RESUMO
Improved methods for the extraction of eicosapentaenoic acid (EPA), an essential and economically important polyunsaturated fatty acid, are urgently required. However, lipid extraction rates using food-grade solvents such as ethanol are usually low. To improve the ethanol-based extraction rate, and to elucidate the relevant mechanisms, we used cellulase and laccase to treat powdered Nannochloropsis, one of the most promising microalgal sources of EPA. Cellulase and laccase synergistically increased lipid yields by 69.31% and lipid EPA content by 42.63%, by degrading the amorphous hemicellulose and cellulose, improving crystallinity, and promoting the release and extraction of lysodiacylglyceryltrimethylhomoserine. Scanning electron microscopy showed that cell morphology was substantially altered, with cell-wall rupture, loss of cell boundaries, and the release of intracellular substances. In conclusion, Nannochloropsis lipid yields may be directly linked to cell-wall hemicellulose structure, and enzymatic treatment to alter this may improve lipid yields.
Assuntos
Celulase/química , Lacase/química , Lipídeos/química , Estramenópilas , Parede Celular/química , Celulose/química , Etanol/química , Lipidômica , Microscopia Eletrônica de Varredura , Polissacarídeos/química , Solventes/química , Estramenópilas/química , Estramenópilas/citologia , Estramenópilas/ultraestruturaRESUMO
Eicosapentaenoic acid (EPA) from freeze-dried biomass of Nannochloropsis oceanica microalgae resists ruminal biohydrogenation in vitro, but in vivo demonstration is needed. Therefore, the present study was designed to test the rumen protective effects of N. oceanica in lambs. Twenty-eight lambs were assigned to one of four diets: Control (C); and C diets supplemented with: 1.2% Nannochloropsis sp. oil (O); 12.3% spray-dried N. oceanica (SD); or 9.2% N. oceanica (FD), to achieve 3 g EPA /kg dry matter. Lambs were slaughtered after 3 weeks and digestive contents and ruminal wall samples were collected. EPA concentration in the rumen of lambs fed FD was about 50% higher than lambs fed SD or O diets. Nevertheless, the high levels of EPA in cecum and faeces of animals fed N. oceanica biomass, independently of the drying method, suggests that EPA was not completely released and absorbed in the small intestine. Furthermore, supplementation with EPA sources also affected the ruminal biohydrogenation of C18 fatty acids, mitigating the shift from the t10 biohydrogenation pathways to the t11 pathways compared to the Control diet. Overall, our results demonstrate that FD N. oceanica biomass is a natural rumen-protected source of EPA to ruminants.
Assuntos
Ácido Eicosapentaenoico/metabolismo , Rúmen/metabolismo , Carneiro Doméstico/metabolismo , Estramenópilas/química , Ração Animal/análise , Animais , Biomassa , Dieta/veterinária , Suplementos Nutricionais , Digestão , Ácidos Graxos/metabolismo , Liofilização , Microbioma Gastrointestinal , Absorção Intestinal , Masculino , Microalgas/química , Microalgas/ultraestrutura , Microscopia Eletrônica de Varredura , Rúmen/microbiologia , Carneiro Doméstico/microbiologia , Estramenópilas/ultraestruturaRESUMO
Thraustochytrids are marine protists that naturally accumulate triacylglycerol with long chains of polyunsaturated fatty acids, such as ω3-docosahexaenoic acid (DHA). They represent a sustainable response to the increasing demand for these "essential" fatty acids (FAs). Following an attempt to transform a strain of Aurantiochytrium limacinum, we serendipitously isolated a clone that did not incorporate any recombinant DNA but contained two to three times more DHA than the original strain. Metabolic analyses indicated a deficit in FA catabolism. However, whole transcriptome analysis did not show down-regulation of genes involved in FA catabolism. Genome sequencing revealed extensive DNA deletion in one allele encoding a putative peroxisomal adenylate transporter. Phylogenetic analyses and yeast complementation experiments confirmed the gene as a peroxisomal adenylate nucleotide transporter (AlANT1), homologous to yeast ScANT1 and plant peroxisomal adenylate nucleotide carrier AtPNC genes. In yeast and plants, a deletion of the peroxisomal adenylate transporter inhibits FA breakdown and induces FA accumulation, a phenotype similar to that described here. In response to this metabolic event, several compensatory mechanisms were observed. In particular, genes involved in FA biosynthesis were upregulated, also contributing to the high FA accumulation. These results support AlANT1 as a promising target for enhancing DHA production in Thraustochytrids.
