Search Results (19)

Research into the effects of environmental stressors associated with global climate change (GCC) on cyanobacteria and microalgae is scarce, with bloom-forming planktonic cyanobacteria being the exception. This study aimed to address the issue by assessing morphological and biochemical changes in cyanobacterial and microalgal cells exposed to an increased temperature (T), ultraviolet radiation (UVR) and carbon dioxide (CO₂) concentration. The strains selected were Calothrix sp. SLM0211 and Coelastrella sp. SLM0503, which were isolated from a coastal environment in the central Mediterranean island of Malta. Elevated UVR had a pronounced effect on Calothrix sp. filaments, which produced screening compounds and resorted to trichome coiling to enhance self-shading. Enhanced growth was observed in cultures of Calothrix sp. grown at an increased CO₂ concentration, which produced significantly high amounts of biomass, chlorophylls and carotenoids. An increased T resulted in stunted growth and low biomass accumulation in both strains. Each strain exhibited a unique response to T and UVR stressors, which stimulated the production of exopolymeric substances (EPS) and mycosporine-like amino acids (MAAs) in cultures of Calothrix sp. and lipid production in Coelastrella sp. cells. Our findings indicate that the effects of stressors related to GCC on cyanobacterial and microalgal cells are strain-specific, making changes at community and ecosystem levels difficult to predict. Full article

Background/Objectives: Microalgae are recognized as prolific producers of bioactive metabolites with pharmaceutical potential. This study aimed to isolate and characterize cytotoxic constituents from selected cytotoxic microalgae, collected in Hue city, Vietnam. Methods: Microalgal samples were collected from freshwater bodies, morphologically identified, and maintained in laboratory culture. Thirteen strains were successfully isolated and cultivated in BG11, Z8, and BBM media to determine optimal growth conditions. Cytotoxic effects of extracts/compounds were determined using the sulforhodamine B assay on human lung cancer (SK-LU-1) and human liver cancer (HepG2) cell lines. The methanol extract was partitioned with n-hexane and CH₂Cl₂, followed by extensive chromatographic separation and HPLC purification to afford twelve compounds, including two new and ten known compounds. The structures were elucidated by HR-ESI-MS and NMR spectra, chemical methods, and comparing compounds in the literature. Results: From the phytoplankton samples collected across six freshwater bodies in Hue city, Vietnam, thirteen microalgal strains were successfully isolated and purified under laboratory conditions. These strains were morphologically and taxonomically identified to be Microcystis aeruginosa HU05, Microcystis viridis HU13, Anabaena circinalis HU08, Aphanizomenon flos-aquae HU02, Dolichospermum smithii HU04, Calothrix braunii HU14, Nostoc muscorum HU12, Nostoc punctiforme HU11, Raphidiopsis raciborskii HU03, Lyngbya spiralis HU15, Planktothrix stagnina HU16, Phormidium subtilis HU06, and Scenedesmus quadricauda HU07. All methanol extracts of those microalgae were evaluated for cytotoxic activity. The MeOH extracts of M. viridis (HU13) and D. smithii (HU04) exhibited significant cytotoxic effects, with IC₅₀ values of 6.19 ± 0.80 and 4.89 ± 0.76 µg/mL for M. viridis, and 9.51 ± 0.84 and 8.32 ± 0.94 µg/mL for D. smithii against SK-LU-1 and HepG2 cell lines, respectively. Furthermore, chemical studies of D. smithii HU04 led to the isolation of two new compounds, smithioside A (1) and smithioside B (2) and ten known ones, 3,4,5-trimethoxyphenyl-1-O-β-D-glucopyranoside (3), 4′-hydroxy-3′-methoxyphenol-β-D-[6-O-(4″-hydroxy-3″,5″-dimethoxylbenzoate)]-glucopyranoside (4), 4′-hydroxy-2′,6′-dimethoxyphenol 1-O-β-D-(6-O-syringoyl)glucopyranoside (5), mallophenol B (6), pisoninol II (7), guaiacylglycerol (8), (E)-asarone (9), deacetylsarmentamide B (10), (E)-2-hexenyl-β-D-glucopyranoside (11), and 5,6-dihydropyridin-2(1H)-one (12). The cytotoxic activity of all isolated compounds was also evaluated against SK-LU-1 and HepG2 cancer cell lines. Compound 12 showed the strongest activity, with IC₅₀ values of 9.13 ± 0.89 µM (SK-LU-1) and 7.64 ± 0.46 µM (HepG2). Compounds 5 and 6 exhibited moderate cytotoxic activity on both human cancer cell lines with IC₅₀ values ranging from 25.99 to 51.47 µM. Conclusions: These results highlight the potential of Dolichospermum smithii HU04 as a source of bioactive compounds, particularly in anticancer applications. These findings suggest that D. smithii HU04 extracts could be developed for therapeutic purposes targeting cancer. Full article

