Journal Of Phycology[JOURNAL]
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200 papers
Re-isolation of Gonyaulax hyalina from the type locality in the Gulf of Aden: Integrated analysis of morphological, molecular, and toxicological characteristics.
Chirdon MA, Mertens KN, Bilien G … +10 more , Derrien A, Nguyen-Ngoc L, Doan-Nhu H, Shin HH, Li Z, Gu H, Ahmed MM, Hess P, Awaleh MO, Ibrahim NH
J Phycol · 2025 Oct · PMID 40884281 · Publisher ↗
This study provides a comprehensive investigation of Gonyaulax hyalina, integrating morphological, phylogenetic, and toxicological approaches. Strains were re-isolated from its type locality in the Gulf of Aden (western...
This study provides a comprehensive investigation of Gonyaulax hyalina, integrating morphological, phylogenetic, and toxicological approaches. Strains were re-isolated from its type locality in the Gulf of Aden (western Indian Ocean) 124 years after its original description by Ostenfeld and Schmidt (1901, p. 141), along with additional Pacific strains collected from Korea and Viet Nam. The primary objective was to clarify the taxonomy of G. hyalina, which has frequently been confused with the morphologically similar G. fragilis. Morphological and molecular data confirmed that the Indo-Pacific strains examined belong to G. hyalina. Diagnostic morphological features supporting this identification included the presence of a characteristic surface ornamentation, a distinct anterior intercalary plate 1a, and comparatively smaller cell dimensions. Phylogenetic analyses based on LSU and SSU rRNA gene sequences revealed that these strains formed a distinct clade, separate from existing G. hyalina sequences in GenBank. This phylogenetic analyses indicated the presence of two ribotypes (A and B) within the species, although morphological characters do not reflect this, providing evidence of cryptic speciation in G. hyalina. Ribotype B corresponded to strains previously associated with gelatinous mucilage aggregates, known from the Mediterranean and New Zealand coastal waters. Toxicological assays conducted on strain DJ_I3 from the Gulf of Aden showed no detectable toxin production. Lastly, analysis of seasonal dynamics in the Gulf of Aden demonstrated that G. hyalina is present throughout the year, with abundance peaking in summer and declining markedly during winter months.
Mitochondrial mRNA oligocitydylation occurs in Chlorophyceae and Ulvales but not Bryopsidales or Trebouxiophyceae.
Cahoon AB, Maggard IJ, Pathan WN
J Phycol · 2025 Oct · PMID 40875506 · Full text
Mitochondrial mRNAs in the green algal class Chlorophyceae have non-template 3' oligo-cytosine-rich additions, also known as oligo(C), polycitydylation, or poly(C) "tails." These oligonucleotide additions are believed to...
Mitochondrial mRNAs in the green algal class Chlorophyceae have non-template 3' oligo-cytosine-rich additions, also known as oligo(C), polycitydylation, or poly(C) "tails." These oligonucleotide additions are believed to be unique to green algal mitochondria, as none have been observed in any other organism. Among algae, oligocitydylation had only been observed in species within the Chlorophyceae, with no evidence of it occurring in other taxonomic classes. In this study, evidence is presented that mitochondrial mRNA oligocitydylation occurs in the genus Ulva, demonstrating its presence in the Class Ulvophyceae and Order Ulvales. Two other species in Ulvophyceae, Bryopsis plumosa and Codium fragile, from the Order Bryopsidales were also screened, but no evidence of oligonucleotide additions was observed. This demonstrates that oligocitydylation occurs in Ulvophyceae but suggests it may be limited to the Ulvales. Three species from Trebouxiophyceae were also screened, and there was no evidence of oligonucleotide additions, suggesting it does not occur in this clade. These results demonstrate that oligocitydylation does occur outside of the Chlorophyceae but only in the closely related Ulvales clade, suggesting this could be a biochemical synapomorphy shared by these groups.
Type-assisted taxonomy and biogeography of Corallina (Corallinales, Rhodophyta) in the eastern Pacific: Corallina americana sp. nov., C. bathybentha, C. hommersandiorum sp. nov., and C. saundersii sp. nov.
Wade RM, Ogushi R, Gabrielson PW … +5 more , Hind KR, Hughey JR, Lindstrom SC, Miller KA, Martone PT
J Phycol · 2025 Oct · PMID 40864172 · Publisher ↗
The articulated coralline genus Corallina is common in temperate rocky ecosystems and provides settlement substrate and refugia for other organisms. However, our ability to understand species-specific traits and interact...