Assuntos
Trifosfato de Adenosina/metabolismo , Ácidos Graxos/metabolismo , Mutação/genética , Óleos/metabolismo , Peroxissomos/metabolismo , Estramenópilas/metabolismo , Transporte Biológico , Perfilação da Expressão Gênica , Genoma , Modelos Biológicos , Filogenia , Estramenópilas/genética , Estramenópilas/crescimento & desenvolvimento , Estramenópilas/ultraestrutura , Transcriptoma/genéticaRESUMO
The stramenopiles are a large and diverse group of eukaryotes that possess various lifestyles required to thrive in a broad array of environments. The stramenopiles branch with the alveolates, rhizarians, and telonemids, forming the supergroup TSAR. Here, we present a new genus and species of aquatic nanoflagellated stramenopile: Mediocremonas mediterraneus, a free-swimming heterotrophic predator. M. mediterraneus cell bodies measure between 2.0-4.0 µm in length and 1.2-3.7 µm in width, possessing two flagella and an oval body morphology. The growth and grazing rate of M. mediterraneus in batch cultures ranges from 0.68 to 1.83 d-1 and 1.99 to 5.38 bacteria/h, respectively. M. mediterraneus was found to be 93.9% phylogenetically similar with Developayella elegans and 94.7% with Develorapax marinus, two members within the class Developea. The phylogenetic position of the Developea and the ability of M. mediterraneus to remain in culture make it a good candidate for further genomic studies that could help us to better understand phagotrophy in marine systems as well as the transition from heterotrophy to phototrophy within the stramenopiles.
Assuntos
Estramenópilas/classificação , Estramenópilas/citologia , Microscopia Eletrônica de Varredura , Filogenia , RNA de Algas/análise , RNA Ribossômico 16S/análise , Estramenópilas/genética , Estramenópilas/ultraestruturaRESUMO
A unicellular, heterotrophic, eukaryotic parasite was isolated from nearshore Arctic marine sediment in association with the diatom Pleurosigma sp. The parasite possessed ectoplasmic threads that could penetrate diatom frustules. Healthy and reproducing Pleurosigma cultures would begin to collapse within a week following the introduction of this parasite. The parasite (2-10 µm diameter) could reproduce epibiotically with biflagellate zoospores, as well as binary division inside and outside the diatom host. While the parasite grew, diatom intracellular content disappeared. Evaluation of electron micrographs from co-cultures revealed the presence of hollow tubular processes and amorphic cells that could transcend the diatom frustule, generally at the girdle band, as well as typical thraustochytrid ultrastructure, such as the presence of bothrosomes. After nucleotide extraction, amplification, and cloning, database queries of DNA revealed closest molecular affinity to environmental thraustochytrid clone sequences. Testing of phylogenetic hypotheses consistently grouped this unknown parasite within the Thraustochytriidae on a distinct branch within the environmental sequence clade Lab19. Reclassification of Arctic high-throughput sequencing data, with appended reference datasets that included this diatom parasite, indicated that the majority of thraustochytrid sequences, previously binned as unclassifiable stramenopiles, are allied to this new isolate. Based on the combined information acquired from electron microscopy, life history, and phylogenetic testing, this unknown isolate is described as a novel species and genus.
Assuntos
Diatomáceas/parasitologia , RNA Ribossômico 18S/genética , Análise de Sequência de DNA/métodos , Estramenópilas/classificação , Animais , Regiões Árticas , DNA Ribossômico/genética , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/ultraestrutura , Sequenciamento de Nucleotídeos em Larga Escala , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Filogenia , Estramenópilas/genética , Estramenópilas/ultraestruturaRESUMO
The redescription of Opalina obtrigonoidea Metcalf, 1923, collected from the rectum of the toads Duttaphrynus melanostictus, is presented in this paper based on detailed morphological information and molecular data. Our results revealed that O. obtrigonoidea varies greatly in body dimensions. Its morphological characteristics allow its differentiation from Opalina undulata. Surprisingly, we sequenced its SSU rDNA-ITS1-5.8S rDNA-ITS2-LSU rDNA (5' end) and found the SSU rDNA of O. obtrigonoidea is nearly identical to that of O. undulata. However, there are differences in both the ITS1 and ITS2 regions that allow their distinction and confirm the morphological differences. Our results indicate that O. obtrigonoidea and O. undulata are closely related species in which morphological and genetic markers have evolved at different speeds. Due to this, the SSU rDNA gene may not be a valid marker for inter-species identification in Opalina, but the ITS is a valid marker for differentiating species in this genus.
