Qiufeng Yan

The species of the genus Pleurastrum are rarely mentioned, and related research and reports are limited. At present, this genus only contains 8 species, however, there is no record of this genus species in China, and there is a lack of research on its diversity. In this study, we collected two isolates of algae, FACHB-3462 and FACHB-3463, from lakes and freshwater rivers on the Qinghai Tibet Plateau. Based on morphological data and phylogenetic analysis, we described P. gracilis in detail and compared its similarity with the morphology of existing species. The phylogenetic tree constructed based on the 18S rDNA sequence indicates that P. gracilis is most closely related to P. amblystomatis , P. aquaticum , and P. ellipsoideum , forming a branch independent of the genera Protosiphon , Spongiochloris , and Spongioarcinopsis . The phylogenetic analysis of ITS sequences shows that the isolates also form an independent branch. Different from other species, the isolate was found in a saline lake at a high altitude. The difference between the isolate and its sisters branch was that its cell wall was thin, and it was observed that many ellipsoid cells were connected head to tail, and it had one or more CBCs different from other species in the genus. At the same time, there was a branching structure on Helix-1. Given these morphological differences, phylogenetic analysis results, and comparison of ITS2 secondary structures, the isolate isolated in this study is proposed as a new species and named Pleurastrum gracilis sp. nov .

Eukaryotic algae are an important component of the soil microbial community. However, there is limited knowledge about the seasonal variations in the structure of soil algal communities and the correlations between different algal groups and soil environmental factors. Based on gene sequencing of the 18S rRNA V4 region, the changes in the community structure of eukaryotic algae in three different types of soil (sandy soil, forest soil and grassland soil along urban inland lake (Wuhan, China) coast) across four seasons were analyzed, and the correlations between the major taxonomic groups and environmental factors were examined. The annotated algae were ranked by abundance as follows: Chlorophyta, Bacillariophyta, Charophyta, Cryptista, Rhodophyta, Haptophyta and Glaucophyta. The top seven genera in terms of richness were: Chlamydomonas, Tetracystis, Chlorella, Chlorococcum, Coelastrum, Bracteacoccus and Desmodesmus. All soil samples tended to be neutral to alkaline. Environmental drivers for different groups were also explored. In terms of correlation, the environmental factors most related to Chlorophyta were total nitrogen, total phosphorus, and pH. Total nitrogen and water content were most related to Bacillariophyta and Charophyta. The seasonal differences in soil eukaryotic algal communities are more pronounced than the differences between soil types. Chlorophyta and Bacillariophyta are the two most abundant groups in different seasons and soil types. There is a significant difference in community composition between winter and other seasons.

SUMMARY: Soil algae are highly diverse and widely distributed, and play important roles in ecosystem. In the present study, two strains of green algae were obtained from the soil surface at Xiantao, Hubei and Xishuangbanna, Yunnan. Comparisons based on molecular sequencing and morphological observations revealed no differences between the two strains. The young cells are almost unicellular spherical, and the mature thalli comprise branched filaments, generally bilaterally branched, or sometimes unilaterally branched. A phylogenetic tree based on 18S rDNA and tufA cpDNA sequences showed that the isolates form a well‐supported independent branch and different from the nearest genera, Pseudendoclonium, Lithotrichon and Tellamia. Based on a combination of morphological similarities (distal cell aspect ratio, branched filaments and number of nuclei) and differences (habitat and vegetative cell diameter), we propose Luticula terrestris gen. et sp. nov. within Kornmanniaceae.

The genus Borodinellopsis is extremely rare and is the subject of limited research and reports. It currently comprises only two species, Borodinellopsis texensis and Borodinellopsis oleifera, which differ from other globose algae due to their unique centrally radiating chloroplasts. In this study, we describe a new specimen in detail based on morphological data and phylogenetic analysis and identify it as B. insignis. B. insignis and B. texensis exhibit a high degree of similarity, likely due to their shared characteristics of centrally radiating chloroplasts and flagella that are significantly longer than the cell body. A phylogenetic tree constructed based on the 18S rDNA sequence indicates that B. insignis and B. texensis form a branch that is distinct from other genera, such as Tetracystis, Spongiococcum, and Chlorococcum. Phylogenetic analysis of the ITS sequence, the rbcL gene, and the tufA gene reveals that B. insignis is significantly different from B. texensis, in that it has oil droplets, smaller vegetative cells and zoospores, and distinct habitats. It is also different from B.oleifera as it has smaller vegetative cells and zoospores, turns red after cultivation, has longer flagella, and resides in different habitats. The chloroplast genomes of B. texensis and B. insignis further show significant differences, with the phylogenetic tree constructed based on the analysis of 49 protein-coding genes forming two separate branches. The collinearity of the chloroplast genomes in B. texensis and B. insignis is poor, with 15 out of the 31 homologous modules displaying inversions and complex rearrangements. Given these differences, we classify this alga as a new species and named it Borodinellopsis insignis sp. nov.

There is only one species of Spongiosarcinopsis in the literature currently. It was found in gray soil in Russia for the first time. According to molecular data analysis results, the isolated algal strain is most closely related to Spongiosarcinopsis terrestris. Unlike Spongiosarcinopsis terrestris, the isolated strain was found on soil surfaces at high altitudes, the young vegetative cell is spherical, vegetative cells are relatively large, and pyrenoids are generally fewer. In view of such morphological differences, phylogenetic analysis results, and comparison of ITS2 secondary structure and ultrastructure, the strain isolated in the present study was proposed to be a novel species.

Ulvella species are widely distributed in ocean and freshwater habitats and from high latitudes to the tropics. However, no species of this genus have been found in the Qinghai–Tibetan Plateau. In the present study, five rock specimens were collected from the bottom of Qinghai Lake at a depth of about 15–28 m, from which three unialgal strains were isolated. These strains were characterized by prostrate pseudoparenchyma, irregular or radial branch filaments, and mono- or polystromatic discs or rosettes formed by consecutive filaments, with thalli that can grow up to 180 um in length, suggesting that they may be Ulvella species. Phylogenetic analysis based on 18S rDNA and tufA cpDNA sequences revealed that the isolates formed a strong branch among other Ulvella species and were closely related to Ulvella leptochaete and Ulvellawaernii. This result was also confirmed by neighbor-joining tree inference based on ITS2 secondary structure. Unlike other members of Ulvella, the isolated strain was characterized by its unique habitat, field morphology of thallus, size of vegetative cells, and number of pyrenoids. Based on these morphological differences, the phylogenetic analysis, and the comparison of ITS2 secondary structure with relative species, the strain isolated in this study was proposed to be a novel Ulvella sp. The alga was found on the bottom of brackish lakes on the Qinghai–Tibetan Plateau, which meant that our sampling range needed to be expanded further.