Application of microalgae Scenedesmus acuminatus enhances water quality in rice-crayfish culture

Improper management of aquatic environments substantially restricts the development of the aquaculture industry. The industrialisation of the crayfish Procambarus clarkii, for example, is currently being limited by poor water quality. Research suggests that microalgal biotechnology has a great potential for water quality regulation. However, the ecological effects of microalgal applications on aquatic communities in aquaculture systems remain largely unknown. In the present study, 5 L Scenedesmus acuminatus GT-2 culture (biomass 120 g L^-1) was added to an approximately 1,000 m² rice-crayfish culture to examine the response of aquatic ecosystems to microalgal application. The total nitrogen content decreased significantly as a result of microalgal addition. Moreover, the microalgal addition changed the bacterial community structure directionally and produced more nitrate reducing and aerobic bacteria. The effect of microalgal addition on plankton community structure was not obvious, except for a significant difference in Spirogyra growth which was inhibited by 81.0% under microalgal addition. Furthermore, the network of microorganisms in culture systems with the added microalga had higher interconnectivity and was more complex, which indicating microalgal application enhance the stability of aquaculture systems. The application of microalgae was found to have the greatest effect on the 6th day of the experiment, as supported by both environmental and biological evidence. These findings can provide valuable guidance for the practical application of microalgae in aquaculture systems.

Combined in vitro and in vivo investigation of barite microcrystals in Spirogyra (Zygnematophyceae, Charophyta)

We have investigated the biomineralisation of barite ‒a useful proxy for reconstructing paleoproductivity‒ in a freshwater alga, Spirogyra, by combining in vitro and in vivo approaches to unveil the nature of its barite microcrystals. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDXS) observations on simply dried samples revealed that the number and size of barite crystals were related to the barium concentration in the media. Additionally, their morphology showed a crystallographic face (011), which is not normally observed, suggesting the influence of organic molecules on the growth kinetics. The critical point drying method was used to preserve the internal and external structures of Spirogyra cells for SEM imaging. Crystals were found adjacent to the cytoplasmic membrane, near chloroplasts and fibrillary network. In vivo optical microscopy and Raman tweezer microspectroscopy in living cells showed that barite microcrystals are optically visible and follow cytoplasmic streaming. These results led us to propose that barite formation in Spirogyra occurs in the cytoplasm where barium and sulphate are both available: barium supplied non-selectively through the active transport of the divalent cations needed for actin polymerisation, and sulphate because necessary for amino acid biosynthesis in chloroplasts.

Novel biosynthesis, characterization and bio-catalytic potential of green algae (Spirogyra hyalina) mediated silver nanomaterials

In recent years green nanotechnology gained significant importance to synthesize nanoparticles due to their cost effectiveness and biosafety. In the current study, silver nanoparticles were synthesized by using extract of Spirogyra hyalina as a capping and reducing agent. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, Fourier transform infrared spectroscopy, Scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractive analysis. Silver nanoparticles give a characteristic Surface Plasmon Resonance peak of 451 nm at 2.21 a.u (arbitrary unit). SEM micrograph revealed the spherical morphology and average grain size of 52.7 nm. Furthermore, antibacterial, antifungal, insecticidal, antioxidant and membrane damage activities were determined. The maximum antibacterial and antifungal activity was observed for Pseudomonas aeruginosa (18 ± 1.2 mm) and Fusarium solani (14.3 ± 0.6 mm), respectively. In membrane damage assay, Pseudomonas aeruginosa absorbed A₂₆₀ wavelength and gave maximum peak values of 0.286, 0.434 and 0.629 at 25, 35 and 45 µg/mL of silver nanoparticles. The membrane damage assay confirmed that nanoparticles are involved in bacterial cell membrane damage. At 500 ppm silver nanoparticles showed 30% mortality against Tribolium castaneum (a common grain pest). The silver nanoparticles also showed potent antioxidant activity and successfully scavenged the DPPH free radicals upto 53.43 ± 0.17, 43.26 ± 0.97, 31.39 ± 0.33, 24.62 ± 0.85, and 14.13 ± 0.12% at a concentration of 400, 200, 100, 50, and 25 µg/mL of nanoparticles, respectively. It is concluded that silver nanoparticles can easily be synthesized by using green algae Spirogyra hyalina as a capping and reducing agent. Silver nanoparticles showed potent biomedical activities and thus can be used for therapeutic applications invitro and invivo.

Induction of Conjugation and Zygospore Cell Wall Characteristics in the Alpine Spirogyra mirabilis (Zygnematophyceae, Charophyta): Advantage under Climate Change Scenarios?

