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The optimal conditions were explored for the preparation of Spirulina blended liquor (SBL) and Spirulina fermented wine (SFW), respectively. The parameters obtaining highest alga polysaccharide were calculated by response surface methodology. The optimal conditions for SBL preparation were base liquor of 42% vol, ultrasonication time of 37‐min and ultrasonic power of 80 W with polysaccharide content (PC) and alcohol content (AC) of 0.2181 g/L and 39.7% vol, respectively. In the case of SFW, optimum fermentation occurred at 22°C, with a 4% inoculum and 6‐day period with PC and AC of 8.533 g/L and 11.2% vol, respectively. Headspace solid‐phase microextraction–gas chromatography–mass spectrometry was used to quantitatively analyze the volatile components of SBL and SFW. There were 32 and 40 main aroma compounds in SBL and SFW, respectively. Volatile organic compounds, including α‐ionone and β‐ionone, produced by Spirulina were detected in both SBL and SFW. Comparative evaluation of scavenging activity and total reducing power revealed the antioxidant capacity of SFW significantly outperformed that of SBL. [ABSTRACT FROM AUTHOR]

The adaptive evolution and coevolution of the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit ( rbc L) gene in the genus Hildenbrandia were studied based on phylogenetic tree construction and the physicochemical properties and the secondary structures of protein encoded by rbc L (Rubisco large subunit) were analyzed. The amino acids compositions and grand average of hydropathicity of freshwater H. rivularis and marine H. rubra were similar. Rubisco large subunit of Hildenbrandia was hydrophilic and the secondary structure was primarily composed of α-helixes and β-sheets, revealing the relatively stable structure of this protein. The predicted phosphorylation sites in H. rivularis and H. rubra were 33 and 36, respectively. No positive selection sites were detected in the genus Hildenbrandia , implying that rbc L gene evolved either neutrally or under purifying selection. A total of 41 coevolutionary groups were detected in the Rubisco large subunit of Hildenbrandia and the coevolving sites are in closer proximity in 3-dimensional structure of the protein. Despite the long evolutionary history, rbc L gene in genus Hildenbrandia under different environments is rather conservative.

Land‐use change has significant influences on soil respiration (Rs) in terrestrial ecosystems. Soil microbes play critical roles in soil carbon cycling. Nevertheless, the specific mechanism of how changes in soil microbial properties are linked to the variation of Rs rate during land‐use change still remains poorly understood, especially in the Loess Plateau, China. Here, the characteristics of Rs rate and soil microbial community following the land‐use change from farmland to plantation/grassland were analyzed via an automated soil CO2 flux system and high‐throughput 16S rDNA gene sequencing. The afforestation altered soil microbial diversity and community composition, which was mainly explained by soil pH, temperature, organic matter, nitrate, alkali‐hydrolyzed nitrogen, and available phosphorus. The biomarkers of Bacteroidetes, Firmicutes, and Thaumarchaeota were found in farmland soil at the phylum level. The afforestation also significantly decreased Rs rate, which was closely related to Shannon's index, Simpson's index, and some microbial taxa, such as Bacteroidetes, Firmicutes, Nitrospirae, and Acidobacteria. Bacteroidetes, and Firmicutes were particularly expected to be important drivers of high Rs rate in farmland soil. Moreover, the microbial interaction was probably also an important factor affecting Rs rate. Our results indicate that the response of Rs to land‐use change depends on soil microbial community being regulated by soil physicochemical properties in the Loess Plateau, China. [ABSTRACT FROM AUTHOR]

Salt stress is one of the abiotic stress factors that affect the normal growth and development of higher plants and algae. However, few research studies have focused on calcium stress, especially in algae. In this study, the mechanism of tolerance to high calcium stress of a Parachlorella kessleri strain was explored by the method of transcriptomics combined with physiological and morphological analysis. Concentrations of CaCl2 100 times (3.6 g/L) and 1000 times (36 g/L) greater than the standard culture were set up as stresses. The results revealed the algae could cope with high calcium stress mainly by strengthening photosynthesis, regulating osmotic pressure, and inducing antioxidant defense. Under the stress of 3.6 g/L CaCl2, the algae grew well with normal cell morphology. Although the chlorophyll content was significantly reduced, the photosynthetic efficiency was well maintained by up-regulating the expression of some photosynthesis-related genes. The cells reduced oxidative damage by inducing superoxide dismutase (SOD) activities and selenoprotein synthesis. A large number of free amino acids were produced to regulate the osmotic potential. When in higher CaCl2 stress of 36 g/L, the growth and chlorophyll content of algae were significantly inhibited. However, the algae still slowly grew and maintained the same photosynthetic efficiency, which resulted from significant up-regulation of massive photosynthesis genes. Antioxidant enzymes and glycerol were found to resist oxidative damage and osmotic stress, respectively. This study supplied algal research on CaCl2 stress and provided supporting data for further explaining the mechanism of plant salt tolerance. [ABSTRACT FROM AUTHOR]

