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1.
PLoS One ; 14(6): e0218238, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31242214

RESUMEN

Ocean acidification (O.A.) influences the ecology of oceans and it may impact plant-animal interactions at various levels. Seagrass meadows located at acidified vents in the Bay of Naples (Italy) are considered an open window to forecast the effects of global-changes on aquatic communities. Epiphytic diatoms of the genus Cocconeis are abundant in seagrass meadows, including acidified environments, where they play key ecological roles. A still-unknown apoptogenic compound produced by Cocconeis triggers the suicide of the androgenic gland of Hippolyte inermis Leach 1816, a protandric hermaphroditic shrimp distributed in P. oceanica meadows located both at normal pH and in acidified vents. Feeding on Cocconeis sp. was proven important for the stability of the shrimp's natural populations. Since O.A. affects the physiology of diatoms, we investigated if, in future scenarios of O.A., Cocconeis scutellum parva will still produce an effect on shrimp's physiology. Cell densities of Cocconeis scutellum parva cultivated in custom-designed photobioreactors at two pH conditions (pH 7.7 and 8.2) were compared. In addition, we determined the effects of the ingestion of diatoms on the process of sex reversal of H. inermis and we calculated the % female on the total of mature individuals-1 (F/mat). We observed significant differences in cell densities of C. scutellum parva at the two pH conditions. In fact, the highest cell densities (148,808 ±13,935 cells. mm-2) was obtained at day 13 (pH 7.7) and it is higher than the highest cell densities (38,066 (±4,166) cells. mm-2, day 13) produced at pH 8.2. Diatoms cultured at acidified conditions changed their metabolism. In fact, diatoms grown in acidified conditions produced in H. inermis a proportion of females (F/mat 36.3 ±5.9%) significantly lower than diatoms produced at normal pH (68.5 ±2.8), and it was not significantly different from that elicited by negative controls (31.7 ±5.6%).


Asunto(s)
Ácidos/química , Crustáceos/fisiología , Océanos y Mares , Estramenopilos/fisiología , Animales , Femenino , Masculino , Fotobiorreactores , Agua de Mar
2.
Protist ; 170(2): 209-232, 2019 04.
Artículo en Inglés | MEDLINE | ID: mdl-31100647

RESUMEN

Strain HS-399 was isolated from a mangrove swamp in Biscayne Bay (Florida, USA) and selected for its capacity to accumulate lipids (84.0±1.0% DW), particularly docosahexaenoic acid (DHA; 22:6 n-3) (28.3±0.1% DW). Molecular phylogenetic analysis demonstrated that the new organism belonged to the genus Aurantiochytrium, and when the whole nuclear genome was blasted against the type species (and only described species), A. limacinum SR21, there was a 5.38% difference at the protein level. We described our new organism as Aurantiochytrium acetophilum sp. nov. (Thraustochytriaceae, Thraustochytriales) using light microscopy, electron microscopy, substrate assimilation, biochemical composition and nuclear genomic data. We found some characteristics of biotechnological relevance that were not previously described in this family. First, strain HS-399 of A. acetophilum was extremely tolerant to acetate toxicity, and it used this substrate as a sole carbon source. Second, we observed putative gametes that fused together to form a zygote. Zygote fate and the life stage with meiosis were not determined; however, we found several meiosis genes in the genome, further supporting the possibility of breeding for these industrially relevant organisms.


Asunto(s)
Genoma de Protozoos , Filogenia , Estramenopilos/clasificación , Estramenopilos/genética , Reproducción , Especificidad de la Especie , Estramenopilos/fisiología
3.
Photosynth Res ; 140(3): 337-354, 2019 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-30701484

RESUMEN

This work highlights spectroscopic investigations on a new representative of photosynthetic antenna complexes in the LHC family, a putative violaxanthin/vaucheriaxanthin chlorophyll a (VCP) antenna complex from a freshwater Eustigmatophyte alga FP5. A representative VCP-like complex, named as VCP-B3 was studied with both static and time-resolved spectroscopies with the aim of obtaining a deeper understanding of excitation energy migration within the pigment array of the complex. Compared to other VCP representatives, the absorption spectrum of the VCP-B3 is strongly altered in the range of the chlorophyll a Qy band, and is substantially red-shifted with the longest wavelength absorption band at 707 nm at 77 K. VCP-B3 shows a moderate xanthophyll-to-chlorophyll a efficiency of excitation energy transfer in the 50-60% range, 20-30% lower from comparable VCP complexes from other organisms. Transient absorption studies accompanied by detailed data fitting and simulations support the idea that the xanthophylls that occupy the central part of the complex, complementary to luteins in the LHCII, are violaxanthins. Target analysis suggests that the primary route of xanthophyll-to-chlorophyll a energy transfer occurs via the xanthophyll S1 state.


