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We present a synopsis of studies reporting the free-living occurrence of green algal lichen symbionts. We give an overview of all known lichen photobiont genera together with comprehensive descriptions, taxonomical classification and occurrence data. Based on the analysis of 310 records, we discovered that at least 80% of lichen photobiont genera were observed in the free-living state. Diplosphaera chodatii, Elliptochloris bilobata and Chloroidium ellipsoideum represent both morphologically and genetically the most frequently reported free-living photobiont species. Trebouxia, the most prevalent genus of lichen photobionts, has frequently been reported to exist independently to fungal hyphae. Based on our literature survey, free-living photobionts of lichens are able to grow in a wide range of environments and substrates, with most records coming from soil and biological soil crusts. [ABSTRACT FROM AUTHOR]

The modern concept of the genus Chloromonas includes a subclade of species found exclusively in snow. We describe Chloromonas (Cr.) fuhrii sp. nov., a new member of this clade, which is closely related to Cr. muramotoi from Japan. The new species is characterised by the absence of a stigma, pyrenoid, and defined papilla, ready loss of flagella in culture, and a single lobed chloroplast. Strains of Cr. fuhrii have been sourced from green, orange, and pink/red snow. The species has been found in Svalbard, Antarctica, and New Zealand, with most genetic variation occurring in Svalbard. The minimal variation present in New Zealand strains suggests a relatively recent arrival. Secondary structure models for ITS2 in the new species demonstrate a separation from Cr. muramotoi due to one CBC. The nine New Zealand strains isolated showed no variation in ITS2 but four variable base positions in ITS1. Inclusion of the single Antarctic and four Svalbard strains resulted in 14 variable positions in ITS2 and 69 in ITS1, with the sequences remaining alignable. The ITS data showed a strong biogeographic signal, both in total in an unrooted tree, and using ITS2 alone with Cr. muramotoi as an outgroup. The absence of a stigma in this species prompted a survey of the literature, showing that stigma absence in Chloromonas is strongly associated with the snow habitat, occurring at about 10 times the rate observed in other habitats, perhaps owing to the difficulty of phototaxis in snow with abundant reflected light. [ABSTRACT FROM AUTHOR]

An undescribed variety of the green alga Chlorella cf. vulgaris was found living in the octocoral (soft coral) Sarcophyton sp., which also has dinoflagellate zooxanthellae. The green alga is present in very small numbers and is capable of photoheterotrophy based on growth in the presence of an inhibitor of photosynthesis, DCMU, with glycerol provided as a carbon source. The presence of zoochlorellae (Chl a + b), in soft corals appears to have been unsuspected. The easily cultured green alga was unicellular, unflagellated and very small, c. 2 to 6 µm in diameter and had a relatively high Chl b content (Chl b/a = 0.379 ± 0.063). Rapid light curves using PAM fluorometry on the cultured cells showed that Yield vs. irradiance had a low maximum yield (Ymax, 0.388 ± 0.0132; Irradiance ½ point, E½Ymax = 139 ± 11.1 µmol photon m–2 s–1). The overall optimum irradiance (Eopt) for the alga was 314 ± 18.8 µmol photon m–2 s–1. The alga can photosynthesize at 50% or more of the optimum rate from 70 to 900 µmol photon m–2 s–1 but would be severely inhibited under full sunlight. Most naturally occurring low irradiance habitats may have a low median irradiance but are exposed intermittently to very high irradiances and so a relatively high Eopt is advantageous in minimizing photochemical damage. Like the green algal symbiont Elliptochloris marina of sea anemones, Chlorella cf. vulgaris is not exclusively marine: it grows better in freshwater medium where it has different photosynthetic characteristics (higher Ymax, Eopt and ETRmax). Chlorella cf. vulgaris appears to be capable of photoheterotrophy and it is not clear if it is a symbiont, a commensal or a parasite. [ABSTRACT FROM AUTHOR]

Three series of experimental treatments were carried out to assess five indigenous green algae for biomass quality, productivity, and phycoremediation potential under varying N, P, NP, and N:P in Bold's Basal Medium. Algae showed species-specific responses to particular concentrations of N, P, NP, and N:P ratio in the medium. Most species showed their highest yield and productivity in N-varied treatments (2–3 × N with N:P = 3.42–5.13), whereas the lowest yield occurred in P-varied treatments (3–4 × P with N:P = 0.68–0.53). A low N:P from a decrease in N was favourable to Chlamydopodium starrii, whereas a low N:P from an increase of P was favourable to Chlorococcum humicola. A high N:P from an increase of N was favourable to Scenedesmus javanensis. An increase of N:P by adding more N increased the nitrogen removal rate (NRR) of C. humicola and S. javanensis. However, S. javanensis showed the highest phosphorus removal rate (PRR) at low N:P (0.68) from 3 × P in the medium. Algal protein content was directly proportional to the amount of nitrogen in all species except S. javanensis. Chlamydopodium starrii showed the highest protein content at 4 × N in the medium. N starvation stimulated an increase of lipid content in all five microalgae, and the lipid content of C. starrii and Parachlorella kessleri was significantly higher than that of others. Overall, the experiment constitutes a model to identify the optimum nutrient requirements for maximum phycoremediation potential and quality biomass productivity of particular algal species. [ABSTRACT FROM AUTHOR]

Understanding the related mechanisms between aerobic respiration and lipid biosynthesis may promote microalgal-biofuel industries through metabolic engineering. However, little is known about how aerobic respiration affects lipid biosynthesis in microalgae. Here, the changes in biochemistry and molecular biology were analysed in Auxenochlorella pyrenoidosa throughout nitrogen limitation (–N) and nitrogen resupply (+N) phases. Respiratory inhibitors were used to identify the roles of respiratory complexes in lipid biosynthesis. We found that during –N phase the growth profiles, and the amount and productivity of chlorophyll a, carbohydrates and proteins decreased, while the content and productivity of lipids increased. In addition, the lower unsaturation (DU ≤ 96.41 ± 0.38) showed that lipid accumulation under nitrogen limitation in A. pyrenoidosa was qualified for biodiesel production. Either relationships or significant correlations were found between lipid contents, reactive oxygen species (ROS), respiration rates, respiratory complexes activities and key gene expression in treatment groups. Moreover, the trends in the activities of complexes I and III, lipid contents and ROS production in +N phase were different from those in –N phase. Finally, the respiratory inhibitors increased the levels of total ROS and lipids in A. pyrenoidosa. These results suggested that nitrogen limitation may inhibit redox centers of complexes I and III in respiratory chains through mitochondria and nucleus, thus regulating intracellular ROS and lipid accumulation. [ABSTRACT FROM AUTHOR]

The green algal genus Ulva is one of the most widely distributed macroalgal genera. The taxonomy of Ulva is problematic due to its simple morphology. The study of the diversity of this genus has undergone great advances using molecular data, leading to changes in the taxonomic status of species, and the recognition of species complexes and cryptic species. Here we reassessed Ulva species from southeastern Brazil using molecular data. We recognized 10 taxa, among which only three previously reported species were confirmed by molecular data: U. compressa, U. lactuca and U. ohnoi, the latter recently recorded from insular waters in Fernando de Noronha Archipelago, northeastern Brazil. Our phylogenetic analyses and species delimitation methods strongly supported the establishment of Ulva kanagawae sp. nov. The species traditionally cited for southeastern Brazil, U. flexuosa, U. linza, U. rigida and U. paradoxa, proved to be misapplied names of U. tepida, U. aragoënsis, U. ohnoi/U. lactuca and U. torta, respectively. One taxon, Ulva sp., remains unnamed and needs further studies. Ulva chaugulei and U. tanneri, both considered here as cryptogenic species, are new occurrences for Brazil expanding their geographic distribution to the Atlantic Ocean and western Atlantic Ocean, respectively. In addition, our analysis of sequences from type materials revealed that U. pseudo-ohnoi is a heterotypic synonym of U. conglobata. This first systematic molecular study of Ulva species in Brazil points out that more extensive sampling is needed to reveal the true diversity of the genus in Brazilian waters. [ABSTRACT FROM AUTHOR]