Batrachospermaceae is the largest family of freshwater red algae, widely distributed around the world, and plays an important role in maintaining the balance of spring and creek ecosystems. The deterioration of the current global ecological environment has also destroyed the habitat of Batrachospermaceae. The research on the environmental factors of Batrachospermaceae and the accurate classification of the genus is necessary for the protection, restoration, excavation, and utilization of Batrachospermaceae resources. In this paper, the database of geographical distribution and environmental factors of Batrachospermaceae was sorted out, and the relationship between the classification of genus and environmental factors in Batrachospermaceae was analyzed based on two machine learning methods, random forest and XGBoost. The result shows: (1) The models constructed by the two machine learning methods can effectively distinguish the genus of Batrachospermaceae based on environmental factors; (2) The overall AUC score of the random forest model for the classification and prediction of the genus of Batrachospermaceae reached 90.41%, and the overall AUC score of the taxonomic prediction of each genus of Batrachospermaceae reached 85.85%; (3) Combining the two methods, it is believed that the environmental factors that affect the distinction of the genus of Batrachospermaceae are mainly altitude, average relative humidity, average temperature, and minimum temperature, among which altitude has the greatest influence. The results can further clarify the taxonomy of the genus in Batrachospermaceae and enrich the research on the differences in environmental factors of Batrachospermaceae. [ABSTRACT FROM AUTHOR]

Three species of the genus Synura from China are described here. Morphological observations and molecular phylogenetic analyses were conducted for three specimens collected at different locations in China. The described morphological features included cell size, scale size, spines, keels, and struts. Molecular analyses based on multiple genetic markers (SSU and LSU rDNA and internal transcribed spacer rDNA) were used to determine the phylogenetic positions of the three Synura species. Morphologically, specimen GZ201017 collected in Guizhou Province was characterized by a well-developed keel and lanceolate scales; specimen SX210304 collected in Shanxi Province was characterized by a less-developed keel and poor silicification; and specimen GD201126 collected in Guangdong Province was characterized mainly by spines with blunt ends or two small teeth on the tips. The morphotypes GZ201017, SX210304, and GD201126 corresponded to the original descriptions of Synura petersenii, S. glabra, and S. longitubularis, respectively. This discovery laid a foundation for the molecular phylogeny of the genus Synura and an enhanced understanding of Synura diversity and distribution in China. [ABSTRACT FROM AUTHOR]

Mercuric chloride (HgCl2) is a common heavy-metal pollutant widely used in commercial products and industry, but its excessive use and uncontrolled discharge have caused great harm to aquatic environments and human health. To research the mechanisms of HgCl2 toxicity in aquatic organisms, this study cultured the green alga Scenedesmus quadricauda in a gradient of HgCl2 concentrations (0, 0.1, 0.3, 0.5, 0.7, and 0.9 mg/L) for 9 days. The results showed that: (1) when the concentrations of HgCl2 were high (≥0.7 mg/L), the toxic effects completely inhibited the growth of algal cells, the culture liquid changed from green to light yellow, and cells aggregated and sank to the bottom. Submicroscopic structural imaging showed that at 0.9 mg/L HgCl2, the algal cells were seriously damaged and obvious plasma–wall separation occurred. Furthermore, the arrangement of photosynthetic lamellae became disordered and the nuclei and protein nuclei faded or even disappeared. (2) When the concentrations of HgCl2 were low and medium (≤0.5 mg/L), the activity of superoxide dismutase (SOD) in algal cells increased in the first five days, but the degree of increase was smaller than in the control group. However, under high HgCl2 concentrations (≥0.7 mg/L), the activity of SOD began to decrease sharply on the seventh day. The activity of peroxidase (POD) decreased more obviously than that of SOD. (3) Under medium and high HgCl2 concentrations (≥0.5 mg/L), the content of malondialdehyde (MDA) in algal cells increased over time, and had not decreased again by the last day of measurement. In contrast, the contents of total protein (TP) and soluble sugar (SS) both exhibited decreasing trends under high HgCl2 concentrations. (4) When the HgCl2 concentrations were ≥0.7 mg/L, the content of photosynthetic pigments in algal cells decreased, and the light quantum yield of PS Ⅱ decreased. At the same time, as culture time progressed, the photosynthetic electron transfer and energy-conversion efficiency were seriously damaged and photosynthesis never returned to normal levels. This research provides a reference for understanding the mechanism by which HgCl2 pollution affects aquatic ecosystems and may help with pollution management in the future. [ABSTRACT FROM AUTHOR]