Assuntos
Bufonidae/parasitologia , Estramenópilas/classificação , Animais , China , DNA Espaçador Ribossômico/análise , Marcadores Genéticos , Microscopia Eletrônica de Varredura/veterinária , Filogenia , Análise de Sequência de DNA/veterinária , Estramenópilas/citologia , Estramenópilas/ultraestruturaRESUMO
Thraustochytrid cells attach to their food via ectoplasmic nets (ENs). Here, we analyzed the cause and effect relationship between the various forms and functions of ENs of Schizochytrium aggregatum. The ENs spread out over a large area forming a fine network to efficiently search for the experimental food source. After recognizing the experimental food source, the ENs that attached to the food source became thicker, and net elements developed. The thick ENs on the surface at the attachment site were enveloped in dense materials (fibrous materials), which were visualized as fibrous layers under a transmission electron microscope. Experiments using fluorescein diacetate and the fluorescent glucose analog 2-NBDG showed that the production rate of hydrolytic enzymes and the absorption rate of glucose by ENs of S. aggregatum increased in the presence of an experimental food source. Our results reveal that ENs change their shape and function according to the presence/absence of a food source.
Assuntos
Citoplasma/metabolismo , Estramenópilas/fisiologia , Adesão Celular , Comportamento Alimentar , Microscopia Eletrônica de Transmissão , Nutrientes/metabolismo , Estramenópilas/ultraestruturaRESUMO
Thraustochytrids are single cell marine eukaryotes that produce large amounts of polyunsaturated fatty acids such as docosahexaenoic acid. In the present study, we report the visualization of endoplasmic reticulum (ER) and mitochondria in a type strain of the thraustochytrid, Aurantiochytrium limacinum ATCC MYA-1381, using the enhanced green fluorescent protein (EGFP) with specific targeting/retaining signals. We expressed the egfp gene with ER targeting/retaining signals from A. limacinum calreticulin or BiP/GRP78 in the thraustochytrid, resulting in the distribution of EGFP signals at the perinuclear region and near lipid droplets. ER-Tracker™ Red, an authentic fluorescent probe for the visualization of ER in mammalian cells, also stained the same region. We observed small lipid droplets generated from the visualized ER in the early growth phase of cell culture. Expression of the egfp gene with the mitochondria targeting signal from A. limacinum cytochrome c oxidase resulted in the localization of EGFP near the plasma membrane. The distribution of EGFP signals coincided with that of MitoTracker® Red CMXRos, which is used to visualize mitochondria in eukaryotes. The ER and mitochondria of A. limacinum were visualized for the first time by EGFP with thraustochytrid cell organelle-specific targeting/retaining signals. These results will contribute to classification of the intracellular localization of proteins expressed in ER and mitochondria as well as analyses of these cell organelles in thraustochytrids.
Assuntos
Retículo Endoplasmático/metabolismo , Proteínas de Fluorescência Verde/metabolismo , Mitocôndrias/metabolismo , Estramenópilas/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Proteínas de Fluorescência Verde/genética , Estramenópilas/ultraestruturaRESUMO
A culture of a unicellular heterotrophic eukaryote was established from pollen-baited seawater acquired from the nearshore environment in Tromsø, Norway. Light microscopy revealed the production of ectoplasmic nets and reproduction by biflagellated zoospores, as well as binary division. After culturing and subsequent nucleotide extraction, database queries of the isolate's 18S small ribosomal subunit coding region identified closest molecular affinity to Aplanochytrium haliotidis, a pathogen of abalone. Testing of phylogenetic hypotheses consistently grouped our unknown isolate and A. haliotidis among the homoplasious thraustochytrids. Transmission electron microscopy revealed complex cell walls comprised of electron-dense lamella that formed protuberances, some associated with bothrosomes. Co-culturing experiments with the marine fungus Penicillium brevicompactum revealed prolonged interactions with hyphal strands. Based on the combined information acquired from electron microscopy, life history information, and phylogenetic testing, we describe our unknown isolate as a novel species. To resolve molecular polyphyly within the aplanochytrids, we erect a gen. nov. that circumscribes our novel isolate and the former A. haliotidis within the thraustochytrids.