The articulated coralline genus Corallina is common in temperate rocky ecosystems and provides settlement substrate and refugia for other organisms. However, our ability to understand species-specific traits and interactions has been confounded by overlapping morphological characteristics among species. DNA sequences from type specimens and recently collected specimens have begun to address these issues by clarifying phylogenetic species boundaries and geographic distributions. We sequenced an rbcL gene barcode from a paratype specimen of Corallina bathybentha (type locality: 0.5 miles south of the west end of Anacapa Is., California, United States) and have provided an updated description. Three cryptic species have been described: C. hommersandiorum and C. saundersii are endemic to the northeastern Pacific, whereas C. americana is anti-tropical in the eastern Pacific. Haplotype network analyses using the COI locus suggested that C. americana naturally dispersed from North to South America; it was not likely a recent or human-mediated introduction. To explore species boundaries, stepwise discriminant models were used to analyze morphological and ecological traits and were visualized in canonical multidimensional plots. Every species overlapped in canonical space with at least one other species, further illustrating that morphological identifications of Corallina species are challenging and unreliable. This work completes the taxonomic study of the currently known diversity of Corallina in the northeast Pacific for which we have access to type specimens. Given that this region is likely the center of origin and home to three-quarters of the known Corallina species, these taxonomic studies, including this one, make a significant contribution to our understanding of coralline diversity.
Using computational fluid dynamics to assess trait functions of life at low Reynolds numbers.
Mohan J, Mohan JA, Saros JE
J Phycol · 2025 Oct · PMID 40862323 · Publisher ↗
We applied computational fluid dynamic simulations to three-dimensional (3D) computer models of diatoms to assess the effect of trait functions on niche space without the confounding influence of correlated traits. Sinki...
We applied computational fluid dynamic simulations to three-dimensional (3D) computer models of diatoms to assess the effect of trait functions on niche space without the confounding influence of correlated traits. Sinking behavior of phytoplankton was assessed via computer-simulated experiments to test the physics of life at low Reynolds numbers. Specifically, 3D models of Stephanodiscus niagarae were constructed across the middle of the species size range and were placed in simulations to assess variance in the sinking and acceleration rates of the cells. First, we simulated models of anatomically correct cells as a control group. To assess trait function, in this case the function of the spines that encompass the outer rim of each frustule (cell wall), simulations of the model were rerun under the same conditions with the trait removed from the model as the experimental group. We observed that spines served to reduce the influence of outside forces on the cell, specifically the force of gravity, by reducing the sinking and acceleration rates of spined versus spineless models. We also observed that spines increased the range of sinking rates, which increased the dispersal of a population by increasing the range of responses to turbulence. When Hutchinson (1961) presented the paradox of plankton, there was a caveat "it is hard to believe that in turbulent open water many physical opportunities for niche-diversification exist" (p. 141). Herein we have shown that many opportunities for niche diversification are tied to a single trait. By testing trait function in fluid dynamic simulations, we can examine global trends in biodiversity.
Hulburtia sanyaensis gen. et sp. nov., a sand-dwelling dinoflagellate from the South China Sea, and ultrastructure of Pseudocochlodinium profundisulcus and Grammatodinium tongyeonginum.
Gu H, Huang S, Huang S … +6 more , Wang L, Mertens KN, Leaw CP, Lim PT, Kuwata K, Iwataki M
J Phycol · 2025 Oct · PMID 40856472 · Publisher ↗
Athecate dinoflagellates have a complex evolutionary history and are considered paraphyletic. Phylogenetic relationships among athecate dinoflagellate species and their higher taxonomic levels remain far from resolved. I...
Athecate dinoflagellates have a complex evolutionary history and are considered paraphyletic. Phylogenetic relationships among athecate dinoflagellate species and their higher taxonomic levels remain far from resolved. In the present study, six strains of athecate dinoflagellates were established by isolating single cells or cysts from the South China Sea. Both morphology and ultrastructure were examined in detail, and ribosomal DNA sequences were obtained. Two sand-dwelling strains were assigned to Hulburtia sanyaensis gen. et sp. nov., characterized by a dominant non-motile stage and a semicircular apical structure complex (ASC). Asexual reproduction occurred through binary fission during the immotile phase and formed a cluster of up to 16 cells. The species was also recorded from Kagoshima, Japan. The other strains were identified as Pseudocochlodinium profundisulcus and Grammatodinium tongyeonginum. Nuclear chambers were observed in P. profundisulcus but not in the other two species. The Chinese G. tongyeonginum shared 96.37% sequence similarity in the SSU rDNA region with specimens from South Korea. The molecular phylogeny was inferred using maximum likelihood and Bayesian inference based on concatenated sequences of the SSU, ITS, and LSU rDNA regions. Pseudocochlodinium profundisulcus was nested within Gymnodiniales sensu stricto, while H. sanyaensis and G. tongyeonginum were positioned distantly from this group. The genera Hulburtia and Grammatodinium were closely related to the fossil thecate dinoflagellate Dapsilidinium, but their higher taxonomic ranks remain to be determined. Our results highlight the underestimation of athecate dinoflagellate diversity and emphasize the significance of ultrastructure characteristics to understand their evolution.