Asunto(s)
Transferencia de Energía , Complejos de Proteína Captadores de Luz/metabolismo , Estramenopilos/fisiología , Clorofila A/metabolismo , Luz , Fotosíntesis , Estramenopilos/efectos de la radiación , Tilacoides/metabolismo , Xantófilas/metabolismo
4.
PLoS One ; 14(1): e0209920, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30625205

RESUMEN

Heterokont algae are significant contributors to marine primary productivity. These algae have a photosynthetic machinery that shares many common features with that of Viridiplantae (green algae and land plants). Here we demonstrate, however, that the photosynthetic machinery of heterokont algae responds to light fundamentally differently than that of Viridiplantae. While exposure to high light leads to electron accumulation within the photosynthetic electron transport chain in Viridiplantae, this is not the case in heterokont algae. We use this insight to manipulate the photosynthetic electron transport chain and demonstrate that heterokont algae can dynamically distribute excitation energy between the two types of photosystems. We suggest that the reported electron transport and excitation distribution features are adaptations to the marine light environment.


Asunto(s)
Transporte de Electrón/fisiología , Fotosíntesis/fisiología , Oxidación-Reducción , Estramenopilos/metabolismo , Estramenopilos/fisiología , Viridiplantae/metabolismo , Viridiplantae/fisiología
5.
Microb Ecol ; 78(1): 1-5, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30448922

RESUMEN

In the marine environment, the abundance of Bacteria and Archaea is either controlled bottom-up via nutrient availability or top-down via grazing. Heterotrophic nanoflagellates (HNF) are mainly responsible for prokaryotic grazing losses besides viral lysis. However, the grazing specificity of HNF on specific bacterial and archaeal taxa is under debate. Bacteria and Archaea might have different nutritive values and surface properties affecting the growth rates of HNF. In this study, we offered different bacterial and archaeal strains with different morphologic and physiologic characteristics to Cafeteria roenbergensis, one of the most abundant and ubiquitous species of HNF in the ocean. Two Nitrosopumilus maritimus-related strains isolated from the northern Adriatic Sea (Nitrosopumilus adriaticus, Nitrosopumilus piranensis), two Nitrosococcus strains, and two fast growing marine Bacteria (Pseudoalteromonas sp. and Marinobacter sp.) were fed to Cafeteria cultures. Cafeteria roenbergensis exhibited high growth rates when feeding on Pseudoalteromonas sp., Marinobacter sp., and Nitrosopumilus adriaticus, while the addition of the other strains resulted in minimal growth. Taken together, our data suggest that the differences in growth of Cafeteria roenbergensis associated to grazing on different thaumarchaeal and bacterial strains are likely due to the subtle metabolic, cell size, and physiological differences between different bacterial and thaumarchaeal taxa. Moreover, Nitrosopumilus adriaticus experienced a similar grazing pressure by Cafeteria roenbergensis as compared to the other strains, suggesting that other HNF may also prey on Archaea which might have important consequences on the global biogeochemical cycles.


Asunto(s)
Archaea/aislamiento & purificación , Bacterias/aislamiento & purificación , Estramenopilos/fisiología , Archaea/clasificación , Archaea/genética , Bacterias/clasificación , Bacterias/genética , Conducta Alimentaria , Cadena Alimentaria , Procesos Heterotróficos , Agua de Mar/microbiología , Agua de Mar/parasitología , Estramenopilos/clasificación , Estramenopilos/crecimiento & desarrollo
6.
Biochim Biophys Acta Bioenerg ; 1860(2): 111-120, 2019 02 01.
Artículo en Inglés | MEDLINE | ID: mdl-30414929

