RESUMO
Temporal programs synchronised with the daily cycle are of adaptive importance for organisms exposed to periodic fluctuations. This study deepens into several aspects of the exogenous and endogenous nature of microbial grazers. We investigated the diel rhythms of cell division and feeding activity of four marine protists under different light regimes. In particular, we tested if the feeding cycle of protistan grazers could be mediated by a light-aided enhancement of prey digestion, and also explored the consequences of cell division on diel feeding rhythms. Cell division occurred at night for the heterotrophic dinoflagellates Gyrodinium dominans and Oxyrrhis marina. In contrast, the mixotrophic dinoflagellate Karlodinium armiger and the ciliate Strombidium sp. mostly divided during the day. Additionally, a significant diurnal feeding rhythm was observed in all species. When exposed to continuous darkness, nearly all species maintained the cell division rhythm, but lost the feeding cycle within several hours/days (with the exception of O. marina that kept the rhythm for 9.5 days). Additional feeding experiments under continuous light also showed the same pattern. We conclude that the feeding rhythms of protistan grazers are generally regulated not by cell division nor by the enhancement of digestion by light. Our study, moreover, indicates that the cell division cycle is under endogenous control, whereas an external trigger is required to maintain the feeding rhythm, at least for most of the species studied here.
Assuntos
Cilióforos/fisiologia , Dinoflagellida/fisiologia , Divisão Celular/efeitos da radiação , Cilióforos/efeitos da radiação , Dinoflagellida/efeitos da radiação , Processos Heterotróficos , LuzRESUMO
The influences of intensity and repeated exposure to ultraviolet-B radiation (UVB), photoreactivating repair radiation (PRR), and temperature on the scuticociliate Parauronema acutum were explored under laboratory conditions. Population growth was negatively affected after exposure to the equivalent of one sunny summer day of ambient UVB, especially in the absence of PRR. Repeated daily exposure to UVB severely compromised ciliate survival. UVB-exposed treatments without PRR recovered slower and reached lower final abundances than treatments receiving PRR. Reducing the daily UVB exposure approximately 25% improved ciliate recovery after exposure. In the single exposure treatments, temperature effects were not consistent, except that growth was slowest for control and treatments at the lowest temperature (15 °C). These data suggest that dark repair and/or photoprotection are present in P. acutum, but photoenzymatic repair was the more effective mechanism in reversing UVB damage. Repeated exposure treatments without PRR had zero or declining growth at all temperatures (15, 20 and 25 °C), as did those with PRR at 15 °C. Significant temperature/dose differences were identified in the repeated exposure treatments; ciliates subjected to the higher UVB intensity with PRR survived only at 25 °C, while ciliate populations under reduced UVB increased at 20 and 25 °C.
Assuntos
Cilióforos/efeitos da radiação , Cilióforos/crescimento & desenvolvimento , Ecossistema , Temperatura , Raios UltravioletaRESUMO
The step-up photophobic response of the heterotrich ciliate Blepharisma japonicum is mediated by a hypericinic pigment, blepharismin, which is not present in any of the known six families of photoreceptors, namely rhodopsins, phytochromes, xanthopsins, cryptochromes, phototropins, and BLUF proteins. Upon irradiation, native cells become light-adapted (blue) by converting blepharismin into the photochemically stable oxyblepharismin (OxyBP). So far, OxyBP has been investigated mainly from a photophysical point of view in vitro, either alone or complexed with proteins. In this work, we exploit the vivid fluorescence of OxyBP to characterize its lifetime emission in blue B. Japonicum cells, on account of the recognized role of the fluorescence lifetime to provide physicochemical insights into the fluorophore environment at the nanoscale. In a biological context, OxyBP modifies its emission lifetime as compared to isotropic media. The phasor approach to fluorescence lifetime microscopy in confocal mode highlights that fluorescence originates from two excited states, whose relative balance changes throughout the cell body. Additionally, Cilia and kinetids, i.e., the organelles involved in photomovement, display lifetime asymmetry between the anterior and posterior part of the cell. From these data, some hypotheses on the phototransduction mechanism are proposed.