Long lifespan and substantial biomass production support stable high biomass of Ascophyllum nodosum under interannual climate fluctuations in Greenland.
Olesen B, Marbà N, Duarte CM … +1 more , Krause-Jensen D
J Phycol · 2025 Oct · PMID 40852971 · Full text
The brown macroalga Ascophyllum nodosum is a foundation species on intertidal rocky shores, where its perennial canopy and high productivity support key ecological functions. However, its population dynamics near the nor...
The brown macroalga Ascophyllum nodosum is a foundation species on intertidal rocky shores, where its perennial canopy and high productivity support key ecological functions. However, its population dynamics near the northern edge, where low temperatures and sea ice may challenge stability, are largely unknown. We followed the population structure, dynamics, and nutrient status of A. nodosum in the sheltered, subarctic Kobbefjord, Greenland from 2012 to 2019. Despite the northern location, population biomass (16-27 kg FW · m) was within the upper known range and was dominated by few large (max length: 109 cm), old individuals (observed age: up to 19 years; estimated mean lifespan: 37.5 years based on intrinsic mortality rate). Population density remained stable because of low mortality (0.019 · year) and recruitment rates (0.010 · year), sustained by an understory of small juveniles. Biomass increased 1.5-fold over the 8-year study, supported by high biomass productivity (3.3-8.1 kg FW · m · year) that balanced branch loss and reflected a moderate biomass turnover time (2.6-6.3 years) of organic matter, underlying the apparent stability. Such overall population stability reflects a "biomass storer" strategy typical of environments with low disturbance and nutrient levels. The stability is remarkable given seasonal ice cover (2-7.5 months per year), large variation in average daily temperature (-3.9 to 15.4°C), and low nutrient supply. While ice breakup poses a risk of shoot abrasion, the ice cover likely provides protection against ice scouring. Enhanced growth during warmer summers and earlier ice break-up suggests faster turnover rates in the future to the extent nutrient availability can support it.
Palmelloid-like structure formation mechanism in Chlorella sorokiniana under ethanol stress.
Abate R, Liu C, Bi Y … +5 more , Mi W, Song G, Zhang Y, Kifle D, Yahui G
J Phycol · 2025 Oct · PMID 40852964 · Publisher ↗
Although the formation of "palmelloid-like" cells as a response to environmental stress has been sporadically reported in Chlorella sp., the association between morphological and molecular indices has been poorly underst...
Although the formation of "palmelloid-like" cells as a response to environmental stress has been sporadically reported in Chlorella sp., the association between morphological and molecular indices has been poorly understood. Hence, this study investigated the morphological and molecular effects of ethanol stress on C. sorokiniana by providing 0.0%, 0.025%, and 0.1% (v/v) ethanol. The results showed that cell growth, chlorophyll a, and photosynthetic efficiency were promoted under 0.025% ethanol. In contrast, the cells under 0.1% ethanol treatment were highly stressed; cell growth and physiological activities were inhibited, the content of cellular lipid, carbohydrate, reactive oxygen species, and the cell volume increased, and palmelloid-like structures with copious cell envelopes and higher cell wall carbohydrate contents were observed. The transcriptomic gene set enrichment analysis showed that chitin binding and organelle organization were upregulated while the developmental process was downregulated. Genes for actin-related-2, auxin-biding 1, phosphatidylinositol 4-kinase alpha1, phosphatidylinositol 4-phosphate 5-kinase 2 isoform A, and cytokinesis dedicator 4 were downregulated, whereas polysaccharide export, putative polygalacturonase, carbohydrate deacetylase, chitin, cellulose biosynthesis, and unsaturation of fatty acids were upregulated, implying polysaccharide was incorporated into the cell wall, and the rigidity of the cell membrane was promoted. These results suggest the suppression of the developmental process and cytokinesis and the overexpression of microtubules and cell-envelope genes could be the driving force for palmelloid-like structure formation, which could enhance the survival of cells under stress conditions by reducing cell surface area, promoting the production of protective cover and settleability, and adjusting cell rigidity.
