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LM and TEM micrographs of Ankistrodesmus nannoselene strain SAG 202-6 in culture. Scale bars: (A) 10 lm; (B, C) 1 lm. (A) Young cells; the arrowhead indicates the empty mother cell wall remnants. (B) Longitudinal section showing the naked spherical pyrenoid (star) in the central part of the chloroplast; (C) diagonal section showing the naked multiformed pyrenoid (stars). c, chloroplast; m, mitochondrion.
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The generic concept of coccoid green algae exhibiting a crescent‐shaped morphotype is evaluated using SSU rRNA gene sequence analyses and light and electron microscopical observations. These common chlorophytes evolved polyphyletically in 10 different clades of the Chlorophyceae and three clades of the Trebouxiophyceae. Six clades are assigned to k...
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... cells with two or four serially arranged au- tospores (Fig. 4B). The cell wall was widened before autospore release. Under TEM, the pyrenoid matrix was covered by thylakoids, but not by starch grains; however, thylakoids penetrated the pyrenoid (Fig. 4C). A. nannoselene was characterized by half- moon-shaped or croissant-shaped solitary cells (Fig. 5). Under LM, no pyrenoids were discernible. However, under TEM one or two spherical or com- pound naked pyrenoids were visible in the central part of the chloroplast (Fig. 5, B and ...
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... but not by starch grains; however, thylakoids penetrated the pyrenoid (Fig. 4C). A. nannoselene was characterized by half- moon-shaped or croissant-shaped solitary cells (Fig. 5). Under LM, no pyrenoids were discernible. However, under TEM one or two spherical or com- pound naked pyrenoids were visible in the central part of the chloroplast (Fig. 5, B and ...
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Citations
... This can be explained by the fact that the sequence of 18S rDNA gene is highly conserved in many microalgal species, increasing the importance of using other DNA-based barcodes for higher resolution in the identification of closely related algae. 34,26,38 In contrast, the substitution rate of the ITS region is higher in green microalgae, making it a good marker for identification 24,33,35,39 along with the 18S rDNA gene marker. ...
In light of the rapid and extreme changes in climate and the steady depletion of natural resources, there is an urgent need to find innovative and sustainable solutions to these problems. Microorganisms such as microalgae can offer viable solutions to these challenges. Proper investment in such organisms requires the identification of the algal species that inhabit the region. Therefore, this study aimed to isolate and molecularly characterize green microalgae that inhabit freshwater at different locations in the governorates of Irbid and Ajloun in the northern region of Jordan. Water samples collected from these regions were used to isolate single colonies, some of which exhibited different morphological characteristics. Genomic DNA was extracted from the isolates and used as a template for PCR amplification of the 18S ribosomal DNA gene (18S rDNA) and the internal transcribed spacer (ITS) region. Phylogenetic trees were constructed based on 18S rDNA and ITS PCR product sequences, which were used to identify the isolates at the genus level. The obtained isolates belonged to three genera; Coelastrella, Desmodesmus, and Monoraphidium. The latter species has not been previously reported in Jordan.
... The greatest U signal in the midgut of the U Ref -exposed daphnid was observed in a 10 μm, partially digested algae cell ( Figure 5C), Raphidocelis subcapitata, which are known to effectively bind bioavailable U species. 54,55 Although the test organisms were removed from feed prior to exposure, complete evacuation of the intestine did not occur and the presence of the U-bearing algal cell demonstrated the relationship between U uptake and binding to gut contents. This observation highlights inherent constraints of whole-body burden measurements that are not able to differentiate between tissue uptake and intestinally confined U present in the lumen. ...
Micro- and nanoscopic X-ray techniques were used to investigate the relationship between uranium (U) tissue distributions and adverse effects to the digestive tract of aquatic model organism Daphnia magna following uranium nanoparticle (UNP) exposure. X-ray absorption computed tomography measurements of intact daphnids exposed to sublethal concentrations of UNPs or a U reference solution (URef) showed adverse morphological changes to the midgut and the hepatic ceca. Histological analyses of exposed organisms revealed a high proportion of abnormal and irregularly shaped intestinal epithelial cells. Disruption of the hepatic ceca and midgut epithelial tissues implied digestive functions and intestinal barriers were compromised. Synchrotron-based micro X-ray fluorescence (XRF) elemental mapping identified U co-localized with morphological changes, with substantial accumulation of U in the lumen as well as in the epithelial tissues. Utilizing high-resolution nano-XRF, 400-1000 nm sized U particulates could be identified throughout the midgut and within hepatic ceca cells, coinciding with tissue damages. The results highlight disruption of intestinal function as an important mode of action of acute U toxicity in D. magna and that midgut epithelial cells as well as the hepatic ceca are key target organs.