Oxidative stress damages cellular components and may lead to cell death when it is not effectively counterbalanced by the endogenous antioxidant mechanisms. Exogenous sources of antioxidants are also necessary to cope with high levels of free radicals. Microalgae are rich sources of diverse metabolites with high antioxidant potential. In this study, metabolites of Hindakia tetrachotoma ME03, a green microalga previously isolated from thermal springs in Türkiye, were chemically fractionated using four solvents (ethanol-water, ethyl acetate, hexane and water). The extracts were evaluated for their antioxidant capacities, total phenolics, flavonoids and carotenoids. The highest antioxidant capacity, phenolic and carotenoid contents were obtained in the ethanol-water extracts. The antioxidant capacity in the ethanol-water extracts was measured as 12.42 ± 1.21 μmol Trolox g–1 DW and 67.98 ± 3.45 μmol Trolox g–1 DW by DPPH and FRAP assays, respectively. Twelve different phenolic compounds in the ethanol-water and ethyl acetate extracts were quantified by reverse phase high pressure liquid chromatography. Quercetin and rutin were the most abundant phenolics in the ethanol-water extracts, whereas the ethyl acetate extract was rich in phenolic precursor, benzoic acid. Finally, the cytoprotective effect of ethanol-water extracts of H. tetrachotoma ME03 against H2O2-induced oxidative damage was investigated using an in vitro cell line model of human breast adenocarcinoma (MCF7). Hindakia tetrachotoma ME03 extracts significantly decreased the intracellular reactive oxygen species levels and the percentage of apoptotic and necrotic cells in MCF7 cells. These findings suggest the strong cytoprotective activity of H. tetrachotoma ME03 extracts, which may be conferred by its antioxidative properties. [ABSTRACT FROM AUTHOR]

The diversity of monosaccharides and glycosidic linkages of extracellular polysaccharide (EPS) of high molecular weight were studied in strains morphologically assigned to the genus Ankistrodesmus. EPSs of seven strains were similar in both monosaccharides and glycosidic linkages, but showed exclusive characteristics or enough differences in proportions to distinguish strains. Fucose, glucose, rhamnose, mannose and galactose occurred in relatively high percentages in all strains. The strain CCMA-UFSCar 423, excluded from the genus Ankistrodesmus by the molecular marker tufA, was the only one containing galacturonic acid. Arabinose was found only in one A. densus strain (CCMA-UFSCar 239). The species A. densus and A. stipitatus, which are known to have, respectively, stable mucilaginous capsules and pads in aqueous media, presented high percentages of the hydrophobic fucose and rhamnose on their polysaccharides. However, the strain CCMA-UFSCar 83, the only non-colonial A. densus, had low proportions of rhamnose. We also found variations in glycosidic linkages, and some of them were specific to one strain (e.g. 1-3 glucose in A. stipitatus). Conversely, the absence of common linkages was noteworthy for the strain outside the Ankistrodesmus clade, the CCMA-UFSCar 423. The data revealed important diversity in monosaccharides and linkages of the EPS within a single microalgae genus, and an important intraspecific diversity using a single growing condition. These differences could be useful as potential chemotaxonomic tools to help discriminating the Ankistrodesmus genus or species, but also for future studies on intraspecific diversity within the genus. Moreover, the results show the relevance of studying and conserving closely related strains to preserve biodiversity. The diverse composition of high molecular weight EPSs shows a great potential for prospecting EPSs of economic interest. [ABSTRACT FROM AUTHOR]

Underwater CO2 vents represent natural laboratories where the responses of marine organisms to ocean acidification can be tested. In a such context, we investigated the changes in the physiology, anatomy, and ultrastructure of the non-indigenous algal species Caulerpa cylindracea growing along a natural pH/CO2 gradient, by conducting a reciprocal transplant experiment between two populations from an acidified vs a non-acidified site. Stress effects in transplants from current to lowered pH conditions resulted in a decrease in the number of active chloroplasts together with an increased number of dilatations between thylakoid membranes and a higher amount of plastoglobules. These changes were consistent with a decrease in the chlorophyll content and in photosynthetic efficiency, matched by an increase in carotenoid content and non-photochemical yields. On the opposite side, transplants from low to current pH showed a recovery to original conditions. Unexpectedly, no significant difference was recorded between wild populations living at current and lowered pH. These results suggest an ongoing acclimation process to lowered pH in the C. cylindracea populations growing in the vent area. This confirms the high plasticity of this invasive species, able to cope not only with different light and temperature conditions but even with a new acidified scenario. [ABSTRACT FROM AUTHOR]

Microbial biofilms colonizing cultural heritage sites are detrimental due to the production of exudates which deteriorate archaeological surfaces. In this study, a number of microalgal strains isolated from biofilms in hypogea and catacombs were investigated using a multiphasic approach to describe their diversity. Microscopic observations and genetic analyses revealed that the minute coccoid cells belonged to the genus Jenufa. For the first time, ecophysiological characteristics of Jenufa spp strains have been studied and their intracellular, capsular and secreted metabolites quantified. Optimal growth was achieved in nutrient-rich conditions, in which the cells produced substantial amounts of cellular, capsular, colloidal and secreted metabolites. The capsule was composed of high amounts of protein. Under nutrient limitation, Jenufa spp cells produced high quantities of carbohydrates. Both Jenufa cells growing in situ on archaeological surfaces and those cultured in vitro were capable of sustained growth and active secretion of exopolymers for extended periods of time with minimal input of nutrients from outside sources. [ABSTRACT FROM AUTHOR]

A Sardinian small trebouxiophycean alga, Laetitia sardoa, is described as a novel species and genus. This green alga was collected in an oligotrophic freshwater habitat, and its morphology was investigated. The strain established belongs to the order Chlorellales, of the class Trebouxiophyceae, as inferred from phylogenetic analyses of nuclear-encoded 18S rDNA and chloroplast-encoded ribulose-bisphosphate carboxylase-oxydase gene (rbcL). The analyses supported Laetitia as a distinct lineage, sister to a Marvania clade. The taxonomy of this order has long been problematic due to the lack of distinguishable morphological characteristics. With the characterization of this microalgal strain, we confirmed the necessity of using molecular analyses to determine these cryptic algae. Moreover, our study contributes to the knowledge of the taxonomy and ecology of Chlorellales (Chlorophyta). In addition, the discovery of this new genus in the Ogliastra's Tacchi suggests the potential diversity of this area, which up to now has remained largely unknown, and increases the general knowledge of the microalgal flora of this region. [ABSTRACT FROM AUTHOR]

