Journal of Phycology最新文献

The Indian subcontinent has emerged as a natural habitat to several cyanobacterial taxa which have been explored and described in the past few years using a polyphasic approach. Various new genera and species of Nostoc morphotypes, heteropolar unbranched as well as branched heterocytous cyanobacteria, have been described from various parts of India such as the central mainland, temperate hill stations of extreme northern India, and the biodiversity hotspots of northeast India. Konkan, a small strip of land bounded by Arabian sea on the west and Sahyadri mountains on the east, has various habitats such as coastal beds, old monuments, freshwater lakes, and rivers; however, this region has been less charted in modern cyanobacterial systematics, relative to others. The region has a tropical climate with heavy monsoon showers owing to its location on the windward side of the northern Western Ghats, a global biodiversity hotspot. Through this study, several districts of the Konkan region of Maharashtra and Goa were explored for cyanobacterial diversity and evaluated through a polyphasic approach with three novel species of the genus Desikacharya, two novel species of the genus Pseudoaliinostoc and one new species of the monotypic genus Chlorogloeopsis being described in accordance with the International Code of Nomenclature for algae, fungi and plants (ICN).

Phytoplankton plays a crucial role in the fate of pollutants in aquatic ecosystems by biotransformation and bioaccumulation. Aniline was listed in priority pollutants due to its toxicity and widespread distribution in the aquatic environment. This study focused on investigating the capacity and mechanism of eukaryotic alga Chlamydomonas reinhardtii in transforming aniline. Results showed that the total removal percentage of aniline was 56% within 8 days at an initial concentration of 10 mg · L^-1. The percentage of the biotransformation by C. reinhardtii was 23.4%. The biotransformation product was identified as acetanilide, indicating that acetylation was the primary biotransformation pathway. To reveal the key enzyme of the biotransformation process, the N-acetyltransferase (NAT) gene was cloned from the C. reinhardtii genome, and the NAT protein was obtained through heterologous expression. Aniline was significantly transformed by the purified NAT protein in vitro, and the product was also acetanilide. The characteristics of C. reinhardtii NAT in biotransformation of aniline was analyzed by bioinformatics methods. The binding sites in C. reinhardtii NAT for ligands (aniline and acetyl-CoA) were identified. Three highly reserved valine residues (Glu⁸⁵-Asp⁸⁶-Val⁸⁷-Val⁸⁸-Val⁸⁹) as well as GLU¹³¹ and Cys¹²² were the indispensable amino acid residues for the catalysis from aniline to acetanilide. These results demonstrated the capacity of C. reinhardtii in the biotransformation of aniline, and the transformation process was primarily through N-acetylation of aniline to acetanilide catalyzed by NAT enzyme. This study provides novel insights into the biotransformation mechanism of aniline in eukaryotic green alga C. reinhardtii, facilitating the evaluation of the fate of aniline within aquatic ecosystems.

Kelp forests are among the most abundant and productive marine ecosystems but are under threat from climate change and other anthropogenic stressors. Although knowledge is growing about how the abundance and distribution of kelp forests are changing, much less is known about the "non-lethal" effects that global change is having on the performance and health of kelp populations in areas where they persist. Here we assessed the age distribution of two common stipitate kelp species, Laminaria setchelli and Pterygophora californica, at Wizard Islet in Barkley Sound, British Columbia, Canada, and compared these data to historical demographic data collected by De Wreede (1984) and Klinger and DeWreede (1988) from the same site between 1981 and 1983. We observed that L. setchelli populations in 2020 were younger and less evenly aged than the same populations sampled nearly four decades prior, while the P. californica population was composed of older individuals on average than at the historical time point. Although the drivers of these demographic changes remain unclear, Barkley Sound has experienced substantial changes in the physical and biological environment over the past decade that could be responsible for these patterns. Given that the size of an individual and its probability of reproduction increases with age, shifting demographics may impact the reproductive output of each population, potentially altering the competitive relationships between co-occurring species. Changes in size distribution may also influence ecosystem-level processes such as habitat complexity or productivity.