RESUMEN

Photosynthetic eukaryotes whose cells harbor plastids originating from secondary endosymbiosis of a red alga include species of major ecological and economic importance. Since utilization of solar energy relies on the efficient light-harvesting, one of the critical factors for the success of the red lineage in a range of environments is to be found in the adaptability of the light-harvesting machinery, formed by the proteins of the light-harvesting complex (LHC) family. A number of species are known to employ mainly a unique class of LHC containing red-shifted chlorophyll a (Chl a) forms absorbing above 690 nm. This appears to be an adaptation to shaded habitats. Here we present a detailed investigation of excitation energy flow in the red-shifted light-harvesting antenna of eustigmatophyte Trachydiscus minutus using time-resolved fluorescence and ultrafast transient absorption measurements. The main carotenoid in the complex is violaxanthin, hence this LHC is labeled the red-violaxanthin-Chl a protein, rVCP. Both the carotenoid-to-Chl a energy transfer and excitation dynamics within the Chl a manifold were studied and compared to the related antenna complex, VCP, that lacks the red-Chl a. Two spectrally defined carotenoid pools were identified in the red antenna, contributing to energy transfer to Chl a, mostly via S2 and hot S1 states. Also, Chl a triplet quenching by carotenoids is documented. Two separate pools of red-shifted Chl a were resolved, one is likely formed by excitonically coupled Chl a molecules. The structural implications of these observations are discussed.


Asunto(s)
Clorofila A , Transferencia de Energía/fisiología , Complejos de Proteína Captadores de Luz/química , Estramenopilos/fisiología , Chlorophyta/fisiología , Plastidios , Rhodophyta/fisiología , Espectrometría de Fluorescencia/métodos , Xantófilas
7.
Protist ; 170(1): 38-51, 2019 02.
Artículo en Inglés | MEDLINE | ID: mdl-30576874

RESUMEN

Heterosigma akashiwo is a raphidophyte known for forming ichthyotoxic blooms. In order to predict the potential impacts of rising CO2 on H. akashiwo it is necessary to understand the factors influencing growth rates over a range of CO2 concentrations. Here we examined the physiology and gene expression response of H. akashiwo to concentrations from 200 to 1000ppm CO2. Growth rate data were combined from this and previous studies and fit with a CO2 limitation-inhibition model that revealed an apparent growth optimum around 600-800ppm CO2. Physiological changes included a significant increase in C:N ratio at ∼800ppm CO2 and a significant decrease in hydrogen peroxide concentration at ∼1000ppm. Whole transcriptome sequencing of H. akashiwo revealed sharp distinctions in metabolic pathway gene expression between ∼600 and ∼800ppm CO2. Hierarchical clustering by co-expression identified groups of genes with significant correlations to CO2 and growth rate. Genes with significant differential expression with CO2 included carbon concentrating mechanism genes such as beta-carbonic anhydrases and a bicarbonate transporter, which may underpin shifts in physiology. Genes involved in cell motility were significantly changed by both elevated CO2 and growth rate, suggesting that future ocean conditions could modify swimming behavior in this species.


Asunto(s)
Dióxido de Carbono/análisis , Expresión Génica , Estramenopilos/fisiología , Estramenopilos/genética
8.
Mar Drugs ; 16(11)2018 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-30388843

RESUMEN

In humans, dietary polyunsaturated fatty acids (PUFAs) are involved in therapeutic processes such as prevention and treatment of cardiovascular diseases, neuropsychiatric disorders, and dementia. We examined the physiology, PUFA accumulation and glycerol lipid biosynthesis in the marine microalga Nannochloropsis salina in response to constant suboptimal temperature (<20 °C). As expected, N. salina exhibited significantly reduced growth rate and photosynthetic activity compared to optimal cultivation temperature. Total fatty acid contents were not significantly elevated at reduced temperatures. Cultures grown at 5 °C had the highest quantity of eicosapentanoic acid (EPA) (C20:5n3) and the lowest growth rate. Additionally, we monitored broadband lipid composition to model the occurrence of metabolic alteration and remodeling for various lipid pools. We focused on triacylglycerol (TAG) with elevated PUFA content. TAGs with EPA at all three acyl positions were higher at a cultivation temperature of 15 °C. Furthermore, monogalactosyldiacylglycerol and digalactosyldiacylglycerol, which are polar lipids associated with chloroplast membranes, decreased with reduced cultivation temperatures. Moreover, gene expression analysis of key genes involved in Kennedy pathway for de novo TAG biosynthesis revealed bimodal variations in transcript level amongst the temperature treatments. Collectively, these results show that Nannochloropsis salina is a promising source of PUFA containing lipids.