A phylogeographic approach is the only way to study the dispersal history of most algae, which are rarely preserved as fossils. However, the only freshwater alga for which this approach has been applied on a Eurasian scale is the endangered green alga Aegagropila linnaei, which is thought to be a poor disperser. Previous phylogeographic results were explained by stepwise dispersal across the Holarctic from an ancestral area in Japan, with further survival in European ice-dammed glacial lakes and extinction in continental Siberia, which lacks such refugia. To clarify the biogeography of A. linnaei in Eurasia we supplemented the published data on its ribotype (internal transcribed spacer of ribosomal DNA) distribution with data from previously unexplored East Europe, Mongolia and the Russian Far East. We have found two new ribotypes, one scattered across temperate Europe and another confined to one locality in the north-eastern Russian Far East. We also expanded the distribution of a ribotype previously reported from Scotland and continental West Europe to include East Europe, Iceland and Central Mongolia. Phylogeogeographic approach based on enhanced sampling allowed us to refine the biogeography of A. linnaei. We discuss reasons for underestimation of A. linnaei dispersal potential. A focused inventory of A. linnaei will likely reveal new localities of the species enabling a further improvement in biogeographical reconstructions. Area-wide studies of other freshwater algae in Eurasia need to be performed to test the generality of the revealed biogeographical patterns. [ABSTRACT FROM AUTHOR]

Zygnematophyceae are main primary producers in polar hydro-terrestrial habitats, characterized by extreme abiotic conditions. They are expected to be strongly impacted by climate change, leading to threats to subpolar and polar ecosystems. Two isolates of Zygnema from a subpolar (Iceland, Zygnema sp. I) and a polar Island (Svalbard, Zygnema sp. B) were compared by their photophysiological performance and phenolic content. A phylogenetic analysis was performed in a newly isolated Zygnema I where also morphology and ultrastructure were characterized. The rbcL sequence of the Icelandic Zygnema I was identical to that of Zygnema V, previously isolated from Svalbard, and phylogenetic analysis placed this strain into Zygnema clade 2. Average width of vegetative filaments (28 ± 0.7 µm) and ultrastructure was similar to closely related Zygnema strains. Zygnema I and Zygnema B were exposed to three different treatment temperatures (15, 20 and 25°C) for two weeks, then photophysiological parameters and cellular phenol contents were acquired. The maximum electron transport rate increased significantly with elevated temperatures, but non-photochemical quenching did not change. Net photosynthetic oxygen production was higher in Zygnema B, but decreased in both strains from 10 to 15°C measuring temperature. Zygnema I showed a significant decrease between 15/25°C-treated cultures above 20°C measuring temperature. The phenolic content did not change significantly with experimental treatments, the spectral absorption at 350 nm was significantly lower in Zygnema B when compared with Zygnema I. Taken together our results indicate that Zygnema B and Zygnema I cannot adapt to elevated temperatures. [ABSTRACT FROM AUTHOR]

Three strains of a coccoid green alga were isolated from soil samples collected at the Shiveluch Volcano on the Kamchatka Peninsula. SSU rRNA gene sequence comparisons resolved the strains as members of the genus Eremochloris in the class Trebouxiophyceae. Analyses based on the internal transcribed spacer (ITS) rRNA secondary structure revealed that our isolates were genetically distinct from the type species of this genus. These isolates were characterized by spherical, elliptical or pyriform cells that were solitary with a single excentric nucleus. The cells harboured a single-pyrenoid parietal chloroplast, which was either simple or dissected into clear, curved or undulated lobes. Studies on the life cycle of this alga revealed that asexual reproduction takes place via autospores or biflagellated zoospores. Sexual reproduction is very scarce and is isogamous. All these features suggest a new species, which we name Eremochloris kamchatica. The description of the genus Eremochloris is emended to accommodate the features of the new species. [ABSTRACT FROM AUTHOR]

Identification of planktonic flagellates is challenging, and multiple species are often lumped together, limiting our understanding of their diversity and ecology. Our aim was to investigate changes in the phytoplankton community composition over the annual cycle in Roskilde Fjord, Denmark, focusing on the identification of organisms smaller than 20 µm. Weekly microscope and pigment data indicated a low contribution of diatoms and dinoflagellates and the importance of cryptophytes, euglenophytes and green algae, with high contributions of alloxanthin and chlorophyll b. Community composition using Serial Dilution Cultures (SDC) confirmed the high contribution of cryptophytes, prasinophytes and euglenophytes in the phytoplankton community. In contrast, diatoms only played a minor role. Seasonal changes were observed within cryptophytes, with Teleaulax dominance during cold months shifting to Hemiselmis in summer. Small prasinophytes and pico-eukaryotes were always present but had a low relative contribution to the total phytoplankton biomass. Cultured organisms enabled the identification of Hemiselmis cf. cryptochromatica, recorded for the first time in European waters, and an undescribed Pyramimonas species. We describe the new species as Pyramimonas octopora sp. nov., placed within Pyramimonas subg. Vestigiferae, based on morphological and molecular (SSU rDNA) data. The distinctive features of the new species are the eight irregularly rounded perforations arranged in a square box with rounded corners around the centre of the base plate of the box scales, and the complex crown scales, not observed in previously described Pyramimonas species. [ABSTRACT FROM AUTHOR]

The potentially biodeteriogenic, subaerial green alga Trentepohlia umbrina is widely distributed on shaded substrates with northern aspects. This preference for low light was confirmed by a recent survey in Lazio, Italy. However, the same survey revealed an isolated occurrence of extensive growths of T. umbrina-dominated biofilms on surfaces with diverse aspects that ranged from highly exposed to shaded. Prior studies of Trentepohlia photosynthesis have been restricted to single sites, so this multi-aspect site was particularly interesting to understand the photoacclimation potential of Trentepohlia. Photosynthetic pigment concentrations and chlorophyll fluorescence (in situ and ex situ) were used to assess the photosynthetic response to changes in light exposure and humidity. Pigment contents and photoinhibition decreased, while the maximum photosynthetic rate and the level of light that saturated photosynthesis increased with an increasing light exposure duration (ranging from c. 5 to 300 min d–1 of exposure to sunlight). Laboratory tests of relative humidity (RH) on biofilm photosynthesis showed no recorded activity up to 32% RH, only 26% of the maximum activity at 77% RH, and full activity at 92% RH. When T. umbrina was in the desiccated state a lowering of basal of chlorophyll a fluorescence emission and a loss of variable fluorescence occurred. This suppression of fluorescence when cells are desiccated is known to result in photoprotection of reaction centres from continuing high irradiances, as the enhanced thermal dissipation replaces slower and potentially damaging energy transfer to the functional reaction centres. It was concluded that T. umbrina has a much wider environmental range than previously thought, but its growth is very slow and may be overlooked during cultural heritage surveillance, leading to inconspicuous chronic degradation of outdoor stone substrata. [ABSTRACT FROM AUTHOR]

The green alga Chlorella sp. and the filamentous cyanobacterium Leptolyngbya sp., regularly cope with various stressors including frequent hydration–desiccation cycles. When grown in axenic cultures, Chlorella sp. is unable to resurrect even after very slow desiccation unless desiccation takes place in the presence of Leptolyngbya sp. or a lysate thereof. When Chlorella sp. was provided with extracellular polysaccharides from Leptolyngbya sp., or its main sugar constituents, it was able to be resurrected after mild desiccation. These findings suggest that desiccation tolerance of Chlorella sp. in the field depends on the presence of Leptolyngbya sp. or components thereof. Chlorella sp. was originally isolated as a contaminant in a decaying stationary culture of Leptolyngbya sp. that was established by the addition of a cyanobacterial growth media to biological soil crusts. Co-incubation with a dialysis tube containing Leptolyngbya sp. severely inhibited growth of Chlorella sp. These data suggest that secondary metabolites excreted by Leptolyngbya sp., the nature of which is yet unknown, inhibit growth of Chlorella sp. Thus, though Leptolyngbya sp. enables the survival of Chlorella sp. in a desert habitat, it simultaneously inhibits growth of this potential competitor. The combination of positive and negative effects of Leptolyngbya sp. on fitness of Chlorella sp. creates a scenario in which the former tightly controls the abundance of the latter. [ABSTRACT FROM AUTHOR]