Geothermal springs are scattered worldwide and harbor thermophilic cyanobacteria, whose species distribution depends on extreme environmental conditions. The optical growth of cyanobacteria in hot springs and their metabolic diversity represent a source for possible biotechnological tools. In the current study, we isolated and characterized the cyanobacterial community of water samples from El Salado and Papallacta geothermal springs in Ecuador. We employed a culture-dependent as well as a polyphasic approach, which includes morphological examination by light microscopy, molecular analysis of 16S and 23S rRNA genes, and phylogenetic position using the maximum likelihood method. Notably, the morphological and molecular analyses complemented each other. Furthermore, we isolated eleven strains that belong to the taxa Tenebriella amphibia, Calothrix, Planktothricoides raciborskii, Nostoc, Fischerella muscicola, Leptolyngbya, Synechococcus, Komvophoron jovis, Chroococcales and Nostocacea. Both hot springs, whose temperature ranged between 45 and 54 °C, could harbor cosmopolitan and endemic cyanobacteria. Our study establishes a baseline for future efforts to exploit potential biotechnological tools bioprospected from these isolated microorganisms. Full article

The growing demand for sustainable agriculture necessitates innovative strategies to enhance crop productivity while minimizing environmental impact. This study explores the biopriming potential of Cucumis sativus L. seeds using extracts derived from a consortium of nitrofixing cyanobacteria Nostoc commune, Calothrix sp., and Aphanothece minutissima subjected to static magnetic field (SMF) treatments. The cyanobacterial consortia were exposed to SMF at varying magnetic inductions (40–50 mT and 100–200 mT), followed by extract preparation and application as biopriming agents. Results demonstrated significant improvements in key seedling growth parameters, including root and stem length, vigor index I, and fresh biomass. The consortium treated with 40–50 mT SMF showed the most pronounced growth-stimulating activity, suggesting enhanced bioactive compound production under this treatment that might be related to auxin biosynthesis. Biopriming with cyanobacterial extracts maintained a balanced nutritional uptake and plant health, as indicated by stable fresh weight dry weight ratios. These findings highlight the potential of SMF-enhanced cyanobacterial consortia as biopriming agents for horticultural crops. Future research should elucidate the underlying modes of action and optimize conditions for broader crop applications. Full article

Nitrogen-fixing cyanobacterial consortia are an alternative to the indiscriminate use of chemical fertilizers that affect the environment, fix atmospheric nitrogen, and can therefore be used as plant growth promoters, synthesize various substances such as auxins, vitamins, and total proteins, and fix atmospheric biofertilizers and soil conditioners. The present study aimed to obtain and develop, by biotechnological means, two consortia of cyanobacteria isolated from the root and rhizosphere of Carica papaya grown in sandy loam soil. The culture was carried out in Blue Green Medium without modified nitrogen (BG11₀), with aeration of 0.32 L min⁻¹, at a light intensity of 48.83 μEm⁻²s⁻¹, and a temperature of 22 ± 2 °C. Two consortia consisting of Nostoc commune, Aphanothece minutissima, Planktothrix sp. (C1), Nostoc commune, Calothrix sp., and Aphanothece minutissima (C2) were isolated and morphologically identified. The effective development of these consortia was verified at the laboratory level by obtaining biomass in dry weight as well as photosynthetic pigments, proteins, carbohydrates, and lipids. Germination parameters were determined in seeds of Cucumis sativus L. var. Market plus treated with the nitrogen-fixing cyanobacteria consortia, obtaining a higher germination percentage (>90%), greater root length (>6 cm), and higher vigour index I (513), II (13.02) for the C2 consortium. This broadens the spectrum of rhizosphere-derived microorganisms with potential as growth biostimulators. Full article