Extreme environments, such as alpine habitats at high elevation, are increasingly exposed to man-made climate change. Zygnematophyceae thriving in these regions possess a special means of sexual reproduction, termed conjugation, leading to the formation of resistant zygospores. A field sample of Spirogyra with numerous conjugating stages was isolated and characterized by molecular phylogeny. We successfully induced sexual reproduction under laboratory conditions by a transfer to artificial pond water and increasing the light intensity to 184 µmol photons m-2 s-1. This, however was only possible in early spring, suggesting that the isolated cultures had an internal rhythm. The reproductive morphology was characterized by light- and transmission electron microscopy, and the latter allowed the detection of distinctly oriented microfibrils in the exo- and endospore, and an electron-dense mesospore. Glycan microarray profiling showed that Spirogyra cell walls are rich in major pectic and hemicellulosic polysaccharides, and immuno-fluorescence allowed the detection of arabinogalactan proteins (AGPs) and xyloglucan in the zygospore cell walls. Confocal RAMAN spectroscopy detected complex aromatic compounds, similar in their spectral signature to that of Lycopodium spores. These data support the idea that sexual reproduction in Zygnematophyceae, the sister lineage to land plants, might have played an important role in the process of terrestrialization.

Filamentous green algae Spirogyra regulates methane emissions from eutrophic rivers

Excessive growth of filamentous green algae in rivers has attracted much attention due to their functional importance to primary production and carbon cycling. However, comprehensive knowledge of how filamentous green algae affect carbon cycling, especially the CH₄ emissions from river ecosystems, remains limited. In this study, incubation experiments were conducted to examine the factors regulating CH₄ emissions from a eutrophic river with dense growth of filamentous green algae Spirogyra through combinations of biogeochemical, molecular biological, and stable carbon isotope analyses. Results showed that although water dissolved oxygen (DO) in the algae+sediment (A+S) incubation groups increased up to 19 mg L^-1, average CH₄ flux of the groups was 13.09 μmol m^-2 day^-1, nearly up to two times higher than that from sediments without algae (S groups). The significant increase of sediment CH₄ oxidation potential and methanotroph abundances identified the enhancing sediment CH₄ oxidation during Spirogyra bloom. However, the increased water CH₄ concentration was consistent with depleted water [Formula: see text] and decreased apparent fractionation factor (α_app), suggesting the important contribution of Spirogyra to the oxic water CH₄ production. It can thus be concluded that high DO concentration during the algal bloom promoted the CH₄ consumption by enhancing sediment CH₄ oxidation, while algal-linked oxic water CH₄ production as a major component of water CH₄ promoted the CH₄ emissions from the river. Our study highlights the regulation of Spirogyra in aquatic CH₄ fluxes and will help to estimate accurately CH₄ emissions from eutrophic rivers with dense blooms of filamentous green algae. Graphical abstract.

in a flat-panel airlift photobioreactor

Spirogyra is a green filamentous freshwater algae on which recent studies reveal several promising properties and potential application possibilities in biotechnology. However, little is known about cultivation of Spirogyra and even less about large-scale cultivations in closed growth systems. Therefore, the aim of the present study was to elaborate the growth kinetics of Spirogyra sp. in a commercially available and scalable photobioreactor. For this purpose, Spirogyra sp. was grown indoors in distinct flat-panel airlift photobioreactors equipped with culture-flow directing installations. Hereby, special attention was laid on light administration and specific light availability and it was found that Spirogyra sp., in combination with the photobioreactor in question, required high photon-flux densities (100 µmol m-2 s-1 gDW-1) for maximum proliferation which is in accordance with its abundance in epipelagial waters in nature. Applying photon-flux densities of up to 1400 µmol m-2 s-1, a maximum volumetric productivity and final biomass concentration of 1.15 gDW L-1 day-1 and 14.28 gDW L-1 were achieved, respectively, the highest to be reported for the alga. To the knowledge of the authors, this is the first report on the growth of Spirogyra in a flat-panel photobioreactor.

Morphological and molecular profiling of Spirogyra from northeastern and northern Thailand using inter simple sequence repeat (ISSR) markers

Green algae, Spirogyra (Chlorophyta), are found in a wide range of habitats including small stagnant water bodies, rivers, and streams. Species identification of Spirogyra based on morphological characteristics has proven to be a difficult process. An accurate identification method is required to evaluate genetic variations. This study is aimed at investigating the molecular profiling of 19 samples of Spirogyra from northern and northeastern Thailand. The morphological characteristics of each sample were recorded, viz. cell dimensions (width and length), along with the number and arrangement of chloroplast spirals/pyrenoids. With regard to a correlation of the biological and ecological parameters, conductivity was clearly significantly related to the number of pyrenoids. While DO is negatively related to the number of chloroplast spirals. Molecular studies with 10 ISSR primers were amplified to examine the DNA fingerprints. Morphological characters were determined to be significantly different by revealing 5 traits (P < 0.05) for all specimens. In addition, the DNA markers of all specimens were investigated using 10 ISSR primers. The results show that the PCR technique amplified 108 fragments. An analysis of the DNA fragments grouped all samples by ISRR-PCR, which were then separated into two groups according to their distribution.