Asunto(s)
Aclimatación/fisiología , Vías Biosintéticas/genética , Microalgas/fisiología , Estramenopilos/fisiología , Triglicéridos/biosíntesis , Frío , Ácidos Grasos Insaturados/química , Ácidos Grasos Insaturados/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica/fisiología , Metabolismo de los Lípidos/fisiología , Metaboloma/fisiología , Aguas Salinas , Triglicéridos/química
9.
Mar Drugs ; 16(9)2018 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-30200435

RESUMEN

Aurantiochytrium sp. PKU#SW7 is a thraustochytrid strain that was found to exhibit high potential for docosahexaenoic acid (DHA, C22:6n-3) production. In this work, the transcriptome of Aurantiochytrium sp. PKU#SW7 was analyzed for the study of genes involved in basic metabolic functions and especially in the mechanisms of DHA biosynthesis. Sequence annotation and functional analysis revealed that the strain contains components of fatty acid synthesis (FAS) and polyketide synthase (PKS) pathways. Fatty acid desaturases and elongases were identified as components of FAS pathway, whilst key components of PKS pathway were also found in the cDNA library. The relative contribution of the two pathways to the synthesis of DHA was unknown, as both pathways appeared to be lacking full complement of genes for standalone synthesis of DHA. Further analysis of two putative genes encoding the very-long-chain (3R)-3-hydroxyacyl-CoA dehydratase and dehydrase/isomerase involved in FAS and PKS pathways, respectively, revealed that under various salinity conditions, their relative expression levels changed corresponding to the variation of DHA content in Aurantiochytrium sp. Independent knock outs of these genes in Aurantiochytrium sp. resulted in poor cell growth, probably due to little or no intracellular DHA accumulation. Hence, it can be speculated that both genes are engaged in DHA biosynthesis and DHA in Aurantiochytrium sp. could be produced by jointed actions of both FAS and PKS systems.


Asunto(s)
Organismos Acuáticos/fisiología , Vías Biosintéticas/genética , Proliferación Celular , Ácidos Docosahexaenoicos/biosíntesis , Estramenopilos/fisiología , Acetiltransferasas/genética , Acetiltransferasas/metabolismo , Ácido Graso Desaturasas/genética , Ácido Graso Desaturasas/metabolismo , Perfilación de la Expresión Génica , Técnicas de Inactivación de Genes , Sintasas Poliquetidas/genética , Sintasas Poliquetidas/metabolismo
10.
Protist ; 169(5): 727-743, 2018 11.
Artículo en Inglés | MEDLINE | ID: mdl-30118923

RESUMEN

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.


Asunto(s)
Citoplasma/metabolismo , Estramenopilos/fisiología , Adhesión Celular , Conducta Alimentaria , Microscopía Electrónica de Transmisión , Nutrientes/metabolismo , Estramenopilos/ultraestructura
11.
Dis Aquat Organ ; 130(1): 51-63, 2018 08 28.
Artículo en Inglés | MEDLINE | ID: mdl-30154272

RESUMEN

Eelgrass wasting disease, caused by the marine pathogen Labyrinthula zosterae, has the potential to devastate important eelgrass habitats worldwide. Although this host-pathogen interaction may increase under certain environmental conditions, little is known about how disease severity is impacted by multiple components of a changing environment. In this study, we investigated the effects of variation in 3 different L. zosterae isolates, pathogen dosage, temperature, and light on severity of infections. Severity of lesions on eelgrass varied among the 3 different isolates inoculated in laboratory trials. Our methods to control dosage of inoculum showed that disease severity increased with pathogen dosage from 104 to 106 cells ml-1. In a dosage-controlled light and temperature 2-way factorial experiment consisting of 2 light regimes (diel light cycle and complete darkness) and 2 temperatures (11 and 18°C), L. zosterae cell growth rate in vitro was higher at the warmer temperature. In a companion experiment that tested the effects of light and temperature in in vivo inoculations, disease severity was higher in dark treatments and temperature was marginally significant. We suggest that the much greater impact of light in the in vivo inoculation experiment indicates an important role for plant physiology and the need for photosynthesis in slowing severity of infections. Our work with controlled inoculation of distinct L. zosterae isolates shows that pathogen isolate, increasing dosage of inoculum, increasing temperature, and diminishing light increase disease severity, suggesting L. zosterae will cause increased damage to eelgrass beds with changing environmental conditions.