The production of isolated metallic nanoparticles with multifunctionalized properties, such as size and shape, is crucial for biomedical, photocatalytic, and energy storage or remediation applications. This study investigates the initial particle formations of gold nanoparticles (AuNPs) bioproduced in the cyanobacteria Anabaena sp. using high-resolution transmission electron microscopy images for digital image analysis. The developed method enabled the discovery of cerium nanoparticles (CeNPs), which were biosynthesized in the cyanobacteria Calothrix desertica. The particle size distributions for AuNPs and CeNPs were analyzed. After 10 h, the average equivalent circular diameter for AuNPs was 4.8 nm, while for CeNPs, it was approximately 5.2 nm after 25 h. The initial shape of AuNPs was sub-round to round, while the shape of CeNPs was more roundish due to their amorphous structure and formation restricted to heterocysts. The local PSDs indicate that the maturation of AuNPs begins in the middle of vegetative cells and near the cell membrane, compared to the other regions of the cell. Full article

Cyanobacteria play a relevant role in rice soils due to their contribution to soil fertility through nitrogen (N₂) fixation and as a promising strategy to mitigate methane (CH₄) emissions from these systems. However, information is still limited regarding the mechanisms of cyanobacterial modulation of CH₄ cycling in rice soils. Here, we focused on the response of methane cycling microbial communities to inoculation with cyanobacteria in rice soils. We performed a microcosm study comprising rice soil inoculated with either of two cyanobacterial isolates (Calothrix sp. and Nostoc sp.) obtained from a rice paddy. Our results demonstrate that cyanobacterial inoculation reduced CH₄ emissions by 20 times. Yet, the effect on CH₄ cycling microbes differed for the cyanobacterial strains. Type Ia methanotrophs were stimulated by Calothrix sp. in the surface layer, while Nostoc sp. had the opposite effect. The overall pmoA transcripts of Type Ib methanotrophs were stimulated by Nostoc. Methanogens were not affected in the surface layer, while their abundance was reduced in the sub surface layer by the presence of Nostoc sp. Our results indicate that mitigation of methane emission from rice soils based on cyanobacterial inoculants depends on the proper pairing of cyanobacteria–methanotrophs and their respective traits. Full article

Background: Advancements in DNA sequencing technology have facilitated the assessment of the connection between the oral microbiome and various diseases. The aim of the present study was to investigate the salivary microbiota composition employing for the first time in the literature the Oxford Nanopore Technology in patients affected by oral squamous cell carcinoma (OSCC). Methods: Unstimulated saliva samples of 31 patients were collected (24 OSCC patients and 7 controls). DNA was extracted using the QIAamp DNA Blood Kit and metagenomic long sequencing reads were performed using the MinION device. Results: In the OSCC group, 13 were males and 11 were females, with a mean age of 65.5 ± 13.9 years; in the control group, 5 were males and 2 were females, with a mean age of 51.4 ± 19.2 years. The border of the tongue was the most affected OSCC site. The microorganisms predominantly detected in OSCC patients were Prevotella, Chlamydia, Tissierellia, Calothrix, Leotiomycetes, Firmicutes and Zetaproteobacteria. Conclusions: This study confirmed the predominance of periodontopathic bacteria in the salivary microbiome in the OSCC group. If a direct correlation between oral dysbiosis and OSCC onset was proven, it could lead to new prevention strategies and early diagnostic tools. Full article

Windblown and water-induced erosion cause substantial soil losses worldwide, especially for drylands. Any sustainable management program that increases soil organic matter and improves the stability of the crustal layer could considerably enhance soil productivity and the preservation of erosion-prone land. This paper presents a laboratory investigation of cyanobacteria-inoculated medium sand and fine sand soils studied for severe runoff conditions that were simulated using an erosion function apparatus (EFA). Loosely deposited sand specimens prepared by air-pluviation were inoculated with a single native filamentous-cyanobacterium strain (investigating both Nostoc sp. and Calothrix sp.) and then incubated under high exposure to white light for 32- or 48-day periods. Well-developed bio-crusts were produced on the specimens’ top surface that achieved substantial improvements in erosion resistance, as was demonstrated for a wide range of hydraulic shear stress investigated using EFA experiments. Relative improvements in hydraulic erosion resistance were explained in terms of the nature of the cyanobacteria-developed microstructures (cyanobacteria filament infiltration of pore-void spaces and exopolysaccharide excretion), as were observed by scanning electron microscope examinations. The developed microstructure depended on the cyanobacterium strain employed and the nominal pore-void sizes that are related to the sand gradation and density state. The encouraging findings of this experimental investigation suggest a tailored approach (i.e., employing a suitable native cyanobacterium strain chosen for its compatibility with the soil’s physical properties) could lay the basis for developing a novel technology for soil protection. Full article