Copper is a micronutrient essential for the growth of photosynthetic organisms. However, it is highly toxic at supraoptimal concentrations, causing oxidative stress. Living organisms defend themselves against reactive oxygen species (ROS) via the synthesis of ROS-detoxifying enzymes and low-molecular-weight antioxidants. In the present paper, the antioxidant response of model green microalga Chlamydomonas reinhardtii exposed to 20 and 25 µM CuSO4 was monitored during various stages of growth (exponential growth phase, stationary phase, decline phase). The aim of the study was to measure the effect of Cu on algal growth along with antioxidant responses. The content of both hydrophilic (ascorbate and its oxidized form dehydroascorbate, total thiols, proline) and hydrophobic (tocopherols, plastoquinol, plastochromanol) low-molecular-weight antioxidants, as well as the activity of superoxide dismutase, catalase and ascorbate peroxidase were measured. After seven days of growth, a significant decrease in cell number and chlorophyll content was observed in Cu-treated culture batches. This was accompanied with the increase in total ascorbate content and antioxidant enzyme activity, whereas the levels of major prenyllipid antioxidants decreased. The differences in cell number and chlorophyll content were less pronounced at later growth stages. There were also no pronounced increases in ascorbate and antioxidant enzyme activities. It was concluded that the enhanced oxidative stress occurred at the earlier stages of growth. This conclusion is supported by the results of the assessment of lipid peroxidation markers. [ABSTRACT FROM AUTHOR]

There has been disagreement on the ubiquity, or even the presence, of free-living populations of photobionts that are lichen-associated. This review summaries the finding of studies showing that free-living populations of green algae often found in lichens, especially in the class Terbouxiophyxeae, are common. The capture of these algae by fungi may be more a case of enslavement over mutual benefit (see Veselá et al. 2024, this issue).Graph [Extracted from the article]

Cephaleuros is a subaerial green alga widely distributed in tropical and subtropical regions. In this study, we investigated the taxonomy of Cephaleuros in southern China. Eight morphospecies (C. virescens, C. karstenii, C. expansus, C. drouetii, C. diffusus, C. tumidae-setae, C. lagerheimii and C. parasiticus) were identified according to previous descriptions, among which C. karstenii was the most frequently recorded. Subsequently, molecular phylogeny of Cephaleuros was inferred from 18S rDNA, ITS rDNA, 28S rDNA and rbcL sequences. Cephaleuros was subdivided into nine clades based on ITS analysis, which were recovered in phylogenies of two concatenated datasets (18S+ITS+28S and 18S+ITS+28S+rbcL). Molecular analyses revealed that Cephaleuros was composed of two main lineages, with one lineage comprising mostly samples of C. karstenii and C. virescens and the other comprising other species. The molecular phylogenies were not congruent with conventional morphological classifications, although some clades were distinguished by one or more diagnostic features. While the morphological features used to distinguish Cephaleuros spp were not reliable, the rbcL gene proved to be a good marker for identification of Cephaleuros. The ITS2 secondary structure prediction model showed that Cephaleuros spp have one ring structure with four helices, with Helix III being the longest without a branch in clades 3, 5 and 8. The present study represents the most detailed taxonomic assessment of Cephaleuros available to date. Further taxonomic research incorporating samples from the type locality is necessary for the reassessment of C. virescens. [ABSTRACT FROM AUTHOR]

The phylogroup Chloromonadinia (Volvocales, Chlorophyceae) comprises green microalgae that inhabit a variety of environments, including freshwater, soil, and snow. Two strains were isolated from two sites in the South Shetland Islands in maritime Antarctica, and their morphological and molecular characteristics were studied. Light microscopy of the strain KSF0090 revealed ellipsoidal or broad ellipsoidal, sometimes almost spherical cells with a chloroplast without a pyrenoid, a prominent eyespot, and a hemispherical papilla. The vegetative cells of KSF0208 were ellipsoidal to ovoid cells with a chloroplast with a central pyrenoid, a linear eyespot, and a papilla. The two strains differed from other closely related species based on size and the aforementioned morphological characteristics. Nuclear small subunit rDNA sequence data indicated that each strain formed a distinct well-supported lineage within the phylogroup Chloromonadinia. In addition, comparative analyses of the secondary structures of internal transcribed spacer 2 and compensatory base changes were used to identify and characterize the two strains. Based on their morphological and molecular characteristics, we propose KSF0090 and KSF0208 as two new species, Chloromonas deceptionensis sp. nov. and Ostravamonas greenwichensis sp. nov., respectively. [ABSTRACT FROM AUTHOR]

Cladophora is one of the most species-rich and taxonomically challenging taxa of green algae. Recently, some samples of freshwater filamentous algae were collected from Hubei, Yunnan and Guizhou Provinces, China. The specimens grew attached to solid substrates by basal rhizoids or holdfasts, and their thalli were bright to dark green, long and stiff. They were typically composed of uniseriate unbranched filaments of approximately equal length produced by intercalary and apical cell divisions. We studied the taxonomy of these algae based on morphological and molecular data. Microscopic observations showed that the filaments had some characteristics that differed from those of other species of Cladophora, such as being unbranched, with a large cell diameter (180–429 µm) and smaller length:diameter (L:D) ratio (0.5–3.3) than other species. Phylogenetic trees constructed on the basis of small (SSU) and large (LSU) subunits of ribosomal DNA (rDNA) and the internal transcribed spacer (ITS) sequences showed that all collected specimens belonged to one species. These specimens formed a new clade in the freshwater Cladophora lineage. On the basis of the morphological and phylogenetic analyses, we propose a new species, Cladophora rigida sp. nov. [ABSTRACT FROM AUTHOR]

Routine DNA barcoding with the chloroplast gene tufA identified novel records of an unknown and denuded (i.e. lacking branchlets) Caulerpa species previously reported from the Florida Middle Grounds. tufA barcoding not only confirmed the matching molecular identity of this taxon with several newly collected denuded specimens from shallow habitats of the Yucatán shelf, but also with a set of plumose specimens previously collected from mesophotic depths of the West Florida shelf and recorded as Caulerpa sertularioides. Sequencing of two additional, faster-evolving DNA markers, i.e. nuclear ITS and the newly tested chloroplast-encoded rpoA, each confirmed conspecificity of the above morphotypes and the molecular separation of the new taxon from C. sertularioides and filiform species found in the region, namely C. cupressoides f. denudata and C. fastigiata. In light of our sequencing results and review of the early taxonomic history of filiform Caulerpa, we propose the description of Caulerpa wysorii sp. nov. for this new species that exhibits two distinct morphotypes in currently available collections, i.e. filiform or plumose assimilators. We also subsume C. tongaensis within the broadly distributed C. fastigiata, whose lectotype is also designated herein. In addition to Caulerpa wysorii sp. nov., we discovered yet another unknown denuded species from the Campeche Banks represented by a single specimen thus far. [ABSTRACT FROM AUTHOR]

