotopes and diffluent envelope. Eucapsis lacks aerotopes and has firm mucilaginous envelopes, rarely diffluent. Both genera are phylogenetically very distant from each other and have only 90.68% 16S rRNA gene similarity. Pseudoacaryochloris arrabidensis gen. et sp. nov. (Acaryochloridales) differs from Acaryochloris by the lack of mucilaginous envelope, which is present in Acaryochloris. Both genera are phylogenetically distant and have only 94.1% 16S rRNA gene similarity. Moreover, Acaryochloris is marine (sponge symbiont), while Pseudoacaryochloris is from freshwater. Vasconcelosia minhoensis gen. et sp. nov. (Nodosilineales) is phylogenetically related to Cymatolege but has only 94.3% similarity with this genus. Morphologically both genera are distinct. Vasconcelosia has a Romeria-like structure, while Cymatolege has a Phormidium-like structure. In all cases the 16S-23S ITS rRNA region secondary structures are in agreement with the other analyses. These novel genera expand the diversity of cyanobacteria in culture collections.

Antifouling activity and ecotoxicological profile of the cyanobacterial oxadiazine nocuolin A

Pursuing effective and biocompatible natural compounds to supplant current biocidal antifouling (AF) technologies remains crucial and challenging. Among natural products hosts, cyanobacteria are recognized as producers of bioactive secondary metabolites that are underexplored in terms of anti-biofilm and AF potential. Nocuolin A, a natural oxadiazine previously isolated and known to be produced by different cyanobacterial strains, has demonstrated bioactive potential, particularly against tumor cell lines. Considering this potential and its exquisite chemical structure, here nocuolin A was investigated as a potential natural AF agent through an integrative approach including AF bioactivity testing across distinct levels of biological organization, mode of action assessment, ecotoxicity evaluation, and ecological risk predictions. Nocuolin A was found to inhibit the settlement of mussel (Mytilus galloprovincialis) plantigrades (EC50 = 3.905 μM) while showing no toxicity to this biofouling species (LC50 > 100 μM). Additionally, while exhibiting no inhibitory activity against the growth of five marine biofilm-forming bacterial strains, it significantly suppressed the growth of the marine biofilm-forming diatom Navicula sp. (EC50 = 1.561 μM), and had a lethal effect on this diatom species (>3.1 μM). The AF targets of nocuolin A on mussel plantigrades revealed no correlation with acetylcholinesterase and tyrosinase metabolic processes; however, proteins involved in oxidative stress, muscle regulation, and energy production were highlighted. The results also provide insights into the ecological risk of nocuolin A, including its ecotoxicity against Artemia salina nauplii (LC50 = 2.480 μM), Amphibalanus amphitrite nauplii (LC50 = 0.0162 μM), and Danio rerio embryos (LC50 = 0.0584 μM). When matching these results with simulated environmental values, nocuolin A was deemed a considerable threat to the ecosystems. While this research highlights the AF activity of nocuolin A, it also emphasizes the potential adverse environmental impact when applied in preventive coatings.

Screening of Lipid-Reducing Activity and Cytotoxicity of the Exometabolome from Cyanobacteria.

Cyanobacteria are rich producers of secondary metabolites, excreting some of these to the culture media. However, the exometabolome of cyanobacteria has been poorly studied, and few studies have dwelled on its characterization and bioactivity assessment. In this work, exometabolomes of 56 cyanobacterial strains were characterized by HR-ESI-LC-MS/MS. Cytotoxicity was assessed on two carcinoma cell lines, HepG2 and HCT116, while the reduction in lipids was tested in zebrafish larvae and in a steatosis model with fatty acid-overloaded human liver cells. The exometabolome analysis using GNPS revealed many complex clusters of unique compounds in several strains, with no identifications in public databases. Three strains reduced viability in HCT116 cells, namely Tolypotrichaceae BACA0428 (30.45%), Aphanizomenonaceae BACA0025 (40.84%), and Microchaetaceae BACA0110 (46.61%). Lipid reduction in zebrafish larvae was only observed by exposure to Dulcicalothrix sp. BACA0344 (60%). The feature-based molecular network shows that this bioactivity was highly correlated with two flavanones, a compound class described in the literature to have lipid reduction activity. The exometabolome characterization of cyanobacteria strains revealed a high chemodiversity, which supports it as a source for novel bioactive compounds, despite most of the time being overlooked.