Assuntos
Estramenópilas/genética , Processos Heterotróficos , Microscopia Eletrônica de Transmissão , Noruega , Filogenia , Água do Mar/microbiologia , Estramenópilas/classificação , Estramenópilas/isolamento & purificação , Estramenópilas/ultraestruturaRESUMO
A complex of closely related Mallomonas taxa belonging to the section Papillosae, M. kalinae Rezácová and M. rasilis Dürrschmidt, has been studied in detail by molecular and morphometric methods. Our investigations uncovered the existence of a new species found in water bodies in Vietnam, which we describe here as Mallomonas furtiva sp. nov. This taxon is morphologically very similar to M. kalinae, from which it differs by minute, but statistically significant morphological differences on the structure of silica scales. Indeed, the principal component analysis of morphological traits measured on silica scales significantly separates all three species in the complex. Mallomonas kalinae and M. furtiva differ by number of papillae on the shield and the dome, as well as by the scale sizes. Likewise, Mallomonas rasilis and M. furtiva are primarily differentiated by the absence of submarginal anterior ribs on silica scales of the former species. Phylogenetic analyses showed that Mallomonas furtiva is closely related to M. kalinae, with which it formed a highly supported lineage. Distribution patterns of all three studied taxa are further discussed.
Assuntos
Microbiota , Estramenópilas/classificação , Proteínas de Algas/análise , DNA de Algas/análise , DNA Ribossômico/análise , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Filogenia , Estramenópilas/genética , Estramenópilas/ultraestrutura , Vietnã , Áreas AlagadasRESUMO
Thraustochytrids, a heterotrophic fungus-like clade of Stramenopiles, are becoming an increasingly important source of polyunsaturated fatty acids (PUFAs) for biotechnological industries. PUFA rich oils from these organisms are subsequently referred to in some literature and marketing sources as being derived from 'algae', in spite of their non-photosynthetic source organism. In this review, we attempt to disentangle the evolutionary relationship of the Thraustochytrids from other Protists, demonstrating that there is no scientific basis for the aforementioned misnomer. Some research has previously suggested that the ancestor of the Stramenopiles may have been photosynthetic, and subsequently lost their plastids in multiple lineages. The placement of the Thraustochytrids within the Stramenopiles and their possible plastid loss may have been a source of obfuscation. It is becoming increasingly evident that the common ancestor of the Stramenopiles was not photosynthetic, and that only the Ochrophyte lineage later engulfed a plastid via higher order endosymbiosis. Because all basal lineages of Stramenopiles are non-plastidial heterotrophs, including the Thraustochytrids, there remains no phylogenetic, biological, or ecological justification for the term 'algae' to be applied to Thraustochytrids or their products.
Assuntos
Filogenia , Rodófitas/classificação , Estramenópilas/classificação , Evolução Biológica , Ácidos Graxos Insaturados/metabolismo , Funções Verossimilhança , Fotossíntese , Plastídeos , Rodófitas/fisiologia , Rodófitas/ultraestrutura , Estramenópilas/fisiologia , Estramenópilas/ultraestruturaRESUMO
There are many eukaryotic lineages that are exclusively composed of environmental sequences and lack information about which species are included. Regarding stramenopiles, at least 18 environmental lineages, known as marine stramenopiles (MAST), have been recognized. Since each MAST lineage forms deep branches in the stramenopiles, the characterization of MAST members is key to understanding the diversity and evolution of stramenopiles. In this study, we established a culture of Pseudophyllomitus vesiculosus, which is a poorly studied phagotrophic flagellate of uncertain taxonomic position. Our molecular phylogenetic analyses based on small subunit ribosomal RNA gene sequences robustly supported the inclusion of P. vesiculosus in the MAST-6 clade. Our microscopic observations indicated that P. vesiculosus shared characteristics with stramenopiles, including an anterior flagellum that exhibits sinusoidal waves and bears tubular mastigonemes. The flagellar apparatus of P. vesiculosus was also similar to that of other stramenopiles in having a transitional helix and five microtubular roots (R1-R4 and S tubules) including R2 that split into two bands. On the other hand, P. vesiculosus was distinguished from other deep-branching stramenopiles by the combination of flagellar apparatus characteristics. Based on the phylogenetic analyses and microscopic observations, we established Pseudophyllomitidae fam. nov in stramenopiles.