Despite significant recent advances, our understanding of the diversity and phylogeny of coccoid green algae remains incomplete, partly because of the existence of numerous previously described taxa that are yet to be reinvestigated to clarify their identity and phylogenetic position. An essentially forgotten taxon is the genus Coleochlamys Korshikov, presently classified in the class Chlorophyceae. Here we present the results of our investigations of one new and four previously available strains identified as Coleochlamys. Based on morphological features and molecular evidence, the strains represented two clearly differentiated species: Co. apoda, the type species of the genus, and Co. oleifera, which are both epitypified in this study. The two species differ in cell shape and presence or absence of a cell wall extension resembling a papilla. They are also differentiated by multiple compensatory base changes (CBCs) in the ITS2 region. Our data support the previous proposal that the genera Rhopalocystis and Fusochloris are later synonyms of Coleochlamys, and additionally suggest that the algae originally described as Characium perforatum K.W. Lee & H.C. Bold and Rhopalocystis cucumis are conspecific with Co. apoda. Phylogenies of both 18S rRNA and rbcL genes place Coleochlamys in the class Trebouxiophyceae, in a clade with Microthamnion. Analysis of environmental DNA data has revealed the existence of at least one additional Coleochlamys species, and of a closely related sister lineage (potentially a separate genus) encountered in an Alaskan glacier. The occurrence data on Coleochlamys indicate that the genus includes psychrotolerant algae that may be common in cold environments worldwide. [ABSTRACT FROM AUTHOR]

The common green alga Trentepohlia sp. was found growing as a biofilm on galvanised iron lamp posts where it was exposed to high zinc levels and periodic desiccation. Its sole water sources were rainfall and dewfall. Photosynthesis studies using PAM techniques showed that the alga was a shade-adapted species with a very low optimum irradiance (Eopt) of about 90 μmol photons m−2 s−1, and ETRmax about 80 μmol e− g−1 chlorophyll-a s−1. But, within minutes, it recovered from desiccation (homiochlorophyllous). The alga has a high chlorophyll-b/a ratio (0.470 ± 0.016) and conspicuous chlorophyll-b absorption in vivo, but no measureable Zn-chlorophyll derivatives were found spectrophotometrically. Mannitol experiments using up to 1.5 Osmol kg−1 showed that photosynthesis in Trentepohlia sp. was highly resistant to water stress. Photosynthesis of Trentepohlia sp. was unaffected by pH even though the abundance of CO2 in the experimental medium dropped from 477 mmol m−3 at pH 5 to less than 1 mmol m−3 at pH 9. Thus, Trentepohlia sp. can use both CO2 and HCO3− as inorganic carbon sources. Acid pH (pH 5) did not increase toxicity of Zn. Trentepohlia sp. was resistant to added Zn with little effect on photosynthetic parameters even at 30 mol m−3 Zn. [ABSTRACT FROM AUTHOR]

Host–pathogen interactions involving microalgae have attracted more and more interest over the past decade. In order to understand interactions between those two partners and as basis of each single experiment, biological material in the form of cultures is crucial. Whereas the establishment of such cultures can by itself be very difficult and time-consuming, their subsequent maintenance often requires as much effort and manpower. The commercially utilised green microalgae Haematococcus pluvialis and Scenedesmus dimorphus are often challenged by the blastocladialean fungus Paraphysoderma sedebokerense, leading to culture crashes and economic loss. Currently, the interaction between alga and pathogen as well as the life cycle of the fungus are only partially understood. This represents a bottleneck and risk for the maintenance via continuous subcultivation. We here report the development of a cryopreservation protocol for Paraphysoderma sedebokerense and show its applicability to two different life stages of the pathogen. This protocol was validated on two different strains of Paraphysoderma. [ABSTRACT FROM AUTHOR]

The two genera Planktosphaeria (the type Pl. gelatinosa G.M.Smith) and Follicularia (the type F. paradoxalis Miller) have numerous chloroplast segments, each with a single pyrenoid. Autospore reproduction was described only in Planktosphaeria; whereas naked, biflagellate zoospores were known in Follicularia. The generic circumscription of Planktosphaeria was once changed to zoospore-producing forms based on P. gelatinosa sensu Starr UTEX 124, but some authors did not accept the amendment. Recent molecular analyses showed that Pl. botryoides and Pl. texensis belonged to a clade separate from Pl. gelatinosa sensu Starr, and then, the two former species were dealt with as members of Follicularia; whereas the latter was retained in Planktosphaeria. However, the ground for assigning these species to the two genera was not ascertained. To resolve the taxonomic confusions, 18S rDNA phylogenetic relationships, and morphological and ultrastructural features of selected species of these genera and closely related taxa were examined. It is concluded that identification of UTEX 124 as P. gelatinosa and the amendment of the generic circumscription of Planktosphaeria were not acceptable. By comparing the original line drawings of F. paradoxalis with morphological and ultrastructural features of other zoosporic species of Planktosphaeria, the former was inferred to belong to a clade including both Pl. gelatinosa sensu Starr UTEX124 and Pl. maxima (Sz-group), all of which were assigned to Follicularia. For Pl. botryoides and Pl. texensis (Rz-group), Herndonia gen. nov. was proposed, that was also characterised ultrastructurally. The taxonomic states of Pl. gelatinosa and other autosporic members of Schizochlamydaceae and Radiococcaceae are discussed. [ABSTRACT FROM AUTHOR]

Local isolates of the species-rich, fast-growing chlorophyte genus Oedogonium have been employed in outdoor biomass cultivation for industrial applications such as wastewater remediation, but such isolates may not express structural traits needed for definitive species identification by microscopy alone. We used maximum likelihood and Bayesian phylogenetic methods to evaluate molecular marker gene sequences derived from genomic sequences to characterise an industrial isolate, Oedogonium sp. Lake Mendota strain, which could not be reliably classified at species level using only morphology. Molecular markers evaluated were rbcL, 23S rDNA, 28S rDNA, 18S rDNA, and a sequence that included ITS1+5.8S rDNA+ITS2. All five markers distinguished the Lake Mendota strain from other Oedogonium accessions in GenBank. Using full genome sequences allowed the efficient acquisition of multiple types of marker sequences whose sequencing depth was known. In the absence of a classical species determination, these markers provided a taxonomic reference background for future genomic, biochemical, and other investigations of the local isolate. Local isolates are advantageous for outdoor industrial biomass cultivation applications because such isolates are already adapted to climatic conditions prevailing at cultivation sites. The results should encourage industrial use of local isolates of Oedogonium because these can be characterised by molecular markers even if structural features needed for accurate species determinations are not expressed. [ABSTRACT FROM AUTHOR]

Ancient lakes are centres of biological diversification that hold many examples of adaptive radiation and species flocks. The recently discovered species flock of Cladophoraceae in Lake Baikal is a group of green algae that exhibit low genetic divergence in ribosomal markers (LSU, SSU, and ITS), but wide morphological differentiation. Microsatellite markers showed evidence of polyploidy in this group, requiring alternate data scoring methodologies. In this study, we use two clustering methods (STRUCTURE and Gaussian Clustering) to delineate species within 15 distinct morphotaxa of the cladophoralean Baikal clade. The two cluster analyses produced comparable results, although subtle differences in the assignment of individuals were observed. Our results indicate that many morphologically distinguishable species are discrete genetic clusters supporting reproductive isolation. This is the case for Chaetomorpha (= Ch.) baicalensis, the attached form of Ch. curta, Ch. moniliformis, Cladophora (= Cl.) compacta, and Cl. kursanovii. The unattached form of Ch. curta and a species of Rhizoclonium are recovered as growth forms of Ch. moniliformis and the attached form of Ch. curta, respectively. The remaining morphotaxa were not clearly delimited. While we have evidence for polyploidy within this species flock, it was not possible to determine the ploidy level of each individual with accuracy as no correlation in the number of alleles was observed between loci. A more detailed study including other sources of data, such as nuclear DNA content or chromosome counts, is required to demonstrate the ploidy changes and their role in speciation in these species. [ABSTRACT FROM AUTHOR]