Asunto(s)
Estramenopilos/fisiología , Zosteraceae/microbiología , Endófitos/fisiología , Enfermedades de las Plantas/microbiología , Temperatura Ambiental , Virulencia
12.
Dis Aquat Organ ; 130(1): 65-70, 2018 08 28.
Artículo en Inglés | MEDLINE | ID: mdl-30154273

RESUMEN

Marine heterotrophic protists of the Labyrinthulomycota are of interest for their biotechnological (e.g. thraustochytrid production of lipids) and ecological (e.g. wasting disease and rapid blight by pathogens of the genus Labyrinthula) applications; culture-based laboratory studies are a central technique of this research. However, maintaining such microorganism cultures can be labour- and cost-intensive, with a high risk of culture contamination and die-off over time. Deep-freeze storage, or cryopreservation, can be used to maintain culture back-ups, as well as to preserve the genetic and phenotypic properties of the microorganisms; however, this method has not been tested for the ubiquitous marine protists Labyrinthula spp. In this study, we trialled 12 cryopreservation protocols on 3 Labyrinthula sp. isolates of varying colony morphological traits. After 6 mo at -80°C storage, the DMSO and glycerol protocols were the most effective cryoprotectants compared to methanol (up to 90% success vs. 50% success, respectively). The addition of 30% horse serum to the cryoprotectant solution increased Labyrinthula sp. growth success by 20-30%. We expect that these protocols will provide extra security for culture-based studies, as well as opportunities for long-term research on key Labyrinthula sp. isolates.


Asunto(s)
Criopreservación/métodos , Estramenopilos/fisiología , Animales , Crioprotectores/farmacología , Dimetilsulfóxido , Glicerol , Caballos , Suero , Manejo de Especímenes , Factores de Tiempo
13.
Harmful Algae ; 77: 55-65, 2018 07.
Artículo en Inglés | MEDLINE | ID: mdl-30005802

RESUMEN

Harmful algal blooms (HABs) have affected salmon farms in Chile since the early 1970's, causing massive losses in fish. Two large HABs occurred in 2002 and 2009, during which Alexandrium catenella blooms killed tons of salmon over an extended geographic area in southern Chile. At the beginning of 2016, high and persistent densities of Pseudochattonella cf. verruculosa and A. catenella were detected in the estuarine and marine ecosystems of southern Chile. Mortality for this latter event reached 27 million salmon and trout (i.e. 39,000 tons). Unfortunately, the threshold concentrations of algae that could be harmful to the health of farmed salmon in southern Chile have not yet been quantified. Here, to protect fish farms from HABs, critical concentration levels, i.e. thresholds at which the behavior of farmed Salmo salar is affected by harmful algae were quantified using generalized linear mixed models (GLMM). An extensive database from southern Chile covering the period from 1989 to 2016 was analyzed. The database included salmon behavior, cell abundance of microalgae and oceanographic factors. For both species analyzed, the higher the cell abundance, the greater the probability of detecting anomalous behavior. A threshold of 397 cells/mL was estimated for A. catenella, although it can increase up to ca. >975 cells/mL at a Secchi depth >6 m and up to 874 cells/mL during flood tide. A threshold value <1 cell/mL for Pseudochattonella cf. verruculosa was found to be associated with anomalous salmon behavior, which significantly increased at a water temperature of 11 °C. Evidence for a relationship between fish behavior and mortality is provided.