Assuntos
Cilióforos/química , Cilióforos/efeitos da radiação , Cor , Luz , Perileno/análogos & derivados , Células Fotorreceptoras/química , Células Fotorreceptoras/efeitos da radiação , Cilióforos/citologia , Microscopia de Fluorescência , Estrutura Molecular , Perileno/química , Perileno/efeitos da radiação , Processos FotoquímicosRESUMO
Morphofunctional disorders in unicellular aquatic protozoa - Spirostomum ambiguum infusorians after 30-, 60-, and 360-min exposure in electromagnetic field at a radiation frequency of 1 GHz and energy flow density of 50 µW/cm(2) were analyzed by intravital computer morphometry. Significant disorders in morphometric values correlated with low mobility of the protozoa. The results suggested the use of intravital computer morphometry on the protozoa for early diagnosis of radiation-induced effects of the mobile communication electromagnetic field, for example, low mobility of spermatozoa.
Assuntos
Cilióforos/citologia , Cilióforos/efeitos da radiação , Campos Eletromagnéticos/efeitos adversos , Telefone Celular , Ondas de Rádio/efeitos adversosRESUMO
The psychrophilic ciliate Euplotes focardii inhabits the shallow marine coastal sediments of Antarctica, where, over millions of years of evolution, it has reached a strict molecular adaptation to such a constant-temperature environment (about -2 °C). This long evolution at sub-zero temperatures has made E. focardii unable to respond to heat stress with the activation of its heat shock protein (hsp) 70 genes. These genes can, however, be expressed in response to other stresses, like the oxidative one, thus indicating that the molecular adaptation has exclusively altered the heat stress signaling pathways, while it has preserved hsp70 gene activation in response to other environmental stressors. Since radiative stress has proved to be affine to oxidative stress in several organisms, we investigated the capability of UV radiation to induce hsp70 transcription. E. focardii cell cultures were exposed to several different irradiation regimes, ranging from visible only to a mixture of visible, UV-A and UV-B. The irradiation values of each spectral band have been set to be comparable with those recorded in a typical Antarctic spring. Using Northern blot analysis, we measured the expression level of hsp70 immediately after irradiation (0-h-labeled samples), 1 h, and 2 h from the end of the irradiation. Surprisingly, our results showed that besides UV radiation, the visible light was also able to induce hsp70 expression in E. focardii. Moreover, spectrophotometric measurements have revealed no detectable endogenous pigments in E. focardii, making it difficult to propose a possible explanation for the visible light induction of its hsp70 genes. Further research is needed to conclusively clarify this point.
Assuntos
Cilióforos/fisiologia , Euplotes/fisiologia , Luz , Raios Ultravioleta , Aclimatação , Adaptação Fisiológica , Cilióforos/efeitos da radiação , Euplotes/efeitos da radiaçãoRESUMO
The authors review the findings of researches into the effects of low-dose ionizing irradiation on diverse biological objects (embryonic Japanese quails, Aspergillus niger, Spirostomum ambiguum Ehrbg., mesenchymal stem cells from mouse marrow, dry higher plants seeds, blood lymphocytes from pilots and cosmonauts). Model experiments with chronic exposure to ionizing radiation doses comparable with the measurements inside orbital vehicles and estimations for trips through the interplanetary space resulted in morphological disorders (embryonic Japanese quails, Aspergillus niger), radiation hormesis (Aspergillus niger, MSCs from mouse marrow), increase in the seed germination rate, inhibition of Spirostomum spontaneous activity, DNA damages, chromosomal aberrations, and increase of the blood lymphocytes reactivity to additional radiation loading. These facts give grounds to assume that the crucial factor in the radiation outcomes is changes in liquid medium. In other words, during extended orbiting within the magnetosphere region and interplanetary missions ionizing radiation affects primarily liquids of organism and, secondarily, its morphofunctional structures.