The filamentous red algal genus Bryocladia was recently deeply revised based on molecular and morphological data. However, data from the Southwestern Atlantic Ocean are scarce. Here, we provide a phylogenetic study of Bryocladia representatives from the Brazilian coast with new additions to the genus. Our samples were collected from the north to southeastern Brazilian coast in marine and estuarine areas. We carried out a morphological and molecular study based on COI-5P and rbcL gene sequences. Our phylogenetic analyses confirmed the presence of seven species on the Brazilian coast, four of which were previously known: B. cuspidata, B. subtilissima, B. thyrsigera, and B. villum. Three new species are described here, B. itaipensis sp. nov., B. oceanica sp. nov., and B. mucuripensis sp. nov., all morphologically included in the B. scopulorum complex. Bryocladia subtilissima was observed only in Brazilian estuarine areas. However, it was split into two subclades, which require further investigation. The three new species expand the known diversity of the B. scopulorum complex from 12 to 15 species. Bryocladia itaipensis is closely related to B. canariensis and B. caespitosa, whereas B. oceanica and B. mucuripensis formed distinct lineages with unsolved relationships. All new species are restricted to their type localities in Brazilian waters, reinforcing the need for further study of tiny species, especially from the tribes Polysiphonieae and Streblocladieae.

Sea ice can profoundly influence photosynthetic organisms by altering subsurface irradiance, but it is susceptible to changes in the climate. The patterns and timing of sea ice cover can vary on a monthly to annual timescale in small sub-regions of the Western Antarctic Peninsula (WAP). During the latter part of the 20th century, sea ice coverage significantly decreased in the WAP, a trend that aligns with warming in this area. Macroalgal biochemical components are impacted by light availability, often showing a close relationship between photosynthesis and biochemical compositions. We used satellite imagery of annual sea ice duration and extent as well as water turbidity during ice-free periods to identify 14 study sites that differed dramatically in sea ice coverage but were similar in terms of turbidity along the central WAP between 68° S and 64° S. The common macroalgal species Desmarestia menziesii, Himantothallus grandifolius, Sarcopeltis antarctica, and Iridaea sp. were collected by scuba divers between 5 m and 35 m depth at each site where they occurred, for later biochemical analyses. Overall percentages of major biochemical components as well as carbon and nitrogen percentages and C:N were determined and correlated with four different sea ice indices. Surprisingly, most of the chemical components were not significantly correlated with sea ice cover. The few significant correlations varied between species and chemical components. This indicates that although patterns of sea ice coverage have major implications for macroalgal abundance, on a per-biomass basis, sea ice coverage does not impact the nutritional contributions of macroalgae to food webs.

Delta-6 fatty acid desaturases, which play key roles in the biosynthesis of polyunsaturated fatty acids (PUFAs), are membrane-associated enzymes that present significant challenges for isolation and purification, complicating their structural characterization. Here we report the identification and structure-function analysis of a novel Δ6 fatty acid desaturase (PmD6) from the marine alga Prorocentrum micans with substrate preference to α-linolenic acid (18:3n-3). Structural modeling revealed a mushroom-like structure of PmD6 formed by four transmembrane α-helices as a stem and three cytoplasmic domains as a cap. Structural alignment identified several key residues positioned around the substrate tunnel and catalytic center in PmD6. Functional analysis of these residues by site-directed mutagenesis showed that Tyr226, Trp235, Phe345, and Ser349, facing the middle region of the substrate tunnel of PmD6, played critical roles in defining the structure for acceptance of substrates. Thr200, Leu391, and Met389, surrounding the end of the substrate tunnel, had roles in interaction with the methyl end of substrates. Asp255, close to a metal iron in the catalytic center, was essential for catalytic reaction by supporting the regional structure. These results have provided mechanistic insights into the structure-function relationship of membrane-bound front-end fatty acid desaturases.

Over 400 cyanobacterial genera have been described up to the present. Since the Cambridge Rules (https://www.iapt-taxon.org/historic/1935.htm: Rendle 1935), a type species (generitype) must be specified at the time of description for a new genus to be validly described. Even though we have entered a time in which sequencing has become practical and widespread, the basic molecular characterization (e.g., 16S rRNA gene sequence) of most cyanobacterial generitypes is still lacking. About 15 cyanobacterial genera were originally described from Scandinavia. Following a field excursion in which the type or syntype localities for the type species of these genera were visited and sampled, we succeeded in finding three type species from their type or syntype localities: Capsosira brebissonii, Stigonema mamillosum, and Paracapsa siderophila. Epitypes for all three generitypes are herein established. Cells or filaments of C. brebissonii and S. mamillosum were isolated and used for single-cell/filament PCR amplification of the 16S rRNA gene and subsequent cloning and sequencing of the PCR amplicons. This allows a firm establishment of reference sequences of these two genera, to which morphologically similar taxa can now be compared. Stigonema and Capsosira are shown herein to be sister to Aetokthonos hydrillicola, a cyanobacterium known to cause avian vacuolar myelinopathy in birds, including bald eagles.

