RESUMEN
Intertidal microphytobenthos (MPB) are a major contributor to primary production in estuarine ecosystems. While their biomass is highly variable at multiple spatial and temporal scales, the underlying drivers are as yet little understood. Both in situ sampling and remote-sensing techniques often lack the temporal resolution or coverage to simultaneously capture short-term (intratidal to daily) and longer-term (weekly to annual) biomass changes. Our field setup with in-situ NDVI sensors allowed us to study MPB surface biomass variability at high temporal resolution (10 mins) for up to two years in a freshwater euglenoid dominated mudflat, and a brackish and a marine diatom dominated mudflat. MPB biomass showed marked periodicities at multiple temporal scales: seasonal, spring-neap and intratidal. The diatom-dominated MPB community showed a seasonal biomass peak in winter, while the euglenoid-dominated community showed biomass peaks during spring and summer, probably caused by underlying divergent responses to mainly irradiance, temperature and wind-induced resuspension, and macrobenthos grazing. Spring-neap periodicity likely resulted from differential migratory responses of the MPB communities to variation in timing and duration of daylight exposure. In the freshwater community, upward migration only occurred when exposure duration was sufficiently long (≥4 h). In the diatom-dominated community, morning daylight exposure resulted in highest NDVI values. This study highlights the differences in MPB biomass dynamics between MPB communities within estuarine ecosystems, and underscores the great potential of high-resolution temporal NDVI monitoring for more accurate estimates of MPB biomass and primary production.
Asunto(s)
Biopelículas , Biomasa , Diatomeas , Monitoreo del Ambiente , Estaciones del Año , Diatomeas/fisiología , Monitoreo del Ambiente/métodos , Ecosistema , EuglénidosRESUMEN
This study presents the results of a complex survey of freshwater heterotrophic euglenoids in the Czech Republic, including both literature data and own field surveys of 469 sites visited in the course of three years. The checklist includes 189 taxa in 28 genera: Anisonema (10), Astasia (26), Atraktomonas (1), Calycimonas (2), Chasmostoma (1), Dinematomonas (3), Distigma (8), Dylakosoma (1), Entosiphon (4), Euglena (1), Gyropaigne (1), Heteronema (19), Jenningsia (11), Khawkinea (1), Lepocinclis (1), Menoidium (7), Neometanema (3), Notosolenus (18), Petalomonas (40), Phacus (1), Ploeotia (2), Pseudoperanema (7), Rhabdomonas (5), Scytomonas (1), Sphenomonas (5), Teloprocta (1) Tropidocyphus (1), Urceolus (4), and 4 species of uncertain identity. In addition, a general description of habitat types in which the taxa were found and a review of the current taxonomy and nomenclature of included taxa are provided. Several taxonomic and nomenclatural novelties are proposed, based on the review of morphological features, mostly applying to the genera Notosolenus and Jenningsia.
Asunto(s)
Euglénidos , República Checa , Euglénidos/clasificación , Euglénidos/genética , Lista de Verificación , Agua Dulce , Especificidad de la EspecieRESUMEN
Endo-ß-1,3-glucanases from several organisms have attracted much attention in recent years because of their capability for in vitro degrading ß-1,3-glucan as a critical step for both biofuels production and short-chain oligosaccharides synthesis. In this study, we biochemically characterized a putative endo-ß-1,3-glucanase (EgrGH64) belonging to the family GH64 from the single-cell protist Euglena gracilis. The gene coding for the enzyme was heterologously expressed in a prokaryotic expression system supplemented with 3% (v/v) ethanol to optimize the recombinant protein right folding. Thus, the produced enzyme was highly purified by immobilized-metal affinity and gel filtration chromatography. The enzymatic study demonstrated that EgrGH64 could hydrolyze laminarin (KM 23.5 mg ml-1,kcat 1.20 s-1) and also, but with less enzymatic efficiency, paramylon (KM 20.2 mg ml-1,kcat 0.23 ml mg-1 s-1). The major product of the hydrolysis of both substrates was laminaripentaose. The enzyme could also use ramified ß-glucan from the baker's yeast cell wall as a substrate (KM 2.10 mg ml-1, kcat 0.88 ml mg-1 s-1). This latter result, combined with interfacial kinetic analysis evidenced a protein's greater efficiency for the yeast polysaccharide, and a higher number of hydrolysis sites in the ß-1,3/ß-1,6-glucan. Concurrently, the enzyme efficiently inhibited the fungal growth when used at 1.0 mg/mL (15.4 µM). This study contributes to assigning a correct function and determining the enzymatic specificity of EgrGH64, which emerges as a relevant biotechnological tool for processing ß-glucans.