Two unidentified foliicolous algal strains were isolated from living Ficus leaves in a tropical rainforest of China. Morphological, ultrastructural, and molecular phylogenetic investigations of these strains indicated that they differ from each other but cluster together and represent a new lineage of Trebouxiophyceae in the Choricystis/Botryococcus clade. These strains had similar morphologies with solitary, fusiform, and slightly asymmetrical vegetative cells, a basal stalk, and smooth cell walls. Cells contained a single parietal chloroplast with a pyrenoid surrounded by several starch sheaths and penetrating thylakoids. Asexual reproduction occurred in both strains through the splitting of the mother cell wall into two autospores. Phylogenetic analysis based on 18S, ITS and rbcL showed the two strains as a distinct branch in the Choricystis/Botryococcus clade of the Trebouxiophyceae. Here, we describe the two strains as the new genus, Obliquicauda gen. nov., and two new species, Obliquicauda inflata sp. nov. and Obliquicauda apiculata sp. nov. [ABSTRACT FROM AUTHOR]

Research reports showed that linoleic acid is an allelochemical that can impact metabolic activity of microalgae. In this study, the effect of linoleic acid (LA) on astaxanthin accumulation in Chlorella sorokiniana was investigated under normal and light shock conditions. In normal autotrophic cultivation, maximum astaxanthin content was observed after 12 days in logarithmic growth with the addition of 32 µM LA; this was nearly twice as high as the control cultures without LA. After 15 days, chlorophyll a, astaxanthin to chlorophyll ratio, and biomass had changed by 0.6, 1.4 and 1.65 times relative to the control, respectively. When light stress was applied, addition of 32 µM LA enhanced astaxanthin concentration 1.3 times after 12 days, while chlorophyll a, astaxanthin to chlorophyll ratio and biomass had changed by 0.4, 1.8 and 2.6 times the control after 15 days, respectively. Accordingly, LA as a precursor to jasmonic and traumatic acids can have a role in the growth of C. sorokiniana, and production of astaxanthin and chlorophyll a in C. sorokiniana. This study demonstrates the potential of LA as an enhancer of algal astaxanthin production. [ABSTRACT FROM AUTHOR]

Molecular characterisation (using tufA and rbcL DNA sequences) of newly collected specimens of the genus Caulerpa in southern Australia identified 24 species and one variety, which, with the addition of four species and one variety recorded previously but not found during the present study, brings the total number of Caulerpa taxa in the region to 28 species and two varieties. Three new species are described based on molecular and morphological data: Caulerpa crispata comb. & stat. nov. (for C. longifolia f. crispata), Caulerpa coppejansii sp. nov., and Caulerpa perplexa sp. nov. Caulerpa coppejansii is a tropical West Pacific species and is included here due to its similarity to the southern Australian Caulerpa sedoides. Caulerpa perplexa is found in Western Australia and is a cryptic sister species of C. parvifolia Harvey from eastern Australia. The name Caulerpa muelleri is reinstated for C. flexilis var. muelleri. A new name, Caulerpa lucasii nom. nov., is proposed for Caulerpa annulata Lucas nom. illeg., a taxon shown to be distinct from Caulerpa hodgkinsoniae. Caulerpa corynephora and Caulerpa fergusonii are newly reported from the region, and a population of the potentially invasive Caulerpa cylindracea is reported from Portland, Victoria. An updated nomenclature is provided and reference tufA sequences are proposed, as well as an updated identification key for southern Australian Caulerpa species. [ABSTRACT FROM AUTHOR]

A strain of Volvox collected from Thailand produced a very large asexual spheroid with maximum diameter over 2 mm long. This Thai alga was identified as Volvox dissipatrix based on the delicate cytoplasmic bridges between somatic cells, gelatinous matrix structure, monoecious sexual spheroids and the original description reporting the large asexual spheroids. Comparative analyses of light and electron microscopic features and internal transcribed spacer 2 sequences of the nuclear ribosomal DNA of Thai and Australian monoecious strains of V. dissipatrix and their closely related heterothallic strains demonstrated that the latter represents a new species, Volvox zeikusii Nozaki. [ABSTRACT FROM AUTHOR]

The present study is the first to investigate the evolution of morphological variability and modularity of single (marginal) cells in two-dimensional colonial (coenobial) microscopic algae. Geometric morphometric methods were applied to eight monoclonal strains forming a common phylogenetic lineage, composed primarily of Pseudopediastrum boryanum varieties. Both cell parts, the cell body and projections, exhibited great morphological variability, which was impacted more or less by allometry in six strains. A relationship between phylogeny and morphology was not found. Asymmetry was concentrated in the projections. The pressure of neighbouring cells in a coenobium might have stabilised the symmetry of the cell body and prevented its asymmetric fluctuations. Both cell parts were separate modules, but a strain with distinct perforations in coenobia, resulting in less contact with the neighbouring cells, exhibited stronger cell integration, generally regarded as a possible constraint for evolutionary changes. This suggested that the pressure of neighbouring cells can also act as a factor favouring cell modularity and, thus, the morphological evolution of the marginal cells. [ABSTRACT FROM AUTHOR]

The hormone melatonin (MT) is produced by the pineal gland in animals and can also be found in plants and algae. MT regulates not only sleep, reduces the effects of jet lag, and has anti-aging properties in animals, but also eliminates intracellular reactive oxygen species and promotes vegetative growth in plants. However, research on its biological function in microalgae is still rare. The present study involved the construction of the Chlamydomonas reinhardtii expression vector pDBle-AANAT, which harbours the gene of one of the enzymes of the MT synthesis pathway, aralkylamine N-acetyltransferase (AANAT). The AANAT gene was introduced into the genome of the model microalga C. reinhardtii via glass bead transformation. The AANAT transgenic algal strain was identified by resistance screening, culture, and molecular biology methods. Changes in MT content between transformed algal strain and nontransformed algal strains were detected and the antioxidant capacity of the AANAT overexpressing algal strain was analysed under salt stress. The results showed that genetically engineered algae can increase the content of MT in algal cells by overexpressing AANAT. Under salt stress conditions, this can help to improve the enzymatic activity of the antioxidant system of algal cells and reduce membrane damage to counteract the adverse external stress. This enhances the self-protection ability of C. reinhardtii. This study reveals the effects of MT overproduction on the physiological functions of C. reinhardtii. Additionally, the potential functions of MT in the response of C. reinhardtii to stress have been elucidated, thus broadening the functional scope of MT in plants. [ABSTRACT FROM AUTHOR]

The recently described green algal genus Pseudorhizoclonium was erected for Rhizoclonium-like specimens that resolved as a separate clade from Rhizoclonium sensu stricto based on nuclear ribosomal DNA (SSU and LSU) data. We analysed 36 collections of Pseudorhizoclonium, including 18 new specimens, which resulted in a considerably extended distribution range that is mostly tropical to subtropical and includes Brazil, Madagascar, Philippines, French Polynesia, Panama, Tanzania, the Federated States of Micronesia, the Hawaiian Islands, Lord Howe Island (Australia) and temperate New Zealand. Ten distinct clades were resolved in phylogenetic analyses based on a combined SSU + LSU dataset, five of which were previously named as either Pseudorhizoclonium or Rhizoclonium species, and five of which likely represent novel lineages for this genus and are here named as new species (P. australe Boedeker, Leliaert & A.R.Sherwood, P. hawaiiense A.R.Sherwood, Boedeker & Leliaert, P. mangroviorum Boedeker, Leliaert & A.R.Sherwood, P. philippinense Leliaert, Boedeker & A.R.Sherwood, and P. subaerophilum A.R.Sherwood, Boedeker & Leliaert). Analysis of morphological characters demonstrated that although there was substantial overlap in character range for some lineages, others were distinct for one or more characters; however, morphological identification of the lineages is unreliable. The range of habitats in which these specimens were collected has been extended to include truly terrestrial areas and freshwater streams, which expands the known habitats of this genus beyond the original reports of mangroves, lagoons, and high intertidal areas. This genus represents an independent case of transition from marine into freshwater and terrestrial environments in the Cladophorales. Pseudorhizoclonium appears to have an unusually high tolerance for fluctuating environmental conditions, which may be related to the remarkable number of habitat transitions that have occurred within the genus. [ABSTRACT FROM AUTHOR]