Assuntos
Medicina Aeroespacial , Astronautas , Radiação Ionizante , Voo Espacial , Animais , Aspergillus niger/efeitos da radiação , Cilióforos/efeitos da radiação , Coturnix , Humanos , Linfócitos/metabolismo , Linfócitos/efeitos da radiação , Células-Tronco Mesenquimais/metabolismo , Células-Tronco Mesenquimais/efeitos da radiação , Camundongos , Federação Russa , SementesRESUMO
By using NMR spectroscopy, a non-invasive investigation technique, we performed in vivo experiments aimed at uncovering the metabolic pathways involved in the early response of Fabrea salina cells to ultraviolet (UV) radiation. This hypersaline ciliate was chosen as a model organism because of its well-known high resistance to UV radiation. Identical cell samples were exposed to visible radiation only (control samples, CS) and to UV-B + UV-A + visible radiation (treated samples, TS), and NMR spectra of in vivo cells were collected at different exposure times. Resonances were identified through one- and two-dimensional experiments. To compare experiments performed at variable irradiation times on different culture batches, metabolite signals affected by the UV exposure were normalized to corresponding intensity at τ = 0, the zero exposure time. The most affected metabolites are all osmoprotectants, namely, choline, glycine-betaine, betaines, ectoine, proline, α-trehalose and sucrose. The time course of these signals presents qualitative differences between CS and TS, and most of these osmoprotectants tend to accumulate significantly in TS in a UV dose-dependent manner. A picture of the immediate stress response of F. salina against UV radiation in terms of osmoprotection, water retention and salting-out prevention is described.
Assuntos
Cilióforos/metabolismo , Cilióforos/efeitos da radiação , Raios Ultravioleta , Diamino Aminoácidos/metabolismo , Betaína/metabolismo , Membrana Celular/metabolismo , Membrana Celular/efeitos da radiação , Cilióforos/citologia , Glicina/metabolismo , Espectroscopia de Ressonância Magnética , Prolina/metabolismo , Sacarose/metabolismo , Fatores de Tempo , Trealose/metabolismoRESUMO
Fabrea salina is a hypersaline ciliate that is known to be among the strongest ultraviolet (UV)-resistant microorganisms; however, the molecular mechanisms of this resistance are almost unknown. By means of in vivo NMR spectroscopy, we determined the metabolic profile of living F. salina cells exposed to visible light and to polychromatic UV-B + UV-A + Vis radiation for several different exposure times. We used unsupervised pattern-recognition analysis to compare these profiles and discovered some metabolites whose concentration changed specifically upon UV exposure and in a dose-dependent manner. This variation was interpreted in terms of a two-phase cell reaction involving at least two different pathways: an early response consisting of degradation processes, followed by a late response activating osmoprotection mechanisms. The first step alters the concentration of formate, acetate, and saturated fatty-acid metabolites, whereas the osmoprotection modifies the activity of betaine moieties and other functionally related metabolites. In the latter pathway, alanine, proline, and sugars suggest a possible incipient protein synthesis as defense and/or degeneration mechanisms. We conclude that NMR spectroscopy on in vivo cells is an optimal approach for investigating the effect of UV-induced stress on the whole metabolome of F. salina because it minimizes the invasiveness of the measurement.