Exploring cyanobacteria from the Andaman mangroves of Thailand: Descriptions of new species of Desertifilum, Roseofilum, Tigrinifilum, and Persinema using a polyphasic approach.
Ginn BLC, Praiboon J, Merican F … +4 more , Maneekat S, Zeng C, Zuccarello GC, Muangmai N
J Phycol · 2025 Oct · PMID 40852962 · Publisher ↗
Non-heterocytous filamentous cyanobacteria are increasingly recognized as abundant and diverse microbial components of tropical and subtropical mangrove ecosystems. However, taxonomic studies of cyanobacteria in Thailand...
Non-heterocytous filamentous cyanobacteria are increasingly recognized as abundant and diverse microbial components of tropical and subtropical mangrove ecosystems. However, taxonomic studies of cyanobacteria in Thailand have largely focused on freshwater and artificial hypersaline environments, leaving mangrove-associated cyanobacterial communities understudied. In this polyphasic study, cyanobacterial mats were isolated and characterized from mangrove environments along the Andaman coastlines of Ranong and Phang-Nga provinces. Comparative analysis of morphology, salinity tolerance, habitat preference, 16S rRNA gene phylogeny and genetic similarity, 16S-23S ITS rRNA region phylogeny, secondary structure and percent dissimilarity supported the descriptions of Desertifilum andamanense sp. nov., Tigrinifilum phangngense sp. nov., Roseofilum epilithicum sp. nov., and Persinema corticola sp. nov., while justifying the continued recognition of D. fontinale and D. tharense. Two divergent ITS rRNA region operons in T. floridanum with different leader motifs, D1-D1', and D2 regions proved to be useful diagnostic markers of the ITS rRNA region for species and strain differentiation within Tigrinifilum. Our results underscore the importance of a polyphasic approach that also considers intragenomic ITS rRNA region variation to ensure robust and accurate taxonomic assessments of cyanobacteria. This study also provides records of the genera Desertifilum, Roseofilum, Tigrinifilum, and Persinema in Thailand, contributing to a more comprehensive understanding of the nation's diversity and biogeography of cyanobacteria.
Molecular and cytomorphological characterization of Pseudanabaena vesniana sp. nov. and Pseudanabaena suomiensis var. macedonica var. nov. (Pseudanabaenales, Cyanobacteriota) with evidence of microcystin-producing Pseudanabaena taxa.
Aleksovski B, Saraf A, Stefanoska E … +6 more , Kiprijanovska S, Vuchurević A, Pakovski K, Dimovski A, Gugger M, Krstić S
J Phycol · 2025 Oct · PMID 40810679 · Publisher ↗
Detailed molecular and cytomorphological characterization of two toxic Pseudanabaena strains (NMCCC 011 and NMCCC 012), isolated from highly polluted shallow areas of Monospitovo Marsh (North Macedonia), was performed us...
Detailed molecular and cytomorphological characterization of two toxic Pseudanabaena strains (NMCCC 011 and NMCCC 012), isolated from highly polluted shallow areas of Monospitovo Marsh (North Macedonia), was performed using a "polyphasic" approach. This involved morphological and ultrastructural characterization, phylogenetic assessment of the 16S rRNA gene, analyses of the 16S-23S internal transcribed spacer (ITS) rRNA region, and investigations of the mcyB gene. The 16S rRNA gene phylogenetic analysis and the ITS rRNA region analyses confirmed that strain NMCCC 011 was a novel species for which we have proposed the name Pseudanabaena vesniana sp. nov., whereas NMCCC 012 represented a novel variety of Pseudanabaena suomiensis, here designated as P. suomiensis var. macedonica. The overall 16S rRNA gene phylogenetic analysis grouped Pseudanabaena into four large clades. Two of them comprised the primary lineages of diversification, hosting most Pseudanabaena sensu stricto infrageneric units. Most of these units formed distinctly recognizable subclades corresponding to different Pseudanabaena species (Cyanobacteriota); however, some strains were misidentified, leading to several scattered species through different subclades within the genus. Additionally, the genus Pseudanabaena was determined to be polyphyletic, with some strains clustering within the genera Tumidithrix and Thalassoporum (Cyanobacteriota). The 16S rRNA gene sequence identity within Pseudanabaena sensu stricto ranged from 95.7% to 99.9%, while the identity with Tumidithrix, Thalassoporum, and Thermostichus (Cyanobacteriota) ranged from 87.6% to 92.0%. Furthermore, both strains NMCCC 011 and NMCCC 012 produced microcystins and 2-methylisoborneol. The production of microcystins was confirmed by genetic and enzyme-linked immunosorbent assay (ELISA) analyses. Through this study, we report the presence of the mcyB gene in Pseudanabaena.