Assuntos
Filogenia , Estramenópilas/classificação , Japão , RNA Ribossômico/genética , Análise de Sequência de RNA , Estramenópilas/citologia , Estramenópilas/genética , Estramenópilas/ultraestruturaRESUMO
Cepedea longa Bezzenberger, 1904, collected from Fejervarya limnocharis (Amphibia, Anura, Ranidae) from Honghu Lake, Hubei Province, China in May-July 2016, is described at both light and transmission electron microscope levels. This is the first electron microscopic study of this species. Cepedea longa possesses a developed fibrillar skeletal system, composed of longitudinal fibrillar bands and transversal fibrils as well as numerous thin microfibrils dispersed in the endoplasm, which may play an important role in morphogenesis and offer some resilience to deformations of the cell. Longitudinal microfibrils are polarizing elements of kineties, bordering the somatic kineties on the left side and possibly responsible for kinetosome alignment. Two types of vesicles exist in the somatic cortex: globular endocytotic vesicles and flattened exocytotic vesicles. As to the nuclei of C. longa, a thick microfibrillar layer was observed to attach to the cytoplasmic face of the nuclear envelope. This fact suggests no necessary connection between the presence of this microfibrillar layer and the number of nuclei. In addition, some unknown tightly-packed microtubular structures in the nucleoplasm were observed for the first time in opalinids; neither their nature nor physiological significance is known. A detailed list of all reported Cepedea species is included.
Assuntos
Anuros/parasitologia , Infecções/veterinária , Estramenópilas/ultraestrutura , Animais , Infecções/microbiologia , Microscopia Eletrônica de TransmissãoRESUMO
The parmalean algae possess a siliceous wall and represent the sister lineage of diatoms; they are thought to be a key group for understanding the evolution of diatoms. Diatoms possess well-characterized and unique mitotic structures, but the mitotic apparatus of Parmales is still unknown. We observed the microtubule (MT) array during interphase and mitosis in Triparma laevis using TEM. The interphase cells had four or five centrioles (â¼80 nm in length), from which MTs emanated toward the cytoplasm. In prophase, the bundle of MTs arose at an extranuclear site. The position of centrioles with respect to an MT bundle changed during its elongation. Centrioles were observed on the lateral side of a shorter MT bundle (â¼590 nm) and on either side of an extended MT bundle (â¼700 nm). In metaphase, the spindle consisted of two types of MTs-MT bundle that passed through a cytoplasmic tunnel in the center of the nucleus and single MTs (possibly kinetochore MTs) that extended from the poles into the nucleus. The nuclear envelope disappeared only at the regions where the kinetochore MTs penetrated. In telophase, daughter chromosomes migrated toward opposite poles, and the MT bundle was observed between segregating chromosomes. These observations showed that MT nucleation does not always occur at the periphery of centrioles through cell cycle and that the spindle of T. laevis has a similar configuration to that of diatoms.
Assuntos
Fuso Acromático/metabolismo , Estramenópilas/metabolismo , Núcleo Celular/efeitos dos fármacos , Núcleo Celular/metabolismo , Células Cultivadas , Centríolos/efeitos dos fármacos , Centríolos/metabolismo , Interfase/efeitos dos fármacos , Metáfase/efeitos dos fármacos , Microtúbulos/efeitos dos fármacos , Microtúbulos/metabolismo , Modelos Biológicos , Silício/farmacologia , Fuso Acromático/efeitos dos fármacos , Estramenópilas/citologia , Estramenópilas/ultraestruturaRESUMO
To date, the life stages of pelagophytes have been poorly described. This study describes the ability of Aureoumbra lagunensis to enter a resting stage in response to environmental stressors including high temperature, nutrient depletion, and darkness as well as their ability to revert from resting cells back to vegetative cells after exposure to optimal light, temperature, and nutrient conditions. Resting cells became round in shape and larger in size, filled with red accumulation bodies, had smaller and fewer plastids, more vacuolar space, contained lower concentrations of chl a and RNA, displayed reduced photosynthetic efficiency, and lower respiration rates relative to vegetative cells. Analysis of vegetative and resting cells using Raman microspectrometry indicated resting cells were enriched in sterols within red accumulation bodies and were depleted in pigments relative to vegetative cells. Upon reverting to vegetative cells, cells increased their chl a content, photosynthetic efficiency, respiration rate, and growth rate and lost accumulation bodies as they became smaller. The time required for resting cells to resume vegetative growth was proportional to both the duration and temperature of dark storage, possibly due to higher metabolic demands on stored energy (sterols) reserves during longer period of storage and/or storage at higher temperature (20°C vs. 10°C). Resting cells kept in the dark at 10°C for 7 months readily reverted back to vegetative cells when transferred to optimal conditions. Thus, the ability of Aureoumbra to form a resting stage likely enables them to form annual blooms within subtropic ecosystems, resist temperature extremes, and may facilitate geographic expansion via anthropogenic transport.
