ABSTRACT During revision of the algal culture collection of the Institute of Botany (IBASU-A), Ukraine, some interesting strains of cyanobacteria were discovered, potentially representing new phylogenetic lineages at the genus rank. A polyphasic approach combining 16S rRNA gene phylogeny, percentage identity of 16S rRNA, 16S-23S ITS secondary structures, morphological and ultrastructural analyses was used to describe (according to the International Code of Nomenclature for algae, fungi and plants) two new taxa: Carminoleptolyngbya arenaria gen. et sp. nov. (Leptolyngbyales, Leptolyngbyaceae) and Kondratevia charkoviensis gen. et sp. nov. (Oscillatoriales, Microcoleaceae). These cultures had been obtained from terrestrial habitats of Germany (Baltic sand dunes) and Ukraine (cretaceous outcrops of Kharkiv region) respectively. C. arenaria has a Leptolyngbya-like morphology: thin, tortuous, greyish-pinkish trichomes, constricted and granulated at the cross-walls, with elongated cells and delicate sheaths, forming a film of carmine (=crimson-red) colour on the agar surface. TEM showed parietal parallel thylakoids typical of Leptolyngbyales and Oculatellales. This strain forms a well-supported lineage within Leptolyngbyales together with several strains identified as Leptolyngbya and Pseudanabaena from freshwater and terrestrial habitats of Europe and Asia, that might represent other unknown species of Carminoleptolyngbya. Phylogenetic analysis placed this taxon within Leptolyngbyaceae with Stenomitos as closest relative. K. charkoviensis has a Microcoleus- or Phormidium-like morphology: trichomes straight, cylindrical, slightly constricted at the cross-walls, tapered and curved at the ends, sheath firm, hyaline or yellowish, with elongated, conical-rounded and bent terminal cells. This strain forms a well-supported lineage within Oscillatoriales, Microcoleaceae with Kamptonema, Tychonema, Microcoleus and Microcoleusiopsis as closest relatives. TEM showed waved parallel thylakoids located near cell walls and within the cell which is typical for Oscillatoriales. Our data confirm that many undiscovered cyanobacteria still exist not only in terrestrial habitats, but also in algal culture collections.

ABSTRACT Cyanobacteria are an ancient and diverse group of oxyphototrophic bacteria found across a wide range of environments. The taxonomic diversity of terrestrial cyanobacteria inhabiting rock surfaces remains poorly studied despite their key role as pioneering species in ecological succession. We isolated two phycoerythrin-rich strains resembling the genus Leptolyngbya in a survey of filamentous cyanobacteria from previously unstudied epilithic habitats on the Suomenlinna Fortress (UNESCO World Heritage site) in Finland. We employed a comprehensive polyphasic approach to characterize these isolates to account for the known polyphyletic nature of Leptolyngbya and the presence of cryptic taxa. Our analyses revealed that the two strains form a distinct and well-supported clade within the family Leptolyngbyaceae. Therefore, we propose a new monospecific genus, Sivoneniella, following the International Code of Nomenclature for Algae, Fungi, and Plants. Secondary structures of conserved 16S–23S ITS regions (D1–D1’, box B and V3 helices), ITS per cent dissimilarity, multi-locus phylogenies (16S rRNA, rbcLX, rpoC1), and genome-based phylogenomic analyses all support the recognition of this novel cryptic genus. Genome mining and LC-MS analyses revealed the absence of known cyanotoxins in both strains (UHCC 1019T and UHCC 1020), and their cell extracts exhibited no inhibitory effects on the growth of relevant pathogenic bacteria and fungi. These findings advance our understanding of cyanobacterial diversity in terrestrial ecosystems, support the establishment of Sivoneniella as a new genus within the order Leptolyngbyales and explore the biotechnological potential of phycoerythrin-rich strains of S. epilithica.

ABSTRACT This study evaluates the diversity and distribution of species of the genus Halosaccion along the Russian Pacific coast using morphological data and molecular analyses. Halosaccion minjaii was found to be genetically distant from other species in the genus; this and its unique morphological features – namely the development of tetrasporangia in elevated sori between long sterile filaments (which are much longer than tetrasporangia) and the mode of spermatangia formation – led to the proposal of a new genus, Nothohalosaccion, with a single species N. minjaii. Data on species distribution in the north-western Pacific were refined. Halosaccion americanum was recorded for the first time in the Okhotsk Sea. This extended the species range north-westward. In contrast, the distribution of Halosaccion microsporum was restricted to northern and western parts of the Okhotsk Sea, the eastern Kamchatka coast and western Bering Sea. The distribution patterns of species of the genera Halosaccion and Nothohalosaccion are discussed in relation to the oceanography of the region. Types of the names H. microsporum, Dumontia hydrophora (≡ Halosaccion hydrophorum) and Ulva glandiformis (≡ Halosaccion glandiforme) are designated to guarantee their unambiguous use and to stabilize the nomenclature.