A genetic transformation system for the heterotrophic diatom Nitzschia putrida (Bacillariophyceae).
Deng L, Li Y, Tanizawa Y … +4 more , Nakamura Y, Kamikawa R, Hopes A, Mock T
J Phycol · 2025 Oct · PMID 40810677 · Full text
Diatoms are important primary producers in aquatic ecosystems. Most of them are photoautotrophs and have evolved to thrive under diverse environmental conditions from the poles to the tropics. However, some diatom specie...
Diatoms are important primary producers in aquatic ecosystems. Most of them are photoautotrophs and have evolved to thrive under diverse environmental conditions from the poles to the tropics. However, some diatom species such as Nitzschia putrida have lost photosynthesis and have therefore become free-living secondary heterotrophs. Thus, these diatoms provide unique opportunities to study the evolutionary processes required to thrive without photosynthesis and independent of a resource-providing host. They may also provide a chassis for reverse engineering photosynthesis in eukaryotic organisms. Here, we have developed a genetic transformation system for N. putrida using a biolistic approach. By leveraging genome and transcriptome data, we identified the nicotinamide adenine dinucleotide hydride (NADH)-ubiquinone reductase complex 1 promoter as a robust candidate for driving transgene expression. Through Golden Gate Cloning, we engineered plasmids, including the selectable marker nourseothricin and the reporter eGFP. An evaluation of transformation efficiency confirmed the successful integration and expression of the transgenes. Fluorescence microscopy demonstrated the expression of eGFP in the transformed cell lines, which retained a growth phenotype similar to that of the wild type cells. Thus, our work in combination with the available genome and transcriptome of N. putrida enables reverse genetics with a free-living secondary heterotroph.
Implications of the finding of a new member of brown algae in freshwaters for biodiversity and the transition from marine to freshwater environment.
Necchi O
J Phycol · 2025 Aug · PMID 40808596 · Publisher ↗
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Flow cytometry and holotomography illuminated the relationship between iron availability and the growth and cellular development of Symbiodinium sp.
Gu H
J Phycol · 2025 Aug · PMID 40808591 · Publisher ↗
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Assessment of rhodolith-forming species diversity in British Columbia uncovers novel cryptic diversity in the genera Boreolithothamnion and Rhodolithia gen. nov. (Florideophyceae, Rhodophyta) and the occurrence of hybrid rhodoliths.
Taylor KE, Saunders GW
J Phycol · 2025 Oct · PMID 40801815 · Full text
Rhodolith collections in British Columbia have historically been limited, and published regional species diversity data are poor. The acquisition of recent collections, notably from rhodolith beds in Haida Gwaii, provide...
Rhodolith collections in British Columbia have historically been limited, and published regional species diversity data are poor. The acquisition of recent collections, notably from rhodolith beds in Haida Gwaii, provided an opportunity to assess diversity in these waters. The DNA barcode markers COI-5P, rbcL-3P, and psbA were used to identify unique genetic groups, which were then placed into a phylogenetic context with other coralline algae and subsequently observed anatomically. These analyses uncovered six rhodolith-forming species: two known, viz. Boreolithothamnion phymatodeum and Boreolithothamnion soriferum; a species provisionally called Boreolithothamnion sp. 1heterocladum; and three novel species described here, viz. Boreolithothamion astragaloi sp. nov., Boreolithothamnion tanuense sp. nov., and Rhodolithia gracilis gen. et. sp. nov., which comprises three varieties. Of particular interest, sequences of the ITS rDNA region showed the variety Rhodolithia gracilis var. gracilis × ramosa var. nov. to be a hybrid of the other two varieties: Rhodolithia gracilis var. gracilis var. nov. and Rhodolithia gracilis var. ramosa var. nov. Although understanding the full extent of BC rhodolith beds will require additional sampling, these findings indicate that rhodoliths are widespread and diverse in British Columbia.
Biochemical characterization of phosphoenolpyruvate carboxykinases from multiple species of brown algae.