Asunto(s)
Acuicultura , Dinoflagelados/fisiología , Floraciones de Algas Nocivas/fisiología , Salmón , Estramenopilos/fisiología , Animales , Chile , Modelos Lineales , Dinámica Poblacional
14.
Harmful Algae ; 76: 66-79, 2018 06.
Artículo en Inglés | MEDLINE | ID: mdl-29887206

RESUMEN

The potential for toxic contaminants and nutrient pollution to alter natural cycles of estuarine phytoplankton blooms is well known, yet few studies have examined how these combined stressors affect harmful algal species. Here, a robust testing protocol was developed to enable an ecotoxicological assessment of responses to commonly co-occurring estuarine contaminants by harmful algal bloom species. The population growth and toxicity (as cell density and hemolytic activity, respectively) of a cultured strain of the toxigenic raphidiophycean, Chattonella subsalsa, were assessed in two experiments (duration 10 days and 28 days) across a gradient of atrazine concentrations and N:P ratios simulating nutrient-rich versus nutrient-depleted regimes. The response of this large-celled, slowly growing alga to atrazine × nutrients depended on growth phase; atrazine was most inhibitory during early exponential population growth (day 10), whereas nutrient regime was a more important influence during later phases of growth (day 28). Without atrazine, toxicity toward fish was highest in low-P cultures. At atrazine levels >25 µg L-1, hemolytic activity was highest in low-N cultures, and increased with increasing atrazine concentration in all nutrient-limited cultures. Hemolytic activity varied inversely with atrazine concentration in N,P-replete conditions. Overall, atrazine inhibitory effects on population growth of this C. subsalsa strain depended on the growth phase and the nutrient regime; hemolytic activity was higher and further enhanced by atrazine in low N-P regimes; and atrazine inhibited hemolytic activity in nutrient-replete conditions. The data suggest that, depending on the growth phase and nutrient regime, atrazine can help promote toxic C. subsalsa blooms.


Asunto(s)
Floraciones de Algas Nocivas/fisiología , Fitoplancton/fisiología , Estramenopilos/fisiología , Contaminantes Químicos del Agua/análisis , Animales , Atrazina/análisis , Estuarios , Peces/sangre , Hemólisis , Nitrógeno/análisis , Nutrientes/análisis , Fósforo/análisis , Fitoplancton/crecimiento & desarrollo , Estramenopilos/crecimiento & desarrollo , Factores de Tiempo
15.
Sci Total Environ ; 631-632: 994-1004, 2018 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-29728009

RESUMEN

Heterotrophic marine protists (Thraustochytrids) have received increasingly global attention as a renewable, sustainable and alternative source of biodiesel because of their high ability of saturated fatty acids (SFAs) accumulation. Yet, the influence of extrinsic factors (nutrients and environmental conditions) on thraustochytrid culture and optimal conditions for high SFAs production are poorly described. In the present study, two different thraustochytrid strains, Schizochytrium sp. PKU#Mn4 and Thraustochytriidae sp. PKU#Mn16 were studied for their growth and SFAs production profiles under various conditions (carbon, nitrogen, temperature, pH, KH2PO4, salinity, and agitation speed). Of the culture conditions, substrates (C and N) source and conc., temperature, and agitation speed significantly influenced the cell growth and SFAs production of both strains. Although both the strains were capable of growth and SFAs production in the broad range of culture conditions, their physiological responses to KH2PO4, pH, and salinity were dissimilar. Under their optimal batch culture conditions, peak SFAs productions of 3.3g/L and 2.2g/L with 62% and 49% SFAs contents (relative to total fatty acids) were achieved, respectively. The results of 5-L fed-batch fermentation under optimal conditions showed a nearly 4.5-fold increase in SFAs production (i.e., 7.5g/L) by both strains compared to unoptimized conditions. Of the two strains, the quality of biodiesel produced from the fatty acids of PKU#Mn4 met the biodiesel standard defined by ASTM6751. This study, to the knowledge of the authors, is the first comprehensive report of optimal fermentation conditions demonstrating enhanced SFAs production by strains belonging to two different thraustochytrid genera and provides the basis for large-scale biodiesel production.