Asunto(s)
Euglena gracilis , Cinética , Polisacáridos/metabolismo , Hidrólisis , Saccharomyces cerevisiae/metabolismo , Especificidad por SustratoRESUMEN
Industrial development and urbanization has led to the diverse presence of metals in wastewater that are often improperly treated. The microalgae Euglena gracilis can tolerate high concentrations of metal via the excretion of organic metabolites, including phenolics. This study aims to evaluate how carbon amendment stimulates phenolic compound production by E. gracilis. The number, relative intensity and molecular composition of the phenolic compounds were significantly different between each of four carbon amended cultures (i.e., glutamic acid, malic acid, glucose, reduced glutathione) during the log phase. Phenolic compounds were mainly produced during the minimum growth rate, likely a response to stressful conditions. A better understanding of phenolic compounds production by E. gracilis and the impact of growth conditions will help identify conditions that favor certain phenolic compounds for dietary and metal chelation applications.
Asunto(s)
Euglena gracilis , Microalgas , Carbono/metabolismo , Euglena gracilis/metabolismo , Glucosa/metabolismo , MetabolómicaRESUMEN
Hydrological regimes are key in shaping the structure of phytoplankton communities in estuaries. Because anthropogenic disturbances often alter the quantity and quality of riverine inputs, this research focused on investigating phytoplankton dynamics in the St. Lucia Estuary, since being reconnected to the Mfolozi River. Due to the closed mouth state of the estuary, the input from the river resulted in oligohaline (≥5) conditions and the characteristic reverse salinity gradient to persist throughout the study (i.e. one year). Model results indicated that phytoplankton communities were structured by rainfall, light transmittance and depth, while shifts between dominant groups were driven by salinity and flow season. The persistence of chlorophytes and euglenophytes as the co-dominant functional group indicates the freshening and nutrient-enriched nature of the river. This study provides the first detailed account documenting the response of the phytoplankton community to recent restoration efforts in the St Lucia Estuary, a Ramsar Site.
Asunto(s)
Monitoreo del Ambiente/métodos , Estuarios , Fitoplancton/crecimiento & desarrollo , Ríos/química , Ciclo Hidrológico , Chlorophyta/crecimiento & desarrollo , Euglénidos/crecimiento & desarrollo , Dinámica Poblacional , Salinidad , Estaciones del Año , Sudáfrica , Movimientos del AguaRESUMEN
Morphological and ultrastructural changes induced by exposure to excess of organic matter were analyzed in Phacus brachykentron (Pochm.). The cells were isolated from sites in Matanza River, Buenos Aires, Argentina, which have a high degree of organic matter contamination coming from waste waters discharges of the meat industry. Master strains were cultured on soil water medium and a toxicity bioassay was performed. As a result of the enriched medium, several morphological and ultrastructural cellular alterations were observed by optical, scanning, and transmission electron microscopy. Among these, we can point out changes in cell dimensions, remarkable widening of some pellicle bands, increased number and volume of paramylon grains, displacement of the nucleus from the central to the lateral position, some chloroplasts with their thylakoids disordered, and cell lysis. The response to organic enrichment was very fast, i.e. during the 48h of the bioassay. Therefore, any significant increase of organic matter would rapidly affect wild euglenoids. Our results suggest that the alterations observed, such as the presence of large intracellular paramylon bodies or the deformation of euglenoid cells in natural samples, have the potential to be used as environmental bioindicators.