Microalgae are a valuable source of biologically active compounds, e.g. lipids, carbohydrates, and pigments. In recent years, considerable interest has focused on unicellular photoautotrophic Chlorophyta. Green microalgae are characterized by their rapid growth and carbon dioxide binding in photosynthesis. Depending on the type of accumulated molecules (lipids or starch), photosynthetic cells can be used in the production of biodiesel, bioethanol, or biogas. However, low starch and lipid content may be an obstacle for using microalgal biomass as feedstocks for biofuels and bioproducts. Commercial cultivation of microalgae depends on a high content of valuable metabolites accumulated in cells. In this review, we evaluated factors controlling the synthesis and accumulation of lipids and starch, i.e. nitrogen and phosphorus availability and the impact of inorganic carbon, light, and temperature, under photoautotrophic growth conditions. The composition of microalgal biomass can be improved by various cultivation strategies. To increase the content of key metabolites, such as lipids and carbohydrates, the use of environmental stress factors is beneficial. The most important stress factor is nutrient stress, i.e. nitrogen and phosphorus deficiency. Achievement of a balance between optimal growth of microalgal biomass and high content of metabolites in cells is still a major challenge. Here, we analyse the factors controlling synthesis and accumulation of lipids and starch under photoautotrophic conditions. [ABSTRACT FROM AUTHOR]

The class Trebouxiophyceae is comprised of coccoid to ellipsoid unicells, filaments, blades and colony-forming species of green algae occurring in diverse terrestrial and aquatic environments. Some representatives have evolved parasitic heterotrophic lifestyles, others have been investigated for their biotechnological potential and others have evolved as integral components of lichen symbioses. In this review, we provide an overview of the current understanding of diversity, taxonomy and evolutionary context for the important lichen-forming algal class Trebouxiophyceae (Chlorophyta). In particular, we focus on members of the family Trebouxiaceae (Trebouxiales), the best-known, most widespread and most species-rich group of terrestrial, lichenised green algae. Recent investigations on the diversity of lichen phycobionts demonstrate the importance of implementing integrative taxonomic approaches. Therefore, combining analyses of morphological and anatomical traits with genetic data has improved our perspective of diversity in lichenised algae. More accurate recognition of diversity in Trebouxiophyceae will enhance our understanding of phylogenetic relationships and trait evolution, specimen identification in genomic and meta–bar-coding studies and patterns of specificity and selectivity among the lichen symbionts. We conclude with a discussion of the roles and transformative potential of high-throughput sequencing in research related to lichen-associated algae. [ABSTRACT FROM AUTHOR]

Long-lasting, slowly melting snowfields in mountainous regions are frequently populated by specialised microalgae whose diversity is still vastly underestimated. Cysts causing sub-surficial green snow were collected in the Austrian Alps, Tyrol, and morphologically accorded to the snow alga Scotiella cryophila sensu Chodat, initially described from Switzerland. The cytology and photobiology of this population were investigated to understand mechanisms of adaptation to the harsh habitat. Cysts of S. cryophila K-1 had secondary cell walls with pronounced rib-like surface structures and contained several small spherical plastids. The cytoplasm was dominated by lipid bodies, which developed reddish secondary pigmentation. Partial life cycle observations showed that daughter cells lacked structured cell walls. Cysts performed active photosynthesis at temperature conditions close to the freezing point and were photoinhibited at irradiances greater than 70 μmol m−2 s−1. This corresponded exactly to habitat conditions 20 to 40 cm below the snow surface. Phylogenetic analyses using 18S rDNA, rbcL and ITS2 rDNA sequences indicated that S. cryophila K-1 is related to Chloromonas, known to contain several snow algae. The taxon forms an independent lineage and is clearly genetically distinct from the type strain of Chloromonas rosae var. psychrophila from North America that is supposed to have morphologically identical cysts. For a taxonomic treatment including a species assignment of S. cryophila K-1 from Europe within Chloromonas, flagellates will have to be cultivated from cysts or from acquired field material for a detailed morphological description. Acquisition and genetic analysis of cysts that resemble S. cryophila from America could elucidate their relationship to European samples. [ABSTRACT FROM AUTHOR]

The order Trentepohliales represents one of the most prominent algal groups in terrestrial habitats but its taxonomy and phylogeny are still poorly understood. During a survey of Trentepohliales in different Brazilian biomes, some trentepohlialean populations were found in mixed forest localities growing on the bark of the gymnosperm Araucaria angustifolia. These populations formed orange patches with the typical habit of the genus Trentepohlia. The filaments consisted of cylindrical or swollen cells 4.0-10.2 μm wide and produced single apical globular gametangia and zoosporangia, with apical cells having a well-developed pectic cap. Molecular analysis based on the rbcL gene revealed that these populations represent a distinct clade, and based on the results, a new species, Trentepohlia araucariana, is described. [ABSTRACT FROM AUTHOR]

Codium pulvinatum sp. nov. (Bryopsidales, Chlorophyta) is described from the southern shores of Oman and from the Mediterranean shore of Israel. The new species has a pulvinate to mamillate-globose habit and long narrow utricles. Molecular data from the rbcL gene show that the species is distinct from closely related species, and concatenated rbcL and rps3-rpl16 sequence data show that it is not closely related to other species with similar external morphologies. The recent discovery of well-established populations of C. pulvinatum along the central Mediterranean coast of Israel suggests that it is a new Lessepsian migrant into the Mediterranean Sea. The ecology and invasion success of the genus Codium, now with four alien species reported for the Levantine Sea, and some ecological aspects are also discussed in light of the discovery of the new species. [ABSTRACT FROM AUTHOR]

Unicellular coccoid green algae are characterised by a high cryptic diversity, but such diversity is still poorly known, especially in terrestrial environments. The genus Jenufa, first described in 2011 from terrestrial habitats, currently includes three species: J. perforata, J. minuta and J. aeroterrestrica. We describe a new species, Jenufa lobulosa sp. nov. The type strain FACHB-2128 was isolated from sandstone surfaces in Nanning, Guangxi Province, a subtropical area in southwestern China, and the cultured material was examined using light and electron microscopy. It shared representative features of the genus: a parietal perforated chloroplast with several lobes, no pyrenoids, and asexual reproduction via autospores. However, J. lobulosa differed from congeners in the mean size of its vegetative cells and autosporangia, the number of autospores and cell wall thickness. Phylogenetic analyses of 18S rDNA and rbcL sequences showed that strain FACHB-2128 belonged to the Jenufa clade of the Chlorophyceae, forming an independent lineage and differing from any known species. The position of strain FACHB-2128 within Jenufa was also supported by ITS2 rDNA sequences. [ABSTRACT FROM AUTHOR]