Chlorophyll a concentration is an important indicator to characterize phytoplankton biomass, which further reflects the water quality of lakes. Based on the data of chlorophyll a concentration and environmental factors extracted from the ChlaData, HydroLAKES, and HELLAKES databases for Chinese lakes for three years (2000, 2005, and 2010), we used the random forest model and the generalized linear model to analyze the relationship between chlorophyll a concentration and environmental factors in Chinese lakes and predict the chlorophyll a concentration. The results showed that the relative importance of environmental factors for chlorophyll a was as follows: nutrient salt concentration > longitude and latitude > monthly mean precipitation > altitude > annual average temperature. The coefficient of determination of the random forest model was 0.9997 (R2 = 0.9997), and the root-mean-square error was 0.0010 (RMSE = 0.0010), with high prediction accuracy. The random forest model and the generalized linear model both showed that TP was the main influencing factor of chlorophyll a concentration. The validation results based on the measured data show that the models are reliable. By making more accurate predictions of chlorophyll a concentrations, we can facilitate the prevention, control, and treatment of lake blooms. [ABSTRACT FROM AUTHOR]

A new species of freshwater alga, Chara zhengzhouensis, is described and illustrated based on material collected in a lake at Zhengzhou, in Henan Province, China. Phylogenetic analysis of sequence data from the 18s rDNA, rbcL, and atpB indicated the separation between C. zhengzhouensis and other species of the genus Chara. Additionally, from a morphological point of view, C. zhengzhouensis differs from another closely related species, C. connivens, in its diplostichous cortex and corticate or ecorticate in based segments of branchlets. Therefore, the results based on both morphological observation and molecular evidence facilitated the proposal of this new species—C. zhengzhouensis. It represents another species in the charophyte diversity in China and the description of this new species provides more molecular data for phylogenetic analysis of the genus Chara. [ABSTRACT FROM AUTHOR]

In order to explore the characteristics of the periphytic algae community structure and its relationship with environmental factors in the Taiyuan region of the Fenhe River, a total of six sampling sites were investigated in July and December 2021. The effects of water quality status and environmental factors at each sampling point on the community structure of epiphytes were detected. The results showed that a total of 7 phyla and 54 genera of periphytic algae were identified in the Taiyuan region of the Fenhe River, and the species composition was mainly Bacillariophyta, Cyanophyta, and Chlorophyta. According to the analysis results of the biodiversity index, the water body of the Taiyuan region of the Fenhe River is in a state of moderate pollution. The correlation analysis between the epiphytic algae and environmental factors showed that the cell density of algae was significantly correlated with dissolved oxygen (DO), phosphate ( PO 4 3 − -P), chemical oxygen demand (COD), total phosphorus (TP), and transparency (SD) in the wet season. The algal cell density in the dry season was significantly correlated with water temperature (WT), TP, PO 4 3 − -P, and COD. According to the redundancy analysis, the community distribution of the epiphytic algae in the Taiyuan region of the Fenhe River was closely related to physical and chemical factors such as COD, nitrate nitrogen ( NO − 3   -N), WT, dissolved organic carbon (DOC), total nitrogen (TN), and TP, and COD is the main environmental factor driving the change in the community distribution of the periphytic algae in the wet season. TN is the main control factor driving the change in the biological community distribution of periphytic algae in the dry season. [ABSTRACT FROM AUTHOR]

The genus Lemanea is an evolutionally derived lineage of freshwater Rhodophyta which has a rare distribution. Morphological characterization and molecular phylogenetic analyses were conducted for a Lemanea specimen collected from Guilin, China, in this study. The results based on morphological observation and molecular evidence, including rbcL and SSU sequences, showed it was a new record of L. manipurensis Ganesan, West, Zuccarello et Rout in China. The specimen in this study was morphologically characterized by branches that were positioned in the lower part of the thallus, hair cells absent around the outer cortex, ellipsoidal and single carpospores at the top of the gonimoblast filaments and spermatangia formed in continuous wide rings on the thallus nodes. By comparing the morphology of specimens collected from Guilin, China, and the holotype specimen in India, it was found that the spermatangial shapes were variable among different populations. It was found that the presence or absence of hair cells around the outer cortex was not a reliable characteristic for the identification of the genus Lemanea based on a comparison between L. manipurensis collected in Guangxi and in India and another four Lemanea species previously recorded in China. The results of this study provided molecular evidence and a theoretical basis for molecular phylogenetic research on the genus Lemanea and enriched the species diversity and geographical distribution of Lemanea in China. [ABSTRACT FROM AUTHOR]