Asunto(s)
Biocombustibles , Ácidos Grasos , Estramenopilos/fisiología , Biomasa , Carbono , Ácidos Grasos Omega-3 , Fermentación , Salinidad , Temperatura Ambiental
16.
Mol Biol Evol ; 35(7): 1706-1711, 2018 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-29659974

RESUMEN

Sacoglossan sea slugs offer fascinating systems to study the onset and persistence of algal-plastid symbioses. Elysia chlorotica is particularly noteworthy because it can survive for months, relying solely on energy produced by ingested plastids of the stramenopile alga Vaucheria litorea that are sequestered in cells lining its digestive diverticula. How this animal can maintain the actively photosynthesizing organelles without replenishment of proteins from the lost algal nucleus remains unknown. Here, we used RNA-Seq analysis to test the idea that plastid sequestration leaves a significant signature on host gene expression during E. chlorotica development. Our results support this hypothesis and show that upon exposure to and ingestion of V. litorea plastids, genes involved in microbe-associated molecular patterns and oxidative stress-response mechanisms are significantly up-regulated. Interestingly, our results with E. chlorotica mirror those found with corals that maintain dinoflagellates as intact cells in symbiosomes, suggesting parallels between these animal-algal symbiotic interactions.


Asunto(s)
Moluscos/metabolismo , Moluscos/microbiología , Estramenopilos/fisiología , Simbiosis , Animales , Regulación hacia Abajo , Regulación hacia Arriba
17.
Fish Shellfish Immunol ; 77: 214-221, 2018 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-29609028

RESUMEN

The hard clam (Mercenaria mercenaria) is among the most economically-important marine species along the east coast of the United States, representing the first marine resource in several Northeastern states. The species is rather resilient to infections and the only important disease of hard clams results from an infection caused by Quahog Parasite Unknown (QPX), a protistan parasite that can lead to significant mortality events in wild and aquacultured clam stocks. Though the presence of QPX disease has been documented since the 1960s, little information is available on cellular and molecular interactions between the parasite and the host. This study examined the interactions between the clam immune system and QPX cells. First, the effect of clam plasma on the binding of hemocytes to parasite cells was evaluated. Second, clam plasma proteins that bind QPX cells were identified through proteomic (LC-MS/MS) analyses. Finally, the effect of prior clam exposure to QPX on the abundance of QPX-reactive proteins in the plasma was evaluated. Results showed that plasma factors enhance the attachment of hemocytes to QPX. Among the proteins that specifically bind to QPX cells, several lectins were identified, as well as complement component proteins and proteolytic enzymes. Furthermore, results showed that some of these lectins and complement-related proteins are inducible as their abundance significantly increased following QPX challenge. These results shed light on plasma proteins involved in the recognition and binding of parasite cells and provide molecular targets for future investigations of factors involved in clam resistance to the disease, and ultimately for the selection of resistant clam stocks.


Asunto(s)
Proteínas Sanguíneas/genética , Interacciones Huésped-Parásitos , Mercenaria/inmunología , Estramenopilos/fisiología , Animales , Proteínas Sanguíneas/metabolismo , Mercenaria/parasitología , Proteómica
18.
Bioessays ; 40(4): e1700198, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29512175

RESUMEN

Despite their diversity and ecological importance, many areas of the SAR-Stramenopila, Alveolata, and Rhizaria-clade are poorly understood as the majority (90%) of SAR species lack molecular data and only 5% of species are from well-sampled families. Here, we review and summarize the state of knowledge about the three major clades of SAR, describing the diversity within each clade and identifying synapomorphies when possible. We also assess the "dark area" of SAR: the morphologically described species that are missing molecular data. The majority of molecular data for SAR lineages are characterized from marine samples and vertebrate hosts, highlighting the need for additional research effort in areas such as freshwater and terrestrial habitats and "non-vertebrate" hosts. We also describe the paucity of data on the biogeography of SAR species, and point to opportunities to illuminate diversity in this major eukaryotic clade. See also the video abstract here: https://youtu.be/_VUXqaX19Rw.


Asunto(s)
Alveolados/fisiología , Oscuridad , Rhizaria/fisiología , Estramenopilos/fisiología , Ecología , Ecosistema , Eucariontes/fisiología , Filogenia , Análisis de Secuencia de ADN
19.
Plant Physiol ; 177(1): 181-193, 2018 05.
Artículo en Inglés | MEDLINE | ID: mdl-29555786