Assuntos
Cilióforos/imunologia , Cilióforos/metabolismo , Metaboloma/efeitos da radiação , Raios Ultravioleta , Cilióforos/efeitos da radiação , Espectroscopia de Ressonância Magnética , Análise de Componente Principal , Espectrofotometria UltravioletaRESUMO
We tested whether mixotrophic ciliates are more resistant to solar ultraviolet radiation (UVR) than heterotrophic ones because symbiotic algae can provide self-shading by cell matter absorption and eventually by direct UV screening from mycosporine-like amino acids (MAAs). Sensitivity of a natural assemblage to solar radiation was tested in experiments in the original lake and in a more UV transparent alpine lake after transplantation of the ciliates. In both lakes, the assemblage was exposed either to full sunlight, to photosynthetically active radiation only, or kept in the dark. In each lake, exposure was for 5 h at the surface and at the depth corresponding to the 10% attenuation depth at 320 nm. Overall, when the assemblage was exposed to surface UVR, only one out of four dominant mixotrophic ciliates, Vorticella chlorellata, was more resistant than heterotrophic species. The higher UV resistance in V. chlorellata was related to the presence of MAAs and the high percentage of ciliate volume occupied by algal symbionts. Our results indicate that effects of UVR were species-specific and depended on efficient screening of these wavelengths, but also on the depth preference of the ciliates and thus, on their previous exposure history to UVR.
Assuntos
Cilióforos/efeitos da radiação , Água Doce/parasitologia , Raios Ultravioleta , Aminoácidos/isolamento & purificação , Sobrevivência Celular/efeitos da radiação , Cilióforos/química , Cilióforos/microbiologia , SimbioseRESUMO
The coloured ciliate Blepharisma japonicum changes swimming velocity (positive photokinesis) and elongates its body in response to a prolonged illumination. We have recently proposed that alterations in the phosphorylation level of the ciliate phosducin (Pdc) may be involved in light-induced cell elongation, which in turn affects the interaction of ßγ-dimer of G-proteins (Gßγ) with ß-tubulin and subsequent cytoskeletal remodelling. The cellular mechanism that governs the photokinetic effect in this ciliate has not been elucidated. In the present study, we utilise real-time PCR to demonstrate that the levels of ciliate Pdc mRNA are significantly reduced in Pdc-RNAi-treated cells compared to cells fed with bacteria carrying the empty vector (control cells). Using western immunoblotting, we confirmed that these cells treated with Pdc-RNAi expressed a substantially lower level of the Pdc protein. The assay also revealed that in ciliates treated with Pdc-RNAi and exposed to light, the cytosolic level of Gß (~36 kDa) was reduced, whereas the level of Gß localized to the membrane (~32 kDa) was increased compared to control cells. In addition, behavioural analysis of the cells indicated a substantial reduction of photokinesis. The findings in this study provide additional characterization of the functional properties of the ciliate Pdc protein and we discuss a likely role for this phosphoprotein in the photokinetic phenomenon of the ciliate protist Blepharisma.
Assuntos
Cilióforos/fisiologia , Proteínas do Olho/antagonistas & inibidores , Reguladores de Proteínas de Ligação ao GTP/antagonistas & inibidores , Fosfoproteínas/antagonistas & inibidores , Cilióforos/citologia , Cilióforos/efeitos da radiação , Proteínas do Olho/genética , Proteínas do Olho/metabolismo , Reguladores de Proteínas de Ligação ao GTP/genética , Reguladores de Proteínas de Ligação ao GTP/metabolismo , Subunidades beta da Proteína de Ligação ao GTP/análise , Subunidades beta da Proteína de Ligação ao GTP/metabolismo , Subunidades gama da Proteína de Ligação ao GTP/análise , Subunidades gama da Proteína de Ligação ao GTP/metabolismo , Cinética , Luz , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Fosforilação , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Tubulina (Proteína)/metabolismoRESUMO
Radiofrequency exposure at the mobile connection frequency (1 GHz) at different energy flow densities, 5 µW/cm(2)(2-fold below the maximum permissible level) and 50 µW/cm(2)(5-fold surpassing this level), caused a reduction of motor activity in unicellular hydrobionts Spirostomum ambiguum Ehrbg infusoria. In all cases, the effect was similar by the intensity and developed in a jump-wise manner after exposure of a certain duration, after which did not increase with prolongation of the exposure. The duration of radiofrequency exposure safe for the object varied significantly: 8-9 h and 10 min at 5 and 50 µW, respectively. These innovation data on harmful biological effects of very low radiofrequency exposure (5 µW/cm(2)), the threshold form of biological reaction, presence of "safe" periods of exposure, and the data demonstrating a clear-cut relationship between these periods and energy flow density are interesting from theoretical viewpoint and in connection with the problem of evaluating permissible levels of radiofrequency exposure of biological objects.