Characterization and immunomodulatory activities of polysaccharides from Spirogyra neglecta (Hassall) Kützing

Sulfated polysaccharides (SP) isolated from freshwater green algae, Spirogyra neglecta (Hassall) Kützing, and fractionated SPs were examined to investigate their molecular characteristics and immunomodulatory activity. The crude and fractionated SPs (F1, F2, and F3) consisted mostly of carbohydrates (68.5-85.3%), uronic acids (3.2-4.9%), and sulfates (2.2-12.2%) with various amounts of proteins (2.6-17.1%). D-galactose (23.5-27.3%), D-glucose (11.5-24.8%), L-fucose (19.0-26.7%), and L-rhamnose (16.4-18.3%) were the major monosaccharide units of these SPs with different levels of L-arabinose (3.0-9.4%), D-xylose (4.6-9.8%), and D-mannose (0.4-2.3%). The SPs contained two sub-fractions with molecular weights (Mw) ranging from 164 × 10(3) to 1460 × 10(3) g/mol. The crude and fractionated SPs strongly stimulated murine macrophages, producing considerable amounts of nitric oxide and various cytokines via up-regulation of their mRNA expression by activation of nuclear factor-kappa B and mitogen-activated protein kinases pathways. The main backbone of the most immunoenhancing SP was (1→3)-L-Fucopyranoside, (1→4,6)-D-Glucopyranoside, and (1→4)-D-Galactopyranoside.

Evidence for land plant cell wall biosynthetic mechanisms in charophyte green algae

BACKGROUND AND AIMS

The charophyte green algae (CGA) are thought to be the closest living relatives to the land plants, and ancestral CGA were unique in giving rise to the land plant lineage. The cell wall has been suggested to be a defining structure that enabled the green algal ancestor to colonize land. These cell walls provide support and protection, are a source of signalling molecules, and provide developmental cues for cell differentiation and elongation. The cell wall of land plants is a highly complex fibre composite, characterized by cellulose cross-linked by non-cellulosic polysaccharides, such as xyloglucan, embedded in a matrix of pectic polysaccharides. How the land plant cell wall evolved is currently unknown: early-divergent chlorophyte and prasinophyte algae genomes contain a low number of glycosyl transferases (GTs), while land plants contain hundreds. The number of GTs in CGA is currently unknown, as no genomes are available, so this study sought to give insight into the evolution of the biosynthetic machinery of CGA through an analysis of available transcriptomes.

METHODS

Available CGA transcriptomes were mined for cell wall biosynthesis GTs and compared with GTs characterized in land plants. In addition, gene cloning was employed in two cases to answer important evolutionary questions.

KEY RESULTS

Genetic evidence was obtained indicating that many of the most important core cell wall polysaccharides have their evolutionary origins in the CGA, including cellulose, mannan, xyloglucan, xylan and pectin, as well as arabino-galactan protein. Moreover, two putative cellulose synthase-like D family genes (CSLDs) from the CGA species Coleochaete orbicularis and a fragment of a putative CSLA/K-like sequence from a CGA Spirogyra species were cloned, providing the first evidence that all the cellulose synthase/-like genes present in early-divergent land plants were already present in CGA.

CONCLUSIONS

The results provide new insights into the evolution of cell walls and support the notion that the CGA were pre-adapted to life on land by virtue of the their cell wall biosynthetic capacity. These findings are highly significant for understanding plant cell wall evolution as they imply that some features of land plant cell walls evolved prior to the transition to land, rather than having evolved as a result of selection pressures inherent in this transition.

Identity and phylogenetic placement of Spirogyra species (Zygnematophyceae, Charophyta) from California streams and elsewhere(1)

Diversity of the filamentous green algae in the genus Spirogyra (Zygnematophyceae) was investigated from more than 1,200 stream samples from California. We identified 12 species of Spirogyra not previously known for California (CA), including two species new to science, Spirogyra californica sp. nov. and Spirogyra juliana sp. nov. Environmental preferences of the Californian species are discussed in the light of their restricted distribution to stream habitats with contrasting nutrient levels. We also investigated the systematic relationships of Spirogyra species from several continents using the chloroplast-encoded genes ribulose-1,5-bisphosphate carboxylase/hydrogenase large subunit (rbcL) and the beta subunit of the ATP synthase (atpB). Californian species were positioned in most major clades of Spirogyra. The phylogeny of Spirogyra and its taxonomic implications are discussed, such as the benefits of combining structural and molecular data for more accurate and consistent species identification. Considerable infraspecific genetic variation of globally distributed Spirogyra species was observed across continental scales. This finding suggests that structurally similar species from distant regions may be genetically dissimilar and that Spirogyra may contain a large number of cryptic species. Correlating the morphological and genetic variation within the genus will be a major challenge for future researchers.