Jin JQ, Yokooji Y, Shibata T … +1 more , Atomi H
J Phycol · 2025 Oct · PMID 40801810 · Full text
Phosphoenolpyruvate carboxykinase (PEPCK) is involved in the conversion of phosphoenolpyruvate (PEP) to oxaloacetate (OAA). In addition to playing a role in gluconeogenesis in various organisms, PEPCK also functions in t...
Phosphoenolpyruvate carboxykinase (PEPCK) is involved in the conversion of phosphoenolpyruvate (PEP) to oxaloacetate (OAA). In addition to playing a role in gluconeogenesis in various organisms, PEPCK also functions in the C cycle to concentrate CO for photosynthesis in some C plants. Brown algae harbor genes related to the C cycle, including the PEPCK gene, and are proposed to employ a C cycle-like pathway. However, little is known about the CO-concentrating mechanisms and the properties of the enzymes involved in brown algae. Here, we obtained soluble recombinant PEPCKs of five brown algae and carried out biochemical analyses. The five PEPCKs were ATP-dependent and displayed similar or higher specific activities compared with their counterparts from other organisms. Phosphoenolpyruvate carboxykinase from Ishige okamurae (Io-PEPCK) exhibited the highest specific activity in both carboxylation and decarboxylation directions, with values of 48.4 and 63.3 μmol · min · mg, respectively. Additionally, Io-PEPCK displayed a k/K value of 9.2 × 10 · M · s, much higher than those of previously characterized PEPCKs. The response of PEPCK activity to various metabolites showed that citrate and malate inhibited the carboxylation but promoted the decarboxylation activity of Io-PEPCK. Various ATP concentrations resulted in different degrees of inhibition on the carboxylation activity of PEPCK, suggesting that ATP concentration potentially regulates PEPCK activity in brown algae. The analysis of cell extracts from I. okamurae suggested that PEPCK rather than PEPC dominates the carboxylation in this brown alga. Based on previous knowledge and the results presented here, a model for a C cycle-like pathway in brown algae has been proposed.
De novo transcriptome of the red alga Gracilariopsis tenuifrons (Gracilariales, Rhodophyta) in response to prolonged temperature stress.
Faria AVF, Godfroy O, Cock JM … +1 more , Plastino EM
J Phycol · 2025 Oct · PMID 40788061 · Publisher ↗
Transcriptomic information is still scarce for seaweeds, especially for species from tropical regions. Laboratory-based physiological studies of some red algae have shown that they can tolerate temperatures that exceed t...
Transcriptomic information is still scarce for seaweeds, especially for species from tropical regions. Laboratory-based physiological studies of some red algae have shown that they can tolerate temperatures that exceed those observed in their natural conditions. To understand the molecular mechanisms related to this tolerance, we chose as a model the agarophyte red alga Gracilariopsis tenuifrons and analyzed transcriptomic profiles at two different temperatures: 25°C (control temperature) and 33°C (stress temperature). Under the stress temperature conditions, only a relatively small percentage of genes were differentially expressed compared to the control temperature (5.75% were down-regulated and 5.25% were up-regulated at 33°C). Analysis of the predicted functions of the differentially regulated genes indicated enrichment in DNA-associated processes for the up-regulated genes and enrichment in gene ontogeny categories related to photosynthesis and membrane-associated processes for the down-regulated genes. The de novo transcriptome data provided in this study is a valuable scientific resource for future comparative research on red algae at stress conditions.
Expanding our knowledge of Synurales (Chrysophyceae) in Florida, United States: Proposing three novel Mallomonas taxa.
Knotek P, Pusztai M, Jadrná I … +1 more , Škaloud P
J Phycol · 2025 Oct · PMID 40728039 · Full text
We conducted a survey of Synurales diversity in Florida (United States), focusing on two established hotspots-Ocala National Forest and Myakka River State Park-and two previously unexplored sites-Manatee Lake and Lake Le...
We conducted a survey of Synurales diversity in Florida (United States), focusing on two established hotspots-Ocala National Forest and Myakka River State Park-and two previously unexplored sites-Manatee Lake and Lake Lee. Using transmission electron microscopy (TEM), we identified 69 species, increasing the total number recorded from Florida to 90. Among these, three species-Mallomonas cornea sp. nov., M. laureana sp. nov., and M. joergenii sp. nov.-have been newly described based on detailed morphological and molecular analyses. We have also proposed a new combination, M. poseidonii comb. et stat. nov., and established a new section, Corneae sect. nov., based on molecular phylogenetics. Our findings revealed an independent emergence of ribbed scale shield ornamentation in M. joergenii sp. nov. and suggested that internal scale reticulation in M. laureana sp. nov. may be an adaptation to high UV irradiance in tropical environments. This study underscores the value of DNA sequence data in resolving taxonomic ambiguities, elucidating evolutionary patterns, and enhancing species recovery from type localities.