Assuntos
Cilióforos/efeitos da radiação , Ondas de Rádio , Cilióforos/metabolismo , Relação Dose-Resposta à RadiaçãoRESUMO
Blepharisma japonicum ciliates display reversible cell elongation in response to lasting bright illumination. This light-induced phenomenon has been ascribed to the active sliding of the cortical microtubules of the ciliate. The detailed intracellular signaling pathway that activates the microtubule network in response to light, resulting in cell elongation, is unknown. We have previously reported that light stimulation initiates sequential molecular events consisting of a decrease in the phosphorylation of ciliate Pdc, followed by increased binding of Pdc to membrane-localised Gbetagamma and the subsequent translocation of the Pdc-Gbetagamma complex to the cytoplasm. In this study, we used selected agents known to influence protein phosphorylation to test whether alterations in Pdc phosphorylation levels by light affect ciliate shape. Behavioural analysis indicated that cell treatment with okadaic acid, an inhibitor of protein phosphatase activity, heavily abolished the effect of light on cell elongation, whereas the presence of H-89, a specific inhibitor of cAMP-dependent protein kinase (PKA) activity, had no appreciable effect on the cell length. Phosphorylation assays showed that cell incubation with H-89 mimicked light by promoting Pdc dephosphorylation and its colocalization with Gbetagamma. However, as demonstrated by FRET-AP, Pdc-Gbetagamma complex formation and changes in the length of the cell did not occur under the same conditions. Moreover, fluorescence microscopy showed localization of Gbetagamma and beta-tubulin in the same cell compartment and demonstrated that a direct interaction between these proteins occurs in cells adapted to darkness or exposed to prolonged illumination (> or = 10 min). In contrast, an opposite effect, i.e. a transient decrease in the interaction between Gbetagamma and beta-tubulin and distinct Pdc dephosphorylation, was observed in cells illuminated for short time. Under these conditions, Pdc preferentially occupies the cell submembrane region and interacts with Gbetagamma. In cells illuminated for a longer time (> or = 10 min) and despite the constant light intensity, Pdc was progressively rephosphorylated and then dissociated from Gbetagamma, relocalizing within the cell cytoplasm. The results obtained in this study suggest that alterations in Pdc phosphorylation may be involved in light-induced elongation of the Blepharisma cell body, which affects the interaction of Gbetagamma with beta-tubulin and cell cytoskeleton remodelling.