Eukaryotic microalgae are widespread in soil. They are generally considered to participate in soil development and the formation of the soil food chain. Interestingly, some microalgae can grow in heterotrophic mode. Therefore, it is a reasonable speculation that eukaryotic microalgae may participate in the process of soil respiration (Rs) via the heterotrophic metabolism of soil organic matter. Nevertheless, the mechanism is not well understood. Here, we investigated the eukaryotic microalgal community in farmland and plantation/grassland soil via high‐throughput sequencing focusing on the Loess Plateau, China. Chlorophyta, Chrysophyta, Cryptophyta, Bacillariophyta, Dinophyta, Xanthophyta, and Haptophyta were found in all samples. Nevertheless, the biomarker for farmland soil was affiliated to Chlorophyta and Xanthophyta, whereas the biomarker for plantation/grassland soil was affiliated to Chrysophyta. Moreover, the distribution of soil microalgae was strongly dependent on soil pH, organic matter, and nitrogen. In addition, afforestation significantly decreased Rs rate, which was significantly related to the soil microalgal community, especially 11 taxa of eukaryotic microalgae affiliating to Chlorophyta and Chrysophyta. Meanwhile, the interaction between microalgae and bacteria in farmland soil was stronger than that in plantation/grassland soil, which was also likely to affect Rs rate. These results suggest that beyond plants, soil eukaryotic microalgae are functionally significant but rarely considered participants of Rs. Therefore, they should be considered when investigating soil carbon cycling. [ABSTRACT FROM AUTHOR]

Members of coccoid green algae have been documented in various extreme environments. In this article, a unicellular green alga was found to slowly grow in high concentration (3.6 g/L) and pure calcium chloride solution in the laboratory. It was successfully cultured and a taxonomic study combined approaches of morphological and molecular methods was conducted to determine its classification attribution, which was followed by a preliminary physiology research to explore its unique tolerance characteristics against calcium chloride stress. The strain was identified as Parachlorella kessleri by very similar morphology and the same phylogenetic position. The morphological differences among the three species in genus Parachlorella were then discussed and the characteristic traits of absent or thin mucilaginous envelop and mantel‐shaped chloroplast for P. kessleri were supported. In addition, the almost strictly spherical shape of adult cells could further distinguish the P. kessleri from the other two species. The tolerant characteristics to CaCl2 stress for this strain were confirmed and the limit concentration was revealed as between 2000 and 4000 times than the standard BG11 culture concentration. Therefore, this P. kessleri strain is expected to be a good material to explore the mechanism of resistance to calcium ions stress for eukaryotic microbiology. [ABSTRACT FROM AUTHOR]

Active films from chitosan incorporated with Arthrospira platensis polysaccharide (APP) of various ratios (0.0%, 0.5%, and 1.0%, w/v) were developed by solution casting. The effect of APP on the structural, physicochemical, mechanical, antimicrobial, and antioxidant properties of the chitosan‐APP films (CA‐film) was investigated. Fourier transform infrared spectra (FTIR) confirmed successful incorporation of chitosan and APP. The compact structure of the films was observed clearly in scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. X‐ray diffraction (XRD) patterns suggest the semi‐crystalline structure was increased upon addition of APP. The composite films showed an improved water resistance and vapor barrier properties, and reduced by at least 27.4% and 32.1% in swelling degree (Sd) and water vapor permeability (WVP) compared with chitosan film (C‐film), respectively. However, the transparency decreased slightly, which may be due to the shrinkage of the spacing of the polymer interchain. The composite films also displayed enhanced the mechanical properties. The antimicrobial activity of the CA‐film showed an increase of at least of 0.41‐fold in inhibition zone diameter for E. coli. At a concentration of 1.2 mg/mL, the antioxidant activity of CA‐film was enhanced by more than threefold compared with C‐film. Therefore, CA‐films have good potential as sources of active packaging material for the food industry. [ABSTRACT FROM AUTHOR]

To research the adaptive evolution and coevolution of the rbcL gene in the genus Galdieria, 36 sequences were selected. The bioinformatics of proteins encoded by rbcL genes of Galdieria were analyzed, and phylogenetic trees were constructed by the maximum‐likelihood method. Then, adaptive evolution and coevolution were analyzed. The phylogenetic tree showed that the inner groups were clustered into four branches, in which the sequences of Galdieria maxima were divided into two small branches, and the posterior probability of each branch is above 94.9%. Eleven reliable positive selection sites were detected in the branched‐site model, indicating that the rbcL protein‐coding gene of Galdieria underwent adaptive evolution to adapt to extreme environments. Site 269 F is located in the loop 6 domain, while sites 272 D and 273 W are located in the 6‐helix structure. Many coevolution pairs were detected, which were closely related to the hydrophobic and molecular weight correlation values of amino acids. The results are helpful to research the evolution process of freshwater red algae, to explore the changes of its essential genes and protein functions to adapt to different environmental pressures, and to understand the close relationship between amino acids in proteins and the molecular mechanism of evolution. [ABSTRACT FROM AUTHOR]