Draft genome sequences of three Planktothrix rubescens strains cultivated from a eutrophic lake in Norwalk, Ohio (USA).

Draft genomes were generated for three filamentous toxin-producing cyanobacterial strains cultivated from aquatic sources in Ohio sequenced by NovaSeq S4. Here, we report the classification and genome statistics of Planktothrix rubescens PR221, PR222, and PR223.

Assessing the Efficacy of Cyanobacterial Strains as Oryza sativa Growth Biostimulants in Saline Environments.

Soil salinity, which affects plant photosynthesis mechanisms, significantly limits plant productivity. Soil microorganisms, including cyanobacteria, can synthesize various exometabolites that contribute to plant growth and development in several ways. These microorganisms can increase plant tolerance to salt stress by secreting various phytoprotectants; therefore, it is highly relevant to study soil microorganisms adapted to high salinity and investigate their potential to increase plant resistance to salt stress. This study evaluated the antioxidant activity of four cyanobacterial strains: Spirulina platensis Calu-532, Nostoc sp. J-14, Trichormus variabilis K-31, and Oscillatoria brevis SH-12. Among these, Nostoc sp. J-14 presented the highest antioxidant activity. Their growth-stimulating effects under saline conditions were also assessed under laboratory conditions. These results indicate that Nostoc sp. J-14 and T. variabilis K-31 show significant promise in mitigating the harmful effects of salinity on plant size and weight. Both strains notably enhanced the growth of Oryza sativa plants under saline conditions, suggesting their potential as biostimulants to improve crop productivity in saline environments. This research underscores the importance of understanding the mechanisms by which cyanobacteria increase plant tolerance to salt stress, paving the way for sustainable agricultural practices in saline areas.

Community Structure and Toxicity Potential of Cyanobacteria during Summer and Winter in a Temperate-Zone Lake Susceptible to Phytoplankton Blooms.

Cyanobacterial blooms are increasingly common during winters, especially when they are mild. The goal of this study was to determine the summer and winter phytoplankton community structure, cyanotoxin presence, and toxigenicity in a eutrophic lake susceptible to cyanobacterial blooms throughout the year, using classical microscopy, an analysis of toxic cyanometabolites, and an analysis of genes involved in biosynthesis of cyanotoxins. We also assessed whether cyanobacterial diversity in the studied lake has changed compared to what was reported in previous reports conducted several years ago. Moreover, the bloom-forming cyanobacterial strains were isolated from the lake and screened for cyanotoxin presence and toxigenicity. Cyanobacteria were the main component of the phytoplankton community in both sampling times, and, in particular, Oscillatoriales were predominant in both summer (Planktothrix/Limnothrix) and winter (Limnothrix) sampling. Compared to the winter community, the summer community was denser; richer in species; and contained alien and invasive Nostocales, including Sphaerospermopsis aphanizomenoides, Raphidiopsis raciborskii, and Raphidiopsis mediterranea. In both sampling times, the blooms contained toxigenic species with genetic determinants for the production of cylindrospermopsin and microcystins. Toxicological screening revealed the presence of microcystins in the lake in summer but no cyanotoxins in the winter period of sampling. However, several cyanobacterial strains isolated from the lake during winter and summer produced anabaenopeptins and microcystins. This study indicates that summer and winter blooms of cyanobacteria in the temperate zone can differ in biomass, structure, and toxicity, and that the toxic hazards associated with cyanobacterial blooms may potentially exist during winter.

Growth characteristics and molecular identification of indigenous Limnospira strains from Ethiopian soda lakes as a protein source

Malnutrition poses a significant global challenge in regions such as Ethiopia, particularly in children with limited dietary diversity. Arthrospira, a protein-rich cyanobacterium known for its rapid growth even under extreme conditions, is a promising solution for biomass production. This study addresses knowledge gaps in the morphological characterization and taxonomic classification of Arthrospira by focusing on precise species identification and strategic strain selection for optimal biomass production. Cyanobacterial strains were cultivated in a modified Spirulina Ogawa Terui medium at 35 °C under the photosynthetically active radiation of 160 μmol photons m−2 s−1 with a 12/12 h light/dark period in laboratory conditions. One hundred Arthrospira-like strains were isolated and characterized based on their morphological attributes according to accepted criteria, from Ethiopian soda lakes. Systematic evaluation of the growth rate comparison test identified four exceptionally fast-growing strains, with LC-30 exhibiting the highest dry weight (3.27 ± 0.51 g L˗1) and specific growth rate (1.63 ± 0.05 d˗1) among them. DNA analysis confirmed that all four examined strains belong to the Limnospira genus, specifically identified as Limnospira fusiformis. LC-30 and LA-08 demonstrated protein and phycocyanin levels (582.80 ± 0.07 and 557.90 ± 0.09 mg g˗1, respectively) comparable to those reported for Arthrospira platensis, and surpassing conventional protein sources, thus suggesting their potential for nutritional supplementation. The study highlights the importance of bioprospecting indigenous strains from soda lakes, revealing promising candidates for large-scale biomass production.