Assuntos
Proliferação Nociva de Algas , Estramenópilas/fisiologia , Microscopia Eletrônica de Transmissão , Estramenópilas/química , Estramenópilas/crescimento & desenvolvimento , Estramenópilas/ultraestruturaRESUMO
A novel Diplophrys-like organism, Fibrophrys columna, was isolated from Hiuchigaike Pond in Japan. F. columna showed a nearly orbicular or broadly elliptical cell shape and has fine filamentous, branching ectoplasmic elements emanating from both polar ends of the cell. Cells also contain orange, amber, or colorless lipid bodies. Although its whole cell morphology resembles that of the genus Diplophrys, Fibrophrys is clearly distinct from Diplophrys on the basis of 18S rDNA sequences. Molecular phylogenetic analysis showed a close relationship of F. columna with Amphifila marina, and its sequence is similar to many environmental stramenopile sequences. The cells of F. columna measured 5.0-8.3×5.6-10.3µm and sometimes possessed hernia-like prongs instead of filamentous ectoplasmic elements. An axis-like electron-dense body was observed in the mitochondria. We also studied the ultrastructure of another Fibrophrys strain, Fibrophrys sp. E-1, which is different from the type strain of F. columna. A ladder-like pattern was recognized in the outer part of unidentified cytoplasmic membranes connected with the mitochondria. The unidentified cytoplasmic membranes were connected to the nuclear, lipid body, and mitochondrial outer membranes. We propose a new genus, Fibrophrys, and a new species, F. columna, based on these ultrastructural and molecular features.
Assuntos
Lagoas/parasitologia , Estramenópilas/classificação , Japão , Microscopia Eletrônica de Transmissão , Filogenia , RNA Ribossômico 18S/genética , Especificidade da Espécie , Estramenópilas/citologia , Estramenópilas/genética , Estramenópilas/ultraestruturaRESUMO
A statistical mixture design approach was used to investigate the effects of cell wall degrading enzymes on the recovery of lipids from Nannochloropsis sp. A preliminary screening of potentially suitable enzyme preparations, including lysozyme, cellulase and different types of hemicellulases, was carried out. The most effective preparations were then taken as basic components for the formulation of enzyme mixtures. Optimized ternary mixtures consisting of cellulase and two hemicellulases were obtained which allowed the recovery of up to 37.2g of lipids per 100g of dry biomass. SEM and TEM images of the enzymatically treated microalga revealed extensive cell damage, with degradation of the cell wall and release of intracellular material. Overall, the results obtained demonstrate that the mixture design method can be used to prepare cell wall degrading enzyme cocktails that can significantly improve the recovery of lipids or other valuable components from microalgae.
Assuntos
Lipídeos/isolamento & purificação , Microalgas/metabolismo , Estramenópilas/metabolismo , Biomassa , Parede Celular/metabolismo , Parede Celular/ultraestrutura , Celulase/farmacologia , Glicosídeo Hidrolases/farmacologia , Metabolismo dos Lipídeos , Lipídeos/análise , Microalgas/efeitos dos fármacos , Microalgas/ultraestrutura , Muramidase/farmacologia , Estramenópilas/ultraestruturaRESUMO
Most swarmers (swimming cells) of the stramenopile group, ranging from unicellular protist to giant kelps (brown algae), have two heterogeneous flagella: a long anterior flagellum (AF) and a relatively shorter posterior flagellum (PF). These flagellated cells often exhibit phototaxis upon light stimulation, although the mechanism by which how the phototactic response is regulated remains largely unknown. A flavoprotein concentrating at the paraflagellar body (PFB) on the basal part of the PF, which can emit green autofluorescence under blue light irradiance, has been proposed as a possible blue light photoreceptor for brown algal phototaxis although the nature of the flavoprotein still remains elusive. Recently, we identified helmchrome as a PF-specific flavoprotein protein in a LC-MS/MS-based proteomics study of brown algal flagella (Fu et al. 2014). To verify the conservation of helmchrome, in the present study, the absence or presence and the localization of helmchrome in swarmers of various algal species were investigated. The results showed that helmchrome was only detected in phototactic swarmers but not the non-phototactic ones of the stramenopile group. Electron microscopy further revealed that the helmchrome detectable swarmers bear a conserved PFB-eyespot complex, which may serve as structural basis for light sensing. It is speculated that all three conserved properties: helmchrome, the PFB structure, and the eyespot apparatus, will be essential parts for phototaxis of stramenopile swarmers.