ABSTRACT Since the late 19th century, studies of the genus Porphyra sensu lato (Bangiales, Rhodophyta) have revealed a broad spectrum of life history strategies and reproductive modes. These variations are often interpreted as adaptive responses to the selective pressures imposed by spatially and temporally heterogeneous environments. However, the dynamics and prevalence of sexual versus asexual reproduction in natural populations remain poorly understood and insufficiently documented. In this study, we investigated the spatio-temporal variation in reproductive strategies of Porphyra umbilicalis, an emerging target species for aquaculture in the Northeast Atlantic, across a broad European range. Through microscopic examination and tracking the germination of spores released from fertile individuals in multiple populations, four main patterns were identified: (1) clear geographic structuring of reproductive strategies, with asexual reproduction prevailing in the Southern Bight of the North Sea and English Channel, and sexual populations more common in the South European Atlantic Shelf and Celtic Seas; (2) persistent dominance of asexual reproduction in populations with mixed reproductive modes, with a seasonal increase in the frequency of sexually reproductive individuals during winter; (3) microhabitat partitioning within the high intertidal zone, with asexual individuals occupying uppermost elevations and sexual individuals concentrated below, indicating ecologically driven niche differentiation; and (4) no consistent link between thallus size and reproductive mode, although sexual individuals were significantly larger during winter and spring. Collectively, these findings illustrate how environmental gradients shape reproductive strategies in P. umbilicalis, and suggest that asexuality may confer adaptive advantages in marginal intertidal zones.

ABSTRACT Green synthesis of nanoparticles is a potentially valuable technique for the pharmaceutical industry. The purpose of our research was to assess the in vitro antimicrobial and antidiabetic activity of silver nanoparticles synthesized using an aqueous extract of Sargassum tenerrimum. We confirmed that the aqueous extract of S. tenerrimum can fabricate silver nanoparticles. The nanoparticles were characterized using UV-Visible spectroscopy, Fourier Transform Infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), EDAX (Electron Dispersive Spectroscopy) and X-ray diffraction. The dark brown silver nanoparticles showed absorbance at 440 nm confirming nano-formulation. The FTIR spectrum identified the functional groups and absorption peaks, while the nanoparticles in SEM were 19.0 ± 5.4 nm in size with a smooth surface. The nanoparticles showed antimicrobial effects against pathogenic microorganisms (Gram-negative Pseudomonas aeruginosa and Escherichia coli and Gram-positive Bacillus cereus and Staphylococcus aureus) with Minimum Inhibitory Concentrations (MIC) of 72.2, 72.2, 64.6 and 57 µg, respectively. The nanoparticles were biocompatible and non-toxic and exhibited a dose-dependent glucose uptake in L6 myoblast cells, with 2.94 µg ml‒1 resulting in >50% uptake. The nanoparticles increased the expression of GLUT4 at low concentrations. Thus, silver nanoparticles synthesized from S. tenerrimum aqueous extract should be studied in vivo to explore their potential as a pharmaceutical agent.

ABSTRACT Flexiramia flexilis gen. et sp. nov. a new epilithic and rheophilic (fast-flowing water adapted) chlorophyte from subtropical Chinese rivers, is proposed based on integrative morphology, ultrastructure, and molecular phylogeny (18S rDNA, ITS2, tufA). Phylogenetic analyses robustly place this taxon within the Stephanosphaerinia clade (Chlamydomonadales), forming a sister lineage to Spongiosarcinopsis. The alga exhibits: (1) irregularly curved and branched filaments with cell walls continuous along the main axis, without any septation, (2) a parietal chloroplast containing a pyrenoid with tubular invaginations and (3) asexual reproduction via biflagellate zoospores showing unidirectional germination. Flexiramia differs from Spongiosarcinopsis and other related genera by its filamentous growth (vs. unicellular/sarcinoid), tubular pyrenoid invaginations (vs. penetrated by straight/curved thylakoids) and rheophilic adaptation (vs. terrestrial/planktonic habitats). This discovery expands the known ecological and morphological diversity of the Stephanosphaerinia clade, revealing evolutionary transitions towards filamentous growth and specialized pyrenoid ultrastructure in freshwater chlorophytes.

ABSTRACT Microalgae are increasingly attractive to the nutraceutical industry due to their rich content of omega fatty acids, carotenoids, lipids and other bioactive compounds. However, soil microalgae remain underutilized for their nutraceutical potential. This study evaluates the nutritional composition and potential food applications of seven soil green microalgae isolated from forest ecosystems in southern Kerala, India. Biochemical analyses assessed total protein, carbohydrate content, bioactive compounds and essential micro- and macronutrients. Protein content ranged from 4.06 ± 0.31 to 14.33 ± 0.27 mg g‒1 dry weight, while carbohydrates varied from 10.58 ± 0.53 to 160.46 ± 4.70 mg g‒1 dry weight. ICP-MS analysis confirmed the presence of essential nutrients, supporting their use in dietary supplementation. GC-MS profiling identified unsaturated fatty acids, including omega-6 and omega-3 fatty acids, along with other essential fatty acids and bioactive compounds. Chlorococcum sp. and Chlorolobion sp. have been the subject of previous studies, but all other soil algae are reported for the first time in terms of their nutritional composition and bioactive potential. These findings highlight the untapped potential of terrestrial green microalgae as sustainable and nutrient-rich alternatives for functional food and nutraceutical applications, particularly in addressing global malnutrition and food security challenges.