During a study of biodiversity of cyanobacteria in Gorely volcano soils (Kamchatka Peninsula), a strain of heterocytous, a false branching cyanobacterium with gradually tapered filaments, was isolated. Prominent features of the strain were purplish-grey trichomes and firm, distinct multilayered sheaths. Based on the results obtained from the morphological, ecological, and phylogenetic analysis using the 16S rRNA and 16S–23S ITS region, 16S–23S ITS secondary structure analysis, comparison of flanking regions of BoxB and V3 helices, and the p-distance between the 16S–23S ITS region, we describe our strain K7 as a novel species of the genus Roholtiella with the name Roholtiella volcanica sp. nov., in accordance with the International Code of Nomenclature for algae, fungi, and plants. This work continues the rapid expansion of the description of new taxa of cyanobacteria, and particularly demonstrates a coming phase in cyanobacterial taxonomy in which the discovery of new species in recently described genera rapidly increases our understanding of the diversity in this phylum. Full article

The biosynthesis of polyhydroxyalkanoates (PHAs) from industrial wastes by mixed microbial cultures (MMCs) enriched in PHA-accumulating bacteria is a promising technology to replace petroleum-based plastics. However, the populations’ dynamics in the PHA-accumulating MMCs are not well known. Therefore, the main objective of this study was to address the shifts in the size and structure of the bacterial communities in two lab-scale sequencing batch reactors (SBRs) fed with fish-canning effluents and operated under non-saline (SBR-N, 0.5 g NaCl/L) or saline (SBR-S, 10 g NaCl/L) conditions, by using a combination of quantitative PCR and Illumina sequencing of bacterial 16S rRNA genes. A double growth limitation (DGL) strategy, in which nitrogen availability was limited and uncoupled to carbon addition, strongly modulated the relative abundances of the PHA-accumulating bacteria, leading to an increase in the accumulation of PHAs, independently of the saline conditions (average 9.04 wt% and 11.69 wt%, maximum yields 22.03 wt% and 26.33% SBR-N and SBR-S, respectively). On the other hand, no correlations were found among the PHAs accumulation yields and the absolute abundances of total Bacteria, which decreased through time in the SBR-N and did not present statistical differences in the SBR-S. Acinetobacter, Calothrix, Dyella, Flavobacterium, Novosphingobium, Qipengyuania, and Tsukamurella were key PHA-accumulating genera in both SBRs under the DGL strategy, which was revealed as a successful tool to obtain a PHA-enriched MMC using fish-canning effluents. Full article

Periphytic algae exist widely in different waters. However, little is known about periphytic algae in long-distance water diversion channels across watersheds. We investigated the periphytic algae and the environmental factors at twenty sampling sites in the middle route of the South-to-North Water Diversion Project (MRP). The dominant species were Desmodesmus intermedius (Hegewald), Calothrix thermalis (Bornet & Flahault), Calothrix parietina (Bornet & Flahault) and Leptolyngbya benthonica (Anagnostidis) (dominance > 0.02) as measured in a whole year. Habitat heterogeneity in the MRP led to lower spatial heterogeneity and higher temporal heterogeneity of the periphytic algal community. Stochastic processes are the major process in periphytic community assembly. In deterministic processes, homogeneous selection had the major role in structuring the periphytic community, whereas the role of heterogeneous selection was less significant. In stochastic processes, dispersal limitations had the major role in structuring the periphytic community, whereas the role of homogenizing dispersal and drift were less significant. The variation in total nitrogen and total phosphorus promoted more stochastic processes (−1.96 < βNTI < 1.96). The variations in water temperature and water velocity promoted more heterogeneous selection (βNTI > 1.96). In integrating all of this empirical evidence, we explore the role of environmental factors in the action of ecological processes shaping thecommunity assembly of the periphytic algal community. Full article