Molecular characterization of the type species of Kyrtuthrix (Rivulariaceae, Cyanobacteriota) with comparison to Nunduva: Morphologically different but molecularly cryptic genera.
Vondrášková A, Hauer T, Mareš J … +5 more , Berrendero-Gomez E, Zima J, Montoya-Terreros H, Villanueva CD, Johansen JR
J Phycol · 2025 Oct · PMID 40719612 · Full text
The euendolithic genus Kyrtuthrix was originally described in 1929 by A. Ercegović from the Dalmatian coast. Due to its isopolar filaments, Kyrtuthrix was classified within the cyanobacterial system as part of the family...
The euendolithic genus Kyrtuthrix was originally described in 1929 by A. Ercegović from the Dalmatian coast. Due to its isopolar filaments, Kyrtuthrix was classified within the cyanobacterial system as part of the family Scytonemataceae, even though trichomes tapering toward their ends represent a feature typical of the family Rivulariaceae. In the last decade, four new species of Kyrtuthrix have been described. Their sequences helped to establish Kyrtuthrix as belonging to the family Rivulariaceae. However, the new species demonstrated that Kyrtuthrix was not always euendolithic, as the new discoveries occurred on igneous rocks that were not susceptible to penetration by cyanobacteria. We were able to obtain sequences of the 16S rRNA gene, the 16S-23S ITS rRNA region, the rpoC1 gene, and rbcLX gene for phylogenetic analyses of two classical species of Kyrtuthrix-the type species K. dalmatica collected from the Dalmatian coast and K. maculans collected from the Pacific coast of Peru. Our analyses revealed that both taxa were related to the newly described Kyrtuthrix species, although they were not clearly separated by molecular character sets from the more recently described Nunduva. A third Kyrtuthrix species from the coast of France was characterized by us during this study but was intermediate in morphological structure and phylogeny between K. dalmatica and K. maculans and not given a specific epithet. If we relied on the 16S rRNA gene sequence evidence, Nunduva would have been collapsed into the older genus Kyrtuthrix. However, using multiple gene evidence, they formed sister clades and, therefore, have been treated as distinct genera in this manuscript.
Contribution of ornithine aminotransferase in proline metabolism response to high temperature in Gracilariopsis lemaneiformis (Rhodophyta).
Sun S, Yu X, Lu K … +2 more , Xu N, Sun X
J Phycol · 2025 Aug · PMID 40698915 · Publisher ↗
The seaweed Gracilariopsis lemaneiformis is used for agar and abalone feed, but high summer temperature in the southern oceans of China limits the cultivation industry. Therefore, enhancing the heat tolerance of G. leman...
The seaweed Gracilariopsis lemaneiformis is used for agar and abalone feed, but high summer temperature in the southern oceans of China limits the cultivation industry. Therefore, enhancing the heat tolerance of G. lemaneiformis is crucial for prolonging its growth period along with increasing production and economic performance. Proline, a key osmotic regulator, plays an essential role in stress responses, including drought, heat, cold, and high salinity. Here, we investigated the dynamic changes in proline accumulation and its metabolic enzymes response to high-temperature stress in G. lemaneiformis. Results showed that elevated temperatures significantly increased proline accumulation, stimulated the activities of its synthetases pyrroline-5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT), while concurrently suppressed the activity of its degrading enzyme proline dehydrogenase (ProDH). Pearson correlation analysis displayed a stronger positive association between proline level and OAT activity than with P5CS or pyrroline-5-carboxylate reductase (P5CR) activity, as well as a negative correlation with ProDH activity. Furthermore, exogenous 24-epibrassinolide, trehalose, and ornithine increased OAT activity or its gene transcription, while salicylic acid induced P5CS activity and P5CR2 transcriptional levels, which all resulted in the enhanced proline accumulation. Finally, bioinformatics analysis revealed that GlOAT contains a predicted PLP-binding domain, exhibits a high likelihood of mitochondrial localization, and shows a high degree of phylogenetic conservation. In summary, this study demonstrated that OAT is the critical enzyme involved in proline synthesis under high-temperature stress, which might provide a foundation for future transgenic breeding to improve high-temperature tolerance in G. lemaneiformis.