... Raphidocelis subcapitata (Korshikov) . This crescent-like morphotypes are almost undifferentiable under the light microscope and the traditional taxonomic concepts for genera within the Selenastraceae are questionable after molecular phylogeny [7][8][9][10]. ...
... The employment of molecular tools, mainly the studies on the 18S rDNA, have untangled the coccoid green algae phylogeny and revealed new genera and species by disclosing cryptic taxa or including ones usually overlooked by microscopic analysis not only within the Selenastraceae but also in unrelated lineages like Chlorella and Parachlorella [7][8][9][10]25,26]. Such natural system has changed the research in phycology, stimulating taxonomists to understand the phytoplanktonic diversity in a quite different perspective and unveiling the diversity and evolutive history of many phototrophic eukaryotes. ...
... Two different alignments were constructed for the phylogenetic analyses (18S and rbcL) with the newly obtained sequences and additional sequences obtained from NCBI (http://www.ncbi.nlm.nih.gov/). Reference sequences representing the different lineages of the Selenastraceae and sequences for the outgroup were selected on the basis of previous publications [2,7,9,10] (More information see Table 1). Previous publications indicated that Bracteacoccaceae, Scenedesmaceae and Hydrodictyaceae members were suitable as an outgroup for the phylogeny of Selenastraceae [10,34]. ...
The simple morphology of the members of the family Selenastraceae, common in freshwater phytoplankton, has led to misidentifications. But the use of molecular tools is untangling their phylogeny and unveiling new genera and species hidden under the same morphotype or overlooked by microscopic analysis. Here we propose a description of Viridiparva madeirensis gen. et sp. nov., a small Selenastraceae member, based on the study of three strains by light, scanning and transmission microscopy and 18S rDNA and rbcL phylogenies. The phylogenetic analyses by 18S rDNA and rbcL show, respectively, that the closest relatives to Viridiparva madeirensis are Monoraphidium dybowskii and Raphidocelis microscopica, but with no or low statistical support. V. madeirensis is smaller than M. dybowski and has no cell wall incrustations typical for Raphidocelis. Thus, phylogeny and morphological analyses indicate a novel lineage within Selenastraceae. Furthermore, also reinforce the necessary revision of the genera within Selenastraceae, as Monoraphidium and Raphidocelis. Therefore study contributes to clarify the phylogeny and taxonomy of the family and add genetic sequences of neglected nanophytoplankton to GenBank, including one strain with known potential for biodiesel production.
... Lots of taxonomic advances have proceeded in the family since its description in 1903 [72]. Even if the monophyly of Selenastraceae was elucidated [73][74][75] the necessity for genera revision within the family is pointed out, since molecular data do not support morphological identification and disjunction [74,75]. TAU-MAC 1210 exhibited features of the genus Monoraphidium; unicellular microalga without mucilage, fusiform, curved to sigmoid, narrow or acute at the ends (Figure 6d-f) [76], including one parietal chloroplast with an embedded naked pyrenoid, without starch cover (Figure 7f,g). ...
... Lots of taxonomic advances have proceeded in the family since its description in 1903 [72]. Even if the monophyly of Selenastraceae was elucidated [73][74][75] the necessity for genera revision within the family is pointed out, since molecular data do not support morphological identification and disjunction [74,75]. TAU-MAC 1210 exhibited features of the genus Monoraphidium; unicellular microalga without mucilage, fusiform, curved to sigmoid, narrow or acute at the ends (Figure 6d-f) [76], including one parietal chloroplast with an embedded naked pyrenoid, without starch cover (Figure 7f,g). ...
In the large and morphologically diverse phylum of Chlorophyta, new taxa are discovered every year and their phylogenetic relationships are reconstructed by the incorporation of molecular phylogenetic methods into traditional taxonomy. Herein, we aim to contribute to the photosynthetic microorganisms’ diversity knowledge in the Mediterranean area, a relatively unexplored ecoregion with high diversity. Based on a polyphasic approach, 18 Chlorophyta isolates were investigated and characterized. Morphological characteristics and ultrastructure, the phylogeny based on 18S rRNA gene (small subunit ribosomal RNA), 18S–28S internal transcribed spacer (ITS region), and the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit region (rbcL gene), support establishing four new genera (Nomia, Ava, Akraea, Lilaea) and five new species (Spongiosarcinopsis limneus, N. picochloropsia, Av. limnothalassea, Ak. chliaropsychia, and L. pamvotia) belonging to orders Sphaeropleales, Chlorellales, and Chlamydomonadales. For some of them, this is the first report of their occurrence in specific aquatic environments.