ABSTRACT In cytokinesis of brown algae, the site at which microtubules (MTs) extending from centrosomes attached to daughter nuclei following nuclear division cross each other develops into a future division plane. An actin plate appears at this site, and a new cell partition membrane is formed. Cytokinesis progresses with outgrowth of the new cell partition membrane and not by ingrowth of furrows in the plasma membrane. The cytokinesis apparatus, composed of MTs and an actin plate, is thought to be involved in vesicle transport, accumulation and fusion to form a new cell partition membrane at the division plane; however, it remains unclear how they interact with each other to promote cytokinesis. To understand the relationship between the cytoskeleton and development of a new cell partition membrane, the behaviour of the cytoskeleton was observed during cytokinesis in living subapical cells of Sphacelaria rigidula by injecting fluorescently labelled phalloidin, actin or tubulin, and staining membranous structures with FM4-64FX. Double staining with Alexa Fluor 488-phalloidin and FM4-64FX revealed that the starting point of formation of a new cell partition membrane corresponded to the position where the actin plate would appear, and both expanded simultaneously, as observed in our previous studies. Cells injected with rhodamine-conjugated actin and HiLyte Fluor 488-conjugated tubulin showed a region of concentrated MTs extending from each centrosome, which appeared to be associated with the initiation of actin plate formation. The areas of the concentrated MTs changed with expansion of the actin plate. Double staining with HiLyte Fluor 488-conjugated tubulin and FM4-64FX revealed that MTs extended towards the edge of the new cell partition membrane. Although it was not possible to observe all three simultaneously, MTs were likely involved in the formation and expansion of the actin plate, and actin was involved in the new cell partition membrane formation.

ABSTRACT Some Ulvophyceae are cryptic due to their morphological plasticity and lack of distinct traits. Consequently, molecular approaches such as DNA barcoding and metabarcoding are essential for accurate species discrimination. Large parts of the African coastline remain understudied in this respect. In this study, Ulvophyceae were collected from various substrates at 24 coastal sites along the Senegalese coast. DNA barcoding targeting the tufA gene and metabarcoding targeting the rbcL gene were applied to these samples. Most of the sequences obtained represented four species (Ulva lactuca, U. compressa, Codium decorticatum and C. isthmocladum) already reported in Senegalese species inventories. However, the molecular assessment also confirmed the presence of U. ohnoi (described from Japan), U. tepida (distributed in the Indo-Pacific), U. chaugulei (previously reported from India, Iran, Israel, China and Brazil), Chaetomorpha valida (described from Tasmania, Australia), and a specimen similar in rbcL sequence to several Ulva species originating from New Caledonia, French Polynesia, India and China, i.e. South Pacific, Indian Ocean and South China Sea. Additionally, the Mediterranean species Bryopsis muscosa has reached Senegal. Morphological identification also suggested the presence of Caulerpa chemnitzia var. turbinata and Caulerpa chemnitzia var. laetevirens in West Africa. The challenges of morphological identification, particularly for Ulvophyceae, are evident, emphasizing the necessity of molecular data for accurate species discrimination. The detection of previously unrecorded species raises questions about whether their presence in Senegal results from global change, such as climate shifts and increased maritime transport, or the limitations of past morphological inventories. Further investigations should focus on clarifying the taxonomy of key genera (Cladophora, Caulerpa, Bryopsis, Codium and Chaetomorpha) through broader sampling and the application of advanced molecular markers to better understand Senegal’s Ulvophyceae biodiversity and facilitate monitoring future changes in species composition due to environmental shifts or anthropogenic pressures.

ABSTRACT The area around the CIIMAR building, at the Porto de Leixões Cruise Terminal on the northern Portuguese coast, is a hub for cyanobacterial diversity due to its continuous maritime traffic. This makes the site ideal for uncovering new taxa and documenting already known species. Terrestrial cyanobacteria are underexplored in the northern Portugal coast: here we describe four new species and report on cyanobacterial diversity around the CIIMAR building. The study is based on a polyphasic analysis of 13 isolates, belonging to seven genera in the orders Leptolyngbyales (1 strain), Desertifilales (1), Oculatellales (1), Oscillatoriales (2), Chroococcidiopsidales (3), Geitlerinematales (1) and Nostocales (4). Among these, four were classified as new species in the genera Aliterella, Gloeocapsopsis, Compactococcus and Desertifilum. Additionally, the species Desertifilum salkalinema, D. fontinale and D. dzianense were synonymized with the type D. tharense. The isolate LEGE 221420 has a parietal and/or fascicular arrangement of thylakoids, unprecedented in cyanobacteria, confirming that this character is unstable and cannot serve as a taxonomic marker at the genus level.