Cyanobacteria exhibit a vast diversity from polar to tropical environments. Though much work has been done on elucidating their biodiversity, knowledge on the occurrence, diversity and toxicity of benthic cyanobacteria is limited when compared to the planktonic forms. Integrating molecular techniques with ecological and morphological analyses has become essential in untangling cyanobacterial diversity, particularly for benthic taxa such as the cryptic "Lyngbya." Molecular markers such as the 16S rRNA gene and whole genome sequencing have significantly improved the taxonomy of cyanobacteria. Building on these advancements, this study characterizes benthic cyanobacterial isolates from various locations in Florida, USA, and Orange Walk, Belize, resulting in the identification of a novel genus, Floridanema, and four new species (F. aerugineum, F. evergladense, F. flaviceps, and F. fluviatile). This new genus commonly occurs in canals, ponds, lakes and rivers. By integrating ecological, morphological, and genomic analyses, this study provides support for the family Aerosakkonemataceae and the establishment of the order Aerosakkonematales. The LC-MS data revealed that Floridanema strains do not produce microcystins, nodularin-R, or anabaenopeptins.

The composition and abundance of crustose coralline algae (CCA) have been documented in the Xinfeng algal reef (XAR). Eight CCA species were identified, including four in Phymatolithon (P. margoundulatum, P. taiwanense, P. variabile, and Phymatolithon sp.) and four only identified to the genus level (Chamberlainium sp. and three Dawsoniolithon spp.). Chamberlainium sp. was the most abundant species, while the three species of Dawsoniolithon were rarely observed. The CCA coverage varied from 18% ± 15% to 27% ± 21% in spring seasons of 2021-2024, but there were no significant differences. Based on carbon-14 dating, the CCA sediments in the XAR were estimated to be 5850-5990 years old. These CCA sediments were primarily composed of two paleo-CCA species, resembling modern Chamberlainium sp. and Dawsoniolithon sp. 1. However, the modern species of Phymatolithon, which are widespread and abundant in the algal reefs of northwestern Taiwan, were not observed in the CCA sediments. It is unclear whether their absence was due to fragile thalli after their death or their lack of occurrence, and this requires further investigation. The paleoenvironmental data and biogenic sediment composition analysis suggests that the XAR started to develop ~6000 years ago when the sea surface temperature began to decrease and seawater turbidity increased due to rainfall. Additional CCA sediment samples from this algal reef are needed to fully understand the historical changes in the paleo-environments in the XAR.

Chlorophyll (Chl) f was reported as the fifth Chl in oxygenic photoautotrophs. Chlorophyll f production expanded the utilization of photosynthetically active radiation into the far-red light (FR) region in some cyanobacterial genera. In this study, 11 filamentous cyanobacterial strains were isolated from FR-enriched habitats, including hydrophyte, moss, shady stone, shallow ditch, and microbial mat across Central and Southern China. Polyphasic analysis classified them into the same genus of Leptodesmis and further recognized them as four new species, including Leptodesmis atroviridis sp. nov., Leptodesmis fuscus sp. nov., Leptodesmis olivacea sp. nov., and Leptodesmis undulata sp. nov. These cyanobacteria had absorption peaks beyond 700 nm due to Chl f production and red-shifted phycobiliprotein complexes under FR conditions. All but L. undulata produced phycoerythrin and showed varying degrees of a reddish-brown to dark green color under white light conditions. However, the phycoerythrin contents were sharply decreased under FR conditions, and these three Leptodesmis species appeared green. In summary, the Leptodesmis genus contains diverse species with the capacity to synthesize Chl f and is likely a ubiquitous group of Chl f-producing cyanobacteria.