Assuntos
Cilióforos/efeitos da radiação , Subunidades beta da Proteína de Ligação ao GTP/metabolismo , Subunidades gama da Proteína de Ligação ao GTP/metabolismo , Luz , Tubulina (Proteína)/metabolismo , Cilióforos/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/antagonistas & inibidores , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Proteínas do Olho/metabolismo , Transferência Ressonante de Energia de Fluorescência , Reguladores de Proteínas de Ligação ao GTP/metabolismo , Subunidades beta da Proteína de Ligação ao GTP/análise , Subunidades gama da Proteína de Ligação ao GTP/análise , Isoquinolinas/farmacologia , Ácido Okadáico/farmacologia , Fosfoproteínas Fosfatases/antagonistas & inibidores , Fosfoproteínas Fosfatases/metabolismo , Fosfoproteínas/metabolismo , Fosforilação , Sulfonamidas/farmacologia , Fatores de Tempo , Tubulina (Proteína)/análiseRESUMO
Blepharismins are photodynamic hypericin-like dianthrones produced as a variable pigment blend in Blepharisma ciliates and mostly studied in the Afro-Asiatic Blepharisma japonicum. The present work describes the bioactivity of pigments from the Brazilian Blepharisma sinuosum. Comparative analyses showed that the pigments from both species can trigger photo-induced modifications in phospholipids, but different redox properties and biological activities were assigned for each pigment blend. Stronger activities were detected for B. sinuosum pigments, with the lethal concentration LC50 10 × lower than B. japonicum pigments in light-irradiated tests against Bacillus cereus and less than half for treatments on the human HeLa tumor cells. HPLC showed B. sinuosum producing a simpler pigment blend, mostly with the blepharismin-C (~ 70%) and blepharismin-E (~ 30%) types. Each blepharismin engaged a specific dose-response profile on sensitive cells. The blepharismin-B and blepharismin-C were the most toxic pigments, showing LC50 ~ 2.5-3.0 µm and ~ 100 µm on B. cereus and HeLa cells, respectively, after illumination. Similarity clustering analysis compiling the bioactivity data revealed two groups of blepharismins: the most active, B and C, and the less active, A, D and E. The B. sinuosum pigment blend includes one representative of each clade. Functional and medical implications are discussed.
Assuntos
Cilióforos/efeitos da radiação , Fotoquimioterapia , Cilióforos/classificação , Células HeLa , Humanos , Dose Letal Mediana , Especificidade da EspécieRESUMO
The unicellular eukaryote, Blepharisma japonicum, is a light-sensitive ciliated protozoa. It possesses a photoreceptor pigment called blepharismin that plays critical roles in defensive behavior against predators and step-up photophobic response. In addition, the pigment generates reactive oxygen species such as singlet oxygen and hydroxyl radicals which contribute to photodynamic action. Previous studies reported that intense light (>300W m(-2)) induced rapid photodynamic killing (necrosis) characterized by cell swelling and plasma efflux, while moderate light (3-30W m(-2)) only induced pigment extrusion and photooxidation. We have found that moderate light (5W m(-2)) induced apoptosis-like cell death. Microscopically it was found that >3h of moderate light irradiation induced macronuclear condensation and plasma efflux without cell swelling. Single cell gel electrophoresis assay showed that DNA fragmentation occurred between 1 and 3h of irradiation, and the condensed macronuclei contained quite fragmented DNA. Macronuclear DNA extracted from light-irradiated cells contained DNA fragments of 180-200 and 360-400bp, which were seen as apoptosis ladders.
Assuntos
Apoptose , Cilióforos/efeitos da radiação , Luz , Animais , Cilióforos/fisiologia , Ensaio Cometa , Fragmentação do DNA/efeitos da radiação , Macronúcleo/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Fatores de TempoRESUMO
Electromagnetic radiation at the mobile connection frequency (1 GHz) at maximum energy flow density (10 microW/cm(2)) permitted in Russia causes serious functional disorders in the studied unicellular hydrobionts infusoria Spirostomum ambiguum: reduction of their spontaneous motor activity. The form of biological reaction is uncommon: the effect is threshold, overall, and does not depend on the duration of microwave exposure.