... chlorococcorum f. majus can infect multiple genera of Selenastraceae, such as Ankistrodesmus, Kirchneriella, and Monoraphidium (Gromov and Mamkaeva 1970;this study). However, these algal genera are polyphyletic (Garcia da Silva et al. 2017;Krienitz et al. 2011). Therefore, hosts of Ap. parallelum and Ap. ...
Aphelids (phylum Aphelida = Aphelidiomycota) are intracellular parasitoids of algae and represent one of the early-diverging or sister lineages of the kingdom Fungi. Although aphelids are a small group comprising four genera and 17 species, molecular phylogenetic analyses revealed that numerous environmental DNA sequences represent undescribed lineages, indicating their hidden diversity. Here, we investigated a novel aphelid strain, KS114, that parasitizes selenastracean green algae. KS114 exhibited a life cycle typical of aphelids and produced posteriorly uniflagellate zoospores that resembled those of Aphelidium chlorococcorum f. majus in possessing a single apical filopodium but could be distinguished by ultrastructure features. In KS114, the kinetosome and nonflagellated centriole were aligned in parallel, a unique characteristic among the known aphelids. Kinetid-associated structures, such as fibrillar root and microtubules, were not found in the zoospores of KS114. In the molecular phylogeny of nuc 18S rDNA sequences, KS114 clustered with two environmental sequences and was distinct from all other sequenced species. Based on these results, we describe this aphelid as a new species, Aphelidium parallelum.
http://www.zoobank.org/urn:lsid:zoobank.org:act:3CB658DB-1F12-41EF-A57D-2CBFCDE6A49A
... Partial sequence of the 18S rRNA gene is a widely accepted and commonly used approach in microalgae identification [46][47][48][49]. However, the analyses of sequence, phylogeny and morphology were inconclusive to identify all microalgal strains to the species level in this study. ...
... UQL1_20) did not form a distinct clade. This finding supports the view of Fawley et al. [55], and Krienitz et al. [47,56], where species of the family Selenastraceae under existing taxonomic criteria display a polyphyletic nature. Further analyses using a combination of morphological characteristics, including ultrastructure [46,47,51] and DNA sequence including the internal transcribed spacer 2 (ITS2) rDNA, which has higher substitution rates in comparing with 18S rRNA gene [43,47,48,50,56], are required for discrimination of algal species. ...
... This finding supports the view of Fawley et al. [55], and Krienitz et al. [47,56], where species of the family Selenastraceae under existing taxonomic criteria display a polyphyletic nature. Further analyses using a combination of morphological characteristics, including ultrastructure [46,47,51] and DNA sequence including the internal transcribed spacer 2 (ITS2) rDNA, which has higher substitution rates in comparing with 18S rRNA gene [43,47,48,50,56], are required for discrimination of algal species. ...
Microalgae contain high-value biochemical compounds including fatty acids (FA), protein and carotenoids, and are promising bioresources to enhance nutrition of food and animal feed. Important requirements for commercial strains are rapid growth and high productivities of desirable compounds. As these traits are believed to be found in aquatic environments with fluctuating conditions, we collected microalgae from marine and freshwater environments that are subjected to eutrophication and/or tidal fluctuations. Using this directed approach, 40 monoalgal cultures were isolated and 25 identified through 18S rDNA sequencing and morphological characterization. Based on their high growth rates (0.28–0.60 day−1) and biomass productivities (0.25–0.44 g L−1day−1) in commercial fertilizer under standardized conditions, six new strains were selected. Scenedesmus sp. GW63 produced quality FA-rich biomass with high omega-3 polyunsaturated FA (28.5% of total FA (TFA)) contents, especially α-linolenic acid (ALA; 20.0% of TFA) with a very low n-6/n-3 ratio (0.4), and high FA productivity (32.6 mg L−1 day−1). A high protein productivity (34.5 mg L−1 day−1) made Desmodesmus sp. UQL1_26 (33.4% of dry weight (DW)) attractive as potential protein-rich feed and nutrition supplement. Monoraphidium convolutum GW5 displayed valuable carotenoid production (0.8% DW) with high carotenoid accumulation capability (0.8 mg L−1 day−1). This research provides a pathway for fast-tracking the selection of high-performing local microalgae from different environments for nutraceuticals, functional foods and animal feed applications.