Assuntos
Flagelos/ultraestrutura , Flavoproteínas/metabolismo , Fototaxia/fisiologia , Estramenópilas/fisiologia , Clorófitas/fisiologia , Clorófitas/ultraestrutura , Flagelos/fisiologia , Flavoproteínas/química , Luz , Microscopia Eletrônica de Transmissão , Phaeophyceae/fisiologia , Fotorreceptores de Plantas/química , Fotorreceptores de Plantas/metabolismo , Filogenia , Domínios Proteicos , Proteômica/métodos , Estramenópilas/ultraestrutura , Espectrometria de Massas em TandemRESUMO
Colourless, nonscaled chrysophytes comprise morphologically similar or even indistinguishable flagellates which are important bacterivors in water and soil crucial for ecosystem functioning. However, phylogenetic analyses indicate a multiple origin of such colourless, nonscaled flagellate lineages. These flagellates are often referred to as "Spumella-like flagellates" in ecological and biogeographic studies. Although this denomination reflects an assumed polyphyly, it obscures the phylogenetic and taxonomic diversity of this important flagellate group and, thus, hinders progress in lineage- and taxon-specific ecological surveys. The smallest representatives of colourless chrysophytes have been addressed in very few taxonomic studies although they are among the dominant flagellates in field communities. To overcome the blurred picture and set the field for further investigation in biogeography and ecology of the organisms in question, we studied a set of strains of specifically small, colourless, nonscaled chrysomonad flagellates by means of electron microscopy and molecular analyses. They were isolated by a filtration-acclimatisation approach focusing on flagellates of around 5 µm. We present the phylogenetic position of eight different lineages on both the ordinal and the generic level. Accordingly, we describe the new genera Apoikiospumella, Chromulinospumella, Segregatospumella, Cornospumella and Acrispumella Boenigk et Grossmann n. g. and different species within them.
Assuntos
Biodiversidade , Chrysophyta/classificação , Filogenia , Estramenópilas/classificação , Chrysophyta/genética , Chrysophyta/ultraestrutura , Cadeia Alimentar , Microscopia Eletrônica , Reação em Cadeia da Polimerase , Água do Mar , Análise de Sequência de DNA , Estramenópilas/genética , Estramenópilas/ultraestruturaRESUMO
A novel facultative anaerobic bacterivorous nanoflagellate was isolated from the water just below the permanent oxic-anoxic interface of the meromictic Lake Suigetsu, Japan. We characterized the isolate using light and transmission electron microscopy and molecular phylogenetic analyses inferred from 18S rDNA sequences. The phylogenetic analyses showed that the isolate belonged to class Placididea (stramenopiles). The isolate showed key ultrastructural features of the Placididea, such as flagellar hairs with two unequal terminal filaments, microtubular root 2 changing in shape from an arced to an acute-angled shape, and a lack of an x-fiber in root 2. However, the isolate had a single helix in the flagellar transition region, which is a double helix in the two known placidid nanoflagellates Placidia cafeteriopsis and Wobblia lunata. Moreover, the isolate had different intracellular features compared with these two genera, such as the arrangement of basal bodies, the components of the flagellar apparatus, the number of mitochondria, and the absence (or presence) of paranuclear bodies. The 18S rDNA sequence was also phylogenetically distant from the clades of the known Placididae W. lunata and P. cafeteriopsis. Consequently, the newly isolated nanoflagellate was described as Suigetsumonas clinomigrationis gen. et sp. nov.