Assuntos
Cilióforos/efeitos da radiação , Campos Eletromagnéticos/efeitos adversos , Micro-Ondas/efeitos adversos , Atividade Motora/efeitos da radiação , Animais , Fatores de TempoRESUMO
Phytoplankton and associated microbial communities provide organic carbon to oceanic food webs and drive ecosystem dynamics. However, capturing those dynamics is challenging. Here, an in situ, semi-Lagrangian, robotic sampler profiled pelagic microbes at 4 h intervals over ~2.6 days in North Pacific high-nutrient, low-chlorophyll waters. We report on the community structure and transcriptional dynamics of microbes in an operationally large size class (>5 µm) predominantly populated by dinoflagellates, ciliates, haptophytes, pelagophytes, diatoms, cyanobacteria (chiefly Synechococcus), prasinophytes (chiefly Ostreococcus), fungi, archaea, and proteobacteria. Apart from fungi and archaea, all groups exhibited 24-h periodicity in some transcripts, but larger portions of the transcriptome oscillated in phototrophs. Periodic photosynthesis-related transcripts exhibited a temporal cascade across the morning hours, conserved across diverse phototrophic lineages. Pronounced silica:nitrate drawdown, a high flavodoxin to ferredoxin transcript ratio, and elevated expression of other Fe-stress markers indicated Fe-limitation. Fe-stress markers peaked during a photoperiodically adaptive time window that could modulate phytoplankton response to seasonal Fe-limitation. Remarkably, we observed viruses that infect the majority of abundant taxa, often with total transcriptional activity synchronized with putative hosts. Taken together, these data reveal a microbial plankton community that is shaped by recycled production and tightly controlled by Fe-limitation and viral activity.
Assuntos
Ferro/metabolismo , Microbiota , Plâncton/genética , Plâncton/virologia , California , Cilióforos/genética , Cilióforos/metabolismo , Cilióforos/efeitos da radiação , Cilióforos/virologia , Diatomáceas/genética , Diatomáceas/metabolismo , Diatomáceas/efeitos da radiação , Diatomáceas/virologia , Dinoflagellida/genética , Dinoflagellida/metabolismo , Dinoflagellida/efeitos da radiação , Dinoflagellida/virologia , Cadeia Alimentar , Haptófitas/genética , Haptófitas/metabolismo , Haptófitas/efeitos da radiação , Haptófitas/virologia , Oceanos e Mares , Fotossíntese , Fitoplâncton/genética , Fitoplâncton/metabolismo , Fitoplâncton/efeitos da radiação , Fitoplâncton/virologia , Plâncton/metabolismo , Plâncton/efeitos da radiação , Transcrição Gênica , Fenômenos Fisiológicos Virais , Vírus/genéticaRESUMO
In the light of the predicted global climate change, it is essential that the status and diversity of polar microbial communities is described and understood. In the present study, molecular tools were used to investigate the marine eukaryotic communities of Prydz Bay, Eastern Antarctica, from November 2002 to January 2003. Additionally, we conducted four series of minicosm experiments, where natural Prydz Bay communities were incubated under six different irradiation regimes, in order to investigate the effects of natural UV radiation on marine microbial eukaryotes. Denaturing gradient gel electrophoresis (DGGE) and 18S rRNA gene sequencing revealed a eukaryotic Shannon diversity index averaging 2.26 and 2.12, respectively. Phylogenetic analysis of 472 sequenced clones revealed 47 phylotypes, belonging to the Dinophyceae, Stramenopiles, Choanoflagellidae, Ciliophora, Cercozoa and Metazoa. Throughout the studied period, three communities were distinguished: a postwinter/early spring community comprising dinoflagellates, ciliates, cercozoans, stramenopiles, viridiplantae, haptophytes and metazoans; a dinoflagellate-dominated community; and a diatom-dominated community that developed after sea ice breakup. DGGE analysis showed that size fraction and time had a strong shaping effect on the community composition; however, a significant contribution of natural UV irradiance towards microeukaryotic community composition could not be detected. Overall, dinoflagellates dominated our samples and their diversity suggests that they fulfill an important role in Antarctic coastal marine ecosystems preceding ice breakup as well as between phytoplankton bloom events.