... A. Optical microscopy image at 40x objective of a culture of R. subcapitata at INERIS facilities. B. and C. TEM images of longitudinal section and cross-section respectively; chloroplast (c), nucleus (n), starch grain (s), pyrenoid (star); scale 1µm(Krienitz et al., 2011). ...
Due to their singular properties, the use of manufactured nanomaterials (NMs) has experienced a substantial success in the last decades. The growing production of these increasingly varied substances raises concern, in particular regarding their fate in environmental compartments and their potential effects on aquatic organisms. This thesis studied, in a systematic and innovative way, the interactions (adsorption, uptake, elimination and effects) of a set of twelve metal oxides NMs with different physicochemical characteristics, with different freshwater organisms representing primary producers (microalgae) and primary consumers (microinvertebrates). First, the interactions of three different species of microalgae with the NMs were characterized using a method developed for this purpose. Then, the uptake and elimination behaviors of the NMs in the filter-feeding microcrustacean D. magna were established. Subsequently, transcriptomic analyses allowed to determine the early molecular effects of NMs at the cellular and individual level of these organisms. Finally, the possibility of establishing relationships between the physicochemical properties of NMs and their behavior towards aquatic organisms was studied. The main findings of this work are finally intended to provide information on the importance of biological parameters in the NMs grouping processes of and to fill in the existing gaps in the risk assessment of NMs.
... The characteristic, more or less crescent outer cell shape of Thorsmoerkia curvula, is not unique; several green microalgae similar in size and morphology from likewise habitats are known, within and outside the Trebouxiophyceae. Krienitz et al. (2011) already showed the polyphyletic origin of crescent-shaped green algae by molecular means, and recognized them in three clades of the Trebouxiophyceae and in ten clades of Selenastraceae. In the latter, the new species resembled the terrestrial Monoraphidium pusillum (Ettl and Gärtner 2013). ...
... rDNA region of T. curvula was highly divergent compared to other trebouxiophycean taxa explored so far. Nevertheless, according to the 18S rDNA and rbcL gene-based phylogenies (Figs. 3 and 4), T. curvula is not closely related to any of the morphologically similar trebouxiophycean taxa, including young cells of "E-form" of Watanabea reniformis (Hovde et al. 2018) or Neocystis mucosa (Krienitz et al. 2011). In the last years, several new lineages of trebouxiophycean algae have been discovered including the description of new genera, suggesting that the diversity of this group is still underexplored (Neustupa et al 2013;Song et al 2015;Vančurová et al. 2015;Ulrich and Röske 2018;Darienko and Pröschold 2019). ...
A terrestrial green alga was isolated at Iceland, and the strain (SAG 2627) was described for its morphology and phylogenetic position and tested for biotechnological capabilities. Cells had a distinctly curved, crescent shape with conical poles and a single parietal chloroplast. Phylogenetic analyses of 18S rDNA and rbc L markers placed the strain into the Trebouxiophyceae (Chlorophyta). The alga turned out to belong to an independent lineage without an obvious sister group within the Trebouxiophyceae. Based on morphological and phylogenetic data, the strain was described as a new genus and species, Thorsmoerkia curvula gen. et sp. nov. Biomass was generated in column reactors and subsequently screened for promising metabolites. Growth was optimized by pH-regulated, episodic CO 2 supplement during the logarithmic growth-phase, and half of the biomass was thereafter exposed to nitrogen and phosphate depletion. The biomass yield reached up to 53.5 mg L ⁻¹ day ⁻¹ . Fatty acid (FA) production peaked at 24 mg L ⁻¹ day ⁻¹ and up to 83% of all FAs were unsaturated. At the end of the log phase, approximately 45% of dry mass were lipids, including eicosapentaenoic acid. Carotenoid production reached up to 2.94 mg L ⁻¹ day ⁻¹ but it was halted during the stress phase. The N-linked glycans of glycoproteins were assessed to reveal chemotaxonomic patterns. The study demonstrated that new microalgae can be found at Iceland, potentially suitable for applied purposes. The advantage of T. curvula is its robustness and that significant amounts of lipids are already accumulated during log phase, making a subsequent stress exposure dispensable.