RESUMEN

Diacylglyceryl-N,N,N-trimethylhomo-Ser (DGTS) is a nonphosphorous, polar glycerolipid that is regarded as analogous to the phosphatidylcholine in bacteria, fungi, algae, and basal land plants. In some species of algae, including the stramenopile microalga Nannochloropsis oceanica, DGTS contains an abundance of eicosapentaenoic acid (EPA), which is relatively scarce in phosphatidylcholine, implying that DGTS has a unique physiological role. In this study, we addressed the role of DGTS in N. oceanica We identified two DGTS biosynthetic enzymes that have distinct domain configurations compared to previously identified DGTS synthases. Mutants lacking DGTS showed growth retardation under phosphate starvation, demonstrating a pivotal role for DGTS in the adaptation to this condition. Under normal conditions, DGTS deficiency led to an increase in the relative amount of monogalactosyldiacylglycerol, a major plastid membrane lipid with high EPA content, whereas excessive production of DGTS induced by gene overexpression led to a decrease in monogalactosyldiacylglycerol. Meanwhile, lipid analysis of partial phospholipid-deficient mutants revealed a role for phosphatidylcholine and phosphatidylethanolamine in EPA biosynthesis. These results suggest that DGTS and monogalactosyldiacylglycerol may constitute the two major pools of EPA in extraplastidic and plastidic membranes, partially competing to acquire EPA or its precursors derived from phospholipids. The mutant lacking DGTS also displayed impaired growth and a lower proportion of EPA in extraplastidic compartments at low temperatures. Our results indicate that DGTS is involved in the adaptation to low temperatures through a mechanism that is distinct from the DGTS-dependent adaptation to phosphate starvation in N. oceanica.


Asunto(s)
Adaptación Biológica/fisiología , Enzimas/metabolismo , Metiltransferasas/metabolismo , Fosfatos/metabolismo , Estramenopilos/fisiología , Triglicéridos/metabolismo , Sitios de Unión , Proliferación Celular , Frío , Ácido Eicosapentaenoico/metabolismo , Enzimas/genética , Galactolípidos/metabolismo , Regulación de la Expresión Génica , Metiltransferasas/genética , Microalgas/fisiología , Mutación , Fosfolípidos/genética , Fosfolípidos/metabolismo , Filogenia , Estramenopilos/citología , Triglicéridos/genética
20.
Microb Ecol ; 75(3): 582-597, 2018 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-28942559

RESUMEN

The White Sea is a unique marine environment combining features of temperate and Arctic seas. The composition and abundance of photosynthetic picoeukaryotes (PPEs) were investigated in the land-fast ice of the White Sea, Russia, in March 2013 and 2014. High-throughput tag sequencing (Illumina MiSeq system) of the V4 region of the 18S rRNA gene was used to reveal the diversity of PPE ice community. The integrated PPE abundance varied from 11 × 106 cells/m2 to 364 × 106 cells/m2; the integrated biomass ranged from 0.02 to 0.26 mg С/m2. The composition of sea-ice PPEs was represented by 16 algae genera belonging to eight classes and three super-groups. Chlorophyta, especially Mamiellophyceae, dominated among ice PPEs. The detailed analysis revealed the latent diversity of Micromonas and Mantоniella. Micromonas clade E2 revealed in the subarctic White Sea ice indicates that the area of distribution of this species is wider than previously thought. We suppose there exists a new Micromonas clade F. Micromonas clade C and Minutocellulus polymorphus were first discovered in the ice and extend the modern concept of sympagic communities' diversity generally and highlights the importance of further targeting subarctic sea ice for microbial study.


Asunto(s)
Eucariontes/clasificación , Eucariontes/fisiología , Cubierta de Hielo/parasitología , Fotosíntesis , Filogenia , Regiones Árticas , Biodiversidad , Biomasa , Clorofila/análisis , Chlorophyta/clasificación , Chlorophyta/genética , Chlorophyta/fisiología , ADN/análisis , ADN/aislamiento & purificación , Eucariontes/genética , Eucariontes/aislamiento & purificación , Haptophyta/clasificación , Haptophyta/genética , Haptophyta/fisiología , Secuenciación de Nucleótidos de Alto Rendimiento , Cubierta de Hielo/química , ARN Ribosómico 18S/genética , Federación de Rusia , Estaciones del Año , Agua de Mar/parasitología , Estramenopilos/clasificación , Estramenopilos/genética , Estramenopilos/aislamiento & purificación , Estramenopilos/fisiología , Temperatura Ambiental
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