Assuntos
Ecossistema , Células Eucarióticas , Biologia Marinha , Raios Ultravioleta , Animais , Regiões Antárticas , Cilióforos/classificação , Cilióforos/genética , Cilióforos/fisiologia , Cilióforos/efeitos da radiação , DNA Ribossômico/análise , Dinoflagellida/classificação , Dinoflagellida/genética , Dinoflagellida/fisiologia , Dinoflagellida/efeitos da radiação , Células Eucarióticas/classificação , Células Eucarióticas/fisiologia , Células Eucarióticas/efeitos da radiação , Dados de Sequência Molecular , RNA Ribossômico 18S/genética , Análise de Sequência de DNARESUMO
Recently we reported a light-induced cDNA encoding glutathione S-transferase (GST) from the ciliated protozoa Blepharisma japonicum, which possessed photosensitive pigments. In this study, a novel cDNA encoding GST was further isolated, and the two GSTs (BjGST1 and BjGST2) showed high sequence identity of 86%. Phylogenetic trees indicated that the BjGSTs were distantly related to known classes of GSTs, and they could form a protozoa-specific class. The recombinant proteins also existed as homo- or heterodimers that exhibited different enzyme activities, appreciating the functional differentiation. Furthermore, the transcription levels of BjGST genes were coordinately regulated in response to light stimulation. In addition, the genomic structure analysis revealed that the two genes were tandemly arranged through an approximately 500-bp spacer region of unusual DNA structure containing cis-acting elements related to oxidative stress response. These results demonstrate that the two BjGSTs are expressed simultaneously and act cooperatively against photooxidative stress.
Assuntos
Cilióforos/enzimologia , Cilióforos/genética , Regulação Enzimológica da Expressão Gênica/efeitos da radiação , Glutationa Transferase/genética , Proteínas de Protozoários/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Sítios de Ligação , Cilióforos/efeitos da radiação , Eucariotos/classificação , Eucariotos/genética , Genoma de Protozoário , Glutationa Transferase/química , Glutationa Transferase/metabolismo , Luz , Dados de Sequência Molecular , Filogenia , Proteínas de Protozoários/química , Proteínas de Protozoários/metabolismo , Alinhamento de Sequência , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Gênica/efeitos da radiaçãoRESUMO
The spontaneous motional activity of paramecium Spirostomum ambiguum Ehrbg. has high sensitivity to the gamma-irradiation. The increase of this parameter has been observed just after irradiation in the 0.1 Gy. It is approximately on the similar level (about 35% below control) in a broad variety of doze (to 850 Gy inclusive). After that the dozes 1000-1500 Gy has been obtained, the effect became stronger. The present result has been interesting in the question of the behavior's reaction unicellular using in the indication of the radioactivity contamination of the aquatic aria. And also it is actual in the common problem of the irradiation activity on the biota.
Assuntos
Movimento Celular/efeitos da radiação , Cilióforos/efeitos da radiação , Raios gama/efeitos adversos , Monitoramento de Radiação/métodos , Poluentes Radioativos da Água/toxicidade , Animais , Bioensaio/métodos , Cilióforos/fisiologia , Relação Dose-Resposta à RadiaçãoRESUMO
Blepharisma japonicum and Stentor coeruleus are related ciliates, conspicuous by their photosensitivity. They are capable of avoiding illuminated areas in the surrounding medium, gathering exclusively in most shaded places (photodispersal). Such behaviour results mainly from motile photophobic response occurring in ciliates. This light-avoiding response is observed during a relatively rapid increase in illumination intensity (light stimulus) and consists of cessation of cell movement, a period of backward movement (ciliary reversal), followed by a forward swimming, usually in a new direction. The photosensitivity of ciliates is ascribed to their photoreceptor system, composed of pigment granules, containing the endogenous photoreceptor -- blepharismin in Blepharisma japonicum, and stentorin in Stentor coeruleus. A light stimulus, applied to both ciliates activates specific stimulus transduction processes leading to the electrical changes at the plasma membrane, correlated with a ciliary reversal during photophobic response. These data indicate that both ciliates Blepharisma japonicum and Stentor coeruleus, the lower eukaryotes, are capable of transducing the perceived light stimuli in a manner taking place in some photoreceptor cells of higher eukaryotes. Similarities and differences concerning particular stages of light transduction in eukaryotes at different evolutional levels are discussed in this article.