... Nephrochlamys was resolved within Selenastraceae F.F.Blackman & Tansley, whereas strains attributed to Nephrocytium, including N. agardhianum, formed an incertae sedis lineage in the Sphaeropleales Luerss. (Štenclová, 2013;Liu & al., 2017;Štenclová & al., 2017) or Chlorophyceae (Vieira & al., 2016), which agrees with the suggestion of a polyphyletic origin of the crescent-shaped coccoid green algae (Krienitz & al., 2011). ...
... Some of these taxa excluded from Oocystaceae were placed in several lineages in Sphaeropleales as Nephrochlamys, Rhombocystis (Krienitz & al., 2011) and Nephrocytium (Liu & al., 2017;Štenclová & al., 2017). Other morphologically similar genera, such as Ecdysichlamys (Oocystaceae according to Komárek & Fott, 1983) and Rayssiella Edelst. ...
The common planktonic green algal genus Nephrocytium was traditionally assumed to have a close relationship with the genus Oocystis and accordingly has been included in the family Oocystaceae. Although the position of Nephrocytium within the Oocystaceae has differed according to some authors over the years, its inclusion in the family has not been questioned. Following molecular studies of Oocystis, the Oocystaceae (including Nephrocytium) was removed from the class Chlorophyceae and placed in the Trebouxiophyceae. However, recent molecular studies of some of the former Oocystaceae members have returned them to the Chlorophyceae. These studies suggested the placement of Nephrocytium in the Sphaeropleales, but no taxonomic positioning within the order has been determined for the genus. The relocation of Nephrocytium agrees with a strong morphological trait – it lacks the oocystaceaean multilayered ultrastructure of the cell wall. Based on molecular markers (18S rDNA and tufA), and optical and electron microscopy, the present study aimed to establish the relationships of the genus within the Sphaeropleales. The results support the recognition of a new family, the Nephrocytiaceae, to accommodate Nephrocytium. Furthermore, we have carried out a review of previously described Nephrocytium species and based on morphological and molecular data we propose the description of Nephrocytium vieirae sp. nov.
... The test organism was Raphidocelis subcapitata (= Pseudokirchneriella subcapitata = Selenastrum capricornutum) [31] from an axenic culture maintained by Aquatic BioSystems, Fort Collins, Colorado. The green algae population was incubated in the unamended ambient water samples in a static system for a common time period of at least 96 hours or until the maximum standing crop was achieved. ...
Successful eutrophication control strategies need to address the limiting nutrient. We conducted a battery of laboratory and in situ nutrient-limitation tests with waters collected from 9 streams in an agricultural region of the upper Snake River basin, Idaho, USA. Laboratory tests used the green alga Raphidocelis subcapitata , the macrophyte Lemna minor (duckweed) with native epiphytes, and in situ nutrient-limitation tests of periphyton were conducted with nutrient-diffusing substrates (NDS). In the duckweed/epiphyte test, P saturation occurred when concentrations reached about 100 μg/L. Chlorophyll a in epiphytic periphyton was stimulated at low P additions and by about 100 μg/L P, epiphytic periphyton chlorophyll a appeared to be P saturated. Both duckweed and epiphyte response patterns with total N were weaker but suggested a growth stimulation threshold for duckweed when total N concentrations exceeded about 300 μg/L and approached saturation at the highest N concentration tested, 1300 μg/L. Nutrient uptake by epiphytes and macrophytes removed up to 70 and 90% of the N and P, respectively. The green algae and the NDS nutrient-limitation test results were mostly congruent; N and P co-limitation was the most frequent result for both test series. Across all tests, when N:P molar ratios >30 (mass ratios >14), algae or macrophyte growth was P limited; N limitation was observed at N:P molar ratios up to 23 (mass ratios up to 10). A comparison of ambient periphyton chlorophyll a concentrations with chlorophyll a accrued on control artificial substrates in N-limited streams, suggests that total N concentrations associated with a periphyton chlorophyll a benchmark for desirable or undesirable conditions for recreation would be about 600 to 1000 μg/L total N, respectively. For P-limited streams, the corresponding benchmark concentrations were about 50 to 90 μg/L total P, respectively. Our approach of integrating controlled experiments and matched biomonitoring field surveys was cost effective and more informative than either approach alone.