Light limitation and water velocity modify the impacts of simulated marine heatwaves on juvenile giant kelp.
Bunting I, Bornemann Santamaría L, Kok YY … +4 more , Krieger EC, Mullarney JC, D'Archino R, Cornwall CE
J Phycol · 2025 Oct · PMID 40678977 · Full text
Coastal regions are complex habitats, where multiple natural and anthropogenic drivers can interact to affect the survival and growth of marine organisms. The giant kelp Macrocystis pyrifera is sensitive to increasing se...
Coastal regions are complex habitats, where multiple natural and anthropogenic drivers can interact to affect the survival and growth of marine organisms. The giant kelp Macrocystis pyrifera is sensitive to increasing seawater temperatures and susceptible to marine heatwaves. Light availability and hydrodynamics can also affect the growth, morphology, and resilience of this species. In this experiment, juvenile sporophytes of M. pyrifera from Scorching Bay, Wellington, Aotearoa, New Zealand, a were exposed to a combination of simulated marine heatwaves at one of four different temperatures (20, 22, and 24°C compared to a 16°C control), one of two irradiance levels (shaded: 0.9 mol photons · m · d or ambient: 1.4 mol photons · m · d), and one of two flow speeds (5.3 cm · s or 6.1 cm · s) in a fully factorial design. Simulated heatwaves lasted for 21 days, with temperatures ramped by 2°C · d, followed by a 21-day recovery phase. The heatwave treatments represented severe heatwaves in present day or hypothetical future conditions, whereas the control represented historical average summer sea temperatures in Wellington, and 21 days represented a realistic duration for heatwaves in this region. Temperature was the main driver of negative physiological impacts, with 100% of sporophytes dying within 42 days of exposure to a 24°C heatwave. Sporophytes experienced 44% mortality at 20°C and 81% mortality at 22°C, and growth rates declined significantly with increasing temperature. However, survival rates were modified by light and water velocity, with 56% of sporophytes surviving under a combination of ambient light and fast water velocity, compared with less than 50% under each of the other light-velocity combinations. Light limitation also reduced sporophyte survival, growth rates, and effective quantum yield. Water velocity alone did not significantly affect sporophytes, but flow speeds had interactive effects with temperature and light. The findings of this experiment suggest that M. pyrifera at sites with optimal environmental conditions, including low sediment loads and fast tidal flows, could be more resilient to marine heatwaves, as long as temperatures do not exceed critical thresholds for survival.
Kalymmatonema gen. nov. (Scytonemataceae, Cyanobacteria): A desert soil crust genus previously identified as Scytonema hyalinum, with description of seven species new to science.
Bohunická M, Johansen JR, Pietrasiak N … +3 more , Jusko BM, Mesfin M, Becerra-Absalón I
J Phycol · 2025 Oct · PMID 40673602 · Full text
Numerous cyanobacterial strains previously identified as Scytonema hyalinum were determined to be phylogenetically distant from the type species of Scytonema, S. hofmannii. Morphological and molecular evidence suggests t...
Numerous cyanobacterial strains previously identified as Scytonema hyalinum were determined to be phylogenetically distant from the type species of Scytonema, S. hofmannii. Morphological and molecular evidence suggests this distinct clade necessitates placement in a new genus, and we have described Kalymmatonema gen. nov. herein. Kalymmatonema has been demonstrated to exhibit five ribosomal operons, all of which differed in both sequence and secondary structure of conserved helical domains in the 16S-23S internal transcribed spacer rRNA region. Four of these operon copies were highly similar in 16S and 23S rRNA gene sequences, whereas the divergent fifth copy is thought to represent a whole-operon horizontal gene transfer event. Through in-depth analysis, we were able to recognize seven species new to science, the type species K. desertorum sp. nov., K. arcangelii comb. nov., K. chimaera sp. nov., K. ethiopiense sp. nov., K. gypsitolerans sp. nov., K. mateoae sp. nov., and K. oahuense sp. nov. We also created the new combination, K. hyalinum comb. nov., in order to include the original Scytonema hyalinum in this new genus based upon the common morphological feature of a mucilaginous apical cap on the trichomes. Kalymmatonema displays a complex evolution of its ribosomal operons, with evidence not only of horizontal gene transfer but also of internal rearrangements and mobile genetic elements that have transposed the tRNA-containing region of the ITS rRNA region among the four similar operons. Additional investigation of the evolutionary history of this interesting genus will likely lead to a better understanding of the processes shaping ribosomal evolution in cyanobacteria.
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