Chlorella kessleri is a green alga that grows photoautotrophically, heterotrophically and mixotrophically. To explore the mechanism of glucose metabolism at the molecular level, cDNA (GenBank ID KF011248) encoding glucokinase (named CkeGK) from C. kessleri was cloned and sequenced. The Ckegk cDNA was 1167 base pairs (bp) long, with an open reading frame of 1089 bp encoding 362 amino acids with a calculated molecular mass of 38.98 kDa and an estimated isoelectric point of 4.78. Multiple alignment analysis revealed that the deduced amino acid sequence of Ckegk shared a high identity of 65%-78% with corresponding glucokinase from other eukaryotes. The catalytic motifs of glucokinase were detected in the amino acid sequence of Ckegk. Under different trophic modes, the transcriptional profiles of Ckegk showed that it could be up-regulated under a heterotrophic culture condition but not under a mixotrophic culture condition. Furthermore, the gene was differentially expressed in Escherichia coli, and biochemical characterisation was determined. According to SDS-PAGE, the purified recombinant CkeGK showed a single band about 43.0 kDa, which correlated with the theoretical molecular weight predictions. Biochemical analysis showed that CkeGK was stable at 40°C and 50°C, but it lost 60% of its activity after incubation for 40 min at 60°C. The optimal pH for the activity of CkeGK was 9.0, and the Km and Vmax for ATP were 0.1168 mM and 5.346 nmol ml−1 min−1 and for glucose were 0.1465 mM and 6.022 nmol ml−1 min−1. [ABSTRACT FROM AUTHOR]

In molecular phylogenetic trees of zoospore-producing unicellular chlorophycean algae, well-resolved lineages often do not correspond to current taxonomic categories, and therefore characterising diagnostic morphological traits of lineages can be challenging. We employed a phylogenetic framework to examine the evolution of light microscopic (LM) and transmission electron microscopic (TEM) features in the phylogroup Moewusinia and a related genus and then assessed the features that could be used to diagnose lineages. Most LM characters were homoplasies, but particular character states uniquely supported lineages. Autospores arranged in isobilateral tetrads made up a suitable generic feature; whereas, tetrahedral tetrads or indefinite groups of autospores were not. Some chloroplast phenotypes lacked phylogenetic signal, especially the sponge-like form previously used to define genera. Pyrenoid types characterised clades at different depths. TEM features of zoospores (i.e. papillar shape, cell wall layers, nuclear position and components of the basal apparatus) were generally consistent with clades. The sawhorse-shaped distal connecting fibre with beam-like extensions was characteristic of some phylogroups. Ultrastructural components of sexual reproduction may serve as a marker at deeper phylogenetic depths. Within Moewusinia, the saline habitat was restricted to one clade. In total, nine phylogenetic clades were defined at generic rank using phenotypic traits. Three new genera were proposed: Eubrownia gen. nov., with the new combinations E. aggregata, E. dissociata, E. illinoisensis and E. isobilateralis; Parachlorococcum turfosum gen. & sp. nov.; and Alvikia gen. nov., with the new combination Al. littoralis. Chlorococcum ( Cc.) was emended, with the new combinations Cc. aerium, Cc. macropyrenoidosum and Cc. vacuolatum. Tetracystis with the type species T. aeria was abandoned. Spongiococcum was emended with the new combination S. aplanosporum. [ABSTRACT FROM AUTHOR]

Here we showed enrichment of the orthologue of the plant specific Ca2+ binding protein CAS in Chlamydomonas reinhardtii (CrCAS) in both the thylakoids and the eyespot. Ca2+ binding to recombinant CrCAS was analysed for the first time in detail. Binding of 45Ca2+ (2.9 μM) occurred in the presence of an excess of Mg2+ (5 mM) and was not affected by variation in pH from 6.8 to 8.0. Competition experiments with the Ca2+ antagonists La3+ (50 μM) and unlabelled Ca2+ (5 mM) indicated that CrCAS probably acts as a low-affinity/high-capacity Ca2+ binding protein. Fe2+ (5 μM) had no effect on 45Ca2+ binding. To elucidate a possible role of CrCAS in the phototactic signalling cascade, knockdown and CrCAS overexpressing lines were generated. All 17 knockdown lines quickly reverted, making a detailed analysis impossible. In contrast, overexpressing lines were stable for at least 6 to 9 mo. Four of these lines with overexpression levels between 169% and 270% were analysed in detail for their phototactic behaviour. At low photon fluence rates, all showed an initial positive phototactic orientation. After a few minutes, however, they switched to an orientation away from the light source. The threshold fluence rate for this switch was determined and negatively correlated with the CrCAS overexpression level. In contrast, the negative phototactic behaviour of the lines at higher light intensities was unaffected, and empty vector control lines responded like the wild-type, pointing to the specificity of this effect. These results indicate that C. reinhardtii CAS, in addition to its known roles in acclimation of photosynthesis to high light, is also involved in adaptation responses to low light at an intermediate time scale and also affects processes outside the chloroplast. [ABSTRACT FROM AUTHOR]

In this study of northern Patagonia in Argentina, we examined the annual cycle of the epiphyte composition and abundance on Ulva sp. with respect to intertidal elevation, season and position on host. We found spatial segregation in most environmental gradients. Local environmental conditions, intertidal levels, seasons and portion of host thalli had specific patterns of algal epiphytic community. The host population exhibited seasonality and differential morphological attributes according to the intertidal elevation. Thalli of Ulva sp. had the highest maximum diameters and were heavier in spring and summer at the upper elevation. Epiphytes were more abundant growing on host thalli at middle elevations. Epiphytic Dinophyceae, Chlorophyceae and Cyanophyceae presented clear seasonality. Epiphyte abundances were related to periods with high seawater temperature, long days and high radiation. Lyngbya sp., Cocconeis sp., Navicula spp., Rhabdonema arcuatum, Stylonema alsidii and Myrionema strangulans had the highest frequency. The highest epiphyte abundance was observed in holdfasts, with M. strangulans having the highest frequency and cover. These results are relevant to commercial aquaculture ventures for food and feed sources and application in bioremediation. [ABSTRACT FROM AUTHOR]

The use of 18S rDNA sequences for inferring phylogenies, in particular for higher taxonomic level analysis, has a long tradition in phycology. Similar to ITS2, the 18S rDNA displays a conserved secondary structure that could be used simultaneously with the primary sequence to increase the amount of information used when inferring phylogenetic relationships. Sequence-structure phylogenetics is already established for ITS2 research. Secondary structures no longer simply guide alignments and trees but are used simultaneously by encoding the sequence-structure information into a 12-letter alphabet. We used the knowledge gathered from the extensive body of ITS2 research regarding sequence-structure phylogenetics and applied it to 18S rRNA data; we present THESES db, the Algae 18S rDNA Sequence-Structure Database (), which contains sequences and their individual secondary structures for three major groups of algae (Chlorophyta, Bacillariophyta and Rhodophyta). This database was designed to serve as the starting point for future 18S rDNA sequence-structure based phylogenetic analyses that will eventually extend beyond phycology. One hundred phylogenetic trees generated from 18S sequence-only datasets and from parallel 18S sequence-structure datasets were compared for each taxon analyzed in this study (diatoms, green algae and red algae). Half of the comparisons produced trees with different topologies that frequently related to the status of sister genera. Using the lineage information for each species as listed in GenBank, we determined that the sequence-structure approach resolved a genus as monophyletic, while the sequence-only approach failed to do so in comparisons that comprised 3% of the cases examined. The reverse was true for a total of 8.3% of the comparisons that we generated. Future work, both in our labs and among the broader phycological community, will provide additional data to test the accuracy and robustness of a sequence-structure approach at different taxonomic ranks. [ABSTRACT FROM AUTHOR]