The study of the importance of physicochemical parameters of water for algal growth and development in Jagdishpur Reservoir was carried out in the present research. Occurrence of algal species and values of water quality parameters also indicate the ecological nature and the present status of the reservoir. Water samples were collected from Jagdishpur Reservoir in Kapilvastu District (Nepal), in two seasons (wet and dry). The following physicochemical parameters of water were analyzed: temperature, pH, dissolved oxygen, alkalinity, concentration of nitrates and phosphates, free CO₂, hardness, conductivity, total dissolved solids. The values of free CO₂, hardness, phosphate, temperature, and dissolved oxygen were high in wet season while alkalinity, nitrate, conductivity and total dissolved solid were high in dry season. Altogether 81 algal species belonging to 53 genera and 6 classes were recorded. Higher number of algal species was recorded in the dry season rather than in the wet season. The highest number of species was noted among Chlorophyceae, followed by Cyanobacteria > Bacillariophyceae > Euglenophyceae > Crysophyceae and Dinophyceae. Cosmarium had the highest number of species (13) among all genera. During the wet season, Cosmarium, Calothrix and Phormidium were the genera with the highest number of species while Bulbochaete, Trachelomonas and Gomphonema were genera with the lowest number of species. During the dry season, Cymbella, Cosmarium and Rhopalodia were genera with highest number of species while Euglena, Gloeotrichia and Trachelomonas were genera with lowest number of species. Algal diversity was positively correlated with the increase of alkalinity, conductivity and TDS, while negatively correlated with free CO₂, hardness, concerntration of phosphates and nitrates, DO, pH and temperature. Shannon–Weiner diversity index value was higher during the dry season than in the wet season. Full article

The Sahara Desert is characterized by extreme environmental conditions, which are a unique challenge for life. Cyanobacteria are key players in the colonization of bare soils and form assemblages with other microorganisms in the top millimetres, establishing biological soil crusts (biocrusts) that cover most soil surfaces in deserts, which have important roles in the functioning of drylands. However, knowledge of biocrusts from these extreme environments is limited. Therefore, to study cyanobacterial community composition in biocrusts from the Sahara Desert, we utilized a combination of methodologies in which taxonomic assignation, for next-generation sequencing of soil samples, was based on phylogenetic analysis (16S rRNA gene) in parallel with morphological identification of cyanobacteria in natural samples and isolates from certain locations. Two close locations that differed in microenvironmental conditions were analysed. One was a dry salt lake (a “chott”), and the other was an extension of sandy, slightly saline soil. Differences in cyanobacterial composition between the sites were found, with a clear dominance of Microcoleus spp. in the less saline site, while the chott presented a high abundance of heterocystous cyanobacteria as well as the filamentous non-heterocystous Pseudophormidium sp. and the unicellular cf. Acaryochloris. The cyanobacteria found in our study area, such as Microcoleus steenstrupii, Microcoleus vaginatus, Scytonema hyalinum, Tolypothrix distorta, and Calothrix sp., are also widely distributed in other geographic locations around the world, where the conditions are less severe. Our results, therefore, indicated that some cyanobacteria can cope with polyextreme conditions, as confirmed by bioassays, and can be considered extremotolerant, being able to live in a wide range of conditions. Full article

This study aimed at examining and comparing the nutrient removal efficiency, biomass productivity and microbial community structure of two outdoor pilot-scale photobioreactors, namely a bubble column and a raceway pond, treating the liquid fraction of an agricultural digestate. Bacterial and eukaryotic communities were characterized using a metabarcoding approach and quantitative PCR. The abundance, composition, diversity, and dynamics of the main microbes were then correlated to the environmental conditions and operational parameters of the reactors. Both photobioreactors were dominated either by Chlorella sp. or Scenedesmus sp. in function of temperature, irradiance and the nitrogen compounds derived by nitrification. Other species, such as Chlamydomonas and Planktochlorella, were sporadically present, demonstrating that they have more specific niche requirement. Pseudomonas sp. always dominated the bacterial community in both reactors, except in summertime, when a bloom of Calothrix occurred in the raceway pond. In autumn, the worsening of the climate conditions decreased the microalgal growth, promoting predation by Vorticella sp. The study highlights the factors influencing the structure and dynamics of the microbial consortia and which ecological mechanisms are driving the microbial shifts and the consequent reactor performance. On these bases, control strategies could be defined to optimize the management of the microalgal-based technologies. Full article