Investigation of the toxicity of Cr (VI) against cyanobacteria and the mechanism of tolerance of the cyanobacterial consortia: a quantum mechanical approach.

Hexavalent chromium (Cr (VI)) is a heavy metal that is distributed globally and poses a significant threat to the environment through various mechanisms. It can react with soil and water, leading to severe environmental damage. In this study, the toxicity of Cr (VI) was investigated by analyzing two major cyanobacteria species, Nostoc commune and Anabaena variabilis, commonly found in soil along with their consortia. The findings revealed that the toxicity mechanisms of Cr (VI) differed in individual monocultures, with Cr (VI) competing with various components. However, when the cyanobacteria species were combined, i.e., in consortia, they demonstrated an impressive retention of their functioning even in Cr (VI) concentration at 10ppm. The study also concluded that non-photochemical quenching played a critical role in minimizing Cr (VI) toxicity. Furthermore, the research examined the role of the S-cycle in the process. The quantum yield of electron flux revealed that the Cr (VI) was competing with Qa in A. variabilis and with Qb in N. commune, albeit the photosystem dysfunction is only visible in the latter. The mechanism seemed to be quantum tunneling alteration because of the Cr (VI) having different energized quantum wells. The consortia proved to be behaving in a better manner as compared to the control. Overall, this study reveals the mode of toxicity of Cr (VI) in these two important cyanobacterial strains as well as it also discusses the mechanism of tolerance of consortia against Cr (VI) toxicity.

Bioactivity of selenium nanoparticles biosynthesized by crude phycocyanin extract of Leptolyngbya sp. SSI24 cultivated on recycled filter cake wastes from sugar-industry

BackgroundBeet filter cake (BFC) is a food-grade solid waste produced by the sugar industry, constituting a permanent source of pollution. Cyanobacteria are considered a sustainable resource for various bioactive compounds such as phycocyanin pigment with valuable applications. This study aimed to use beet filter cake extract (BFCE) as an alternative medium for the economic cultivation of cyanobacterium Leptolyngbya sp. SSI24 PP723083, then biorefined the bioactive component such as phycocyanin pigment that could be used in the production of selenium nanoparticles.ResultsThe results of the batch experiment displayed that the highest protein content was in BG11medium (47.9%); however, the maximum carbohydrate and lipid content were in 25% BFCE (15.25 and 10.23%, respectively). In addition, 75% BFCE medium stimulated the phycocyanin content (25.29 mg/g) with an insignificant variation compared to BG11 (22.8 mg/g). Moreover, crude phycocyanin extract from Leptolyngbya sp SSI24 cultivated on BG11 and 75% BFCE successfully produced spherical-shaped selenium nanoparticles (Se-NPs) with mean sizes of 95 and 96 nm in both extracts, respectively. Moreover, XRD results demonstrated that the biosynthesized Se-NPs have a crystalline nature. In addition, the Zeta potential of the biosynthesized Se-NPs equals − 17 mV and − 15.03 mV in the control and 75% BFCE treatment, respectively, indicating their stability. The biosynthesized Se-NPs exhibited higher effectiveness against Gram-positive bacteria than Gram-negative bacteria. Moreover, the biosynthesized Se-NPs from BG11 had higher antioxidant activity with IC50 of 60 ± 0.7 compared to 75% BFCE medium. Further, Se-NPs biosynthesized from phycocyanin extracted from Leptolyngbya sp cultivated on 75% BFCE exhibited strong anticancer activity with IC50 of 17.31 ± 0.63 µg/ml against the human breast cancer cell line.ConclusionsThe BFCE-supplemented medium can be used for the cultivation of cyanobacterial strain for the phycocyanin accumulation that is used for the green synthesis of selenium nanoparticles that have biological applications.Graphical