RESUMO
Small chrysomonads are important bacterivores in aquatic ecosystems with a high molecular diversity compared to low morphological differences observed by light microscopy. The high diversity of these morphologically almost indistinguishable species leads to the question to which extent their functional role in ecosystems differs and how their ecological traits can be defined. The present study investigates the prey size and population growth rate of different chrysomonad species. Eleven phylogenetically well-defined strains representing seven strains of heterotrophic and four strains of mixotrophic chrysomonads were compared. All investigated strains belonged to the same functional group of bacterivorous flagellates, feeding on the same bacteria size range, while population growth rates of chrysomonads depended on nutritional strategy and species-specific differences. We observed a high individual variability of growth rates within a population. Our results point to the necessity to consider not only differences in ecological traits among species but also among specimens within a population.
Assuntos
Chrysophyta , Chrysophyta/fisiologia , Chrysophyta/crescimento & desenvolvimento , Especificidade da Espécie , Processos Heterotróficos , FilogeniaRESUMO
Mixotrophic protists combine photosynthesis and phagotrophy to obtain energy and nutrients. Because mixotrophs can act as either primary producers or consumers, they have a complex role in marine food webs and biogeochemical cycles. Many mixotrophs are also phenotypically plastic and can adjust their metabolic investments in response to resource availability. Thus, a single species's ecological role may vary with environmental conditions. Here, we quantified how light and food availability impacted the growth rates, energy acquisition rates, and metabolic investment strategies of eight strains of the mixotrophic chrysophyte, Ochromonas. All eight Ochromonas strains photoacclimated by decreasing chlorophyll content as light intensity increased. Some strains were obligate phototrophs that required light for growth, while other strains showed stronger metabolic responses to prey availability. When prey availability was high, all eight strains exhibited accelerated growth rates and decreased their investments in both photosynthesis and phagotrophy. Photosynthesis and phagotrophy generally produced additive benefits: In low-prey environments, Ochromonas growth rates increased to maximum, light-saturated rates with increasing light but increased further with the addition of abundant bacterial prey. The additive benefits observed between photosynthesis and phagotrophy in Ochromonas suggest that the two metabolic modes provide nonsubstitutable resources, which may explain why a tradeoff between phagotrophic and phototrophic investments emerged in some but not all strains.
Assuntos
Chrysophyta , Ochromonas , Ochromonas/metabolismo , Fotossíntese , Luz , Clorofila/metabolismoRESUMO
The scientific community lacks models for the dynamic changes in population size structure that occur in colonial phytoplankton. This is surprising, as size is a key trait affecting many aspects of phytoplankton ecology, and colonial forms are very common. We aim to fill this gap with a new discrete, stochastic model of dynamic changes in phytoplankton colonies' population size structure. We use the colonial phytoplankton Dinobryon as a proof-of-concept organism. The model includes four stochastic functions-division, stomatocyst production, colony breakage, and colony loss-to determine Dinobryon population size structure and populations counts. Although the functions presented here are tailored to Dinobryon, the model is readily adaptable to represent other colonial taxa. We demonstrate how fitting our model to in situ observations of colony population size structure can provide a powerful approach to explore colony size dynamics. Here, we have (1) collected high-frequency in situ observations of Dinobryon in Lac (Lake) Montjoie (Quebec, Canada) in 2013 with a moored Imaging FlowCytobot (IFCB) and (2) fit the model to those observations with a genetic algorithm solver that extracts parameter estimates for each of the four stochastic functions. As an example of the power of this model-data integration, we also highlight ecological insights into Dinobryon colony size and stomatocyst production. The Dinobryon population was enriched in larger, flagellate-rich colonies near bloom initiation and shifted to smaller and emptier colonies toward bloom decline.
Assuntos
Chrysophyta , Fitoplâncton , Fitoplâncton/genética , Densidade Demográfica , Citometria de Fluxo , LagosRESUMO
Stomatocysts of the rare heterotrophic chrysophyte, Paraphysomonas caelifrica, were discovered from a shallow ephemeral pond Tavolgasai ("Orenburgskiy" State Nature Reserve, Orenburg Region, Russia). Morphology of stomatocysts was studied using scanning electron microscopy. Stomatocysts of P. caelifrica are spherical and smooth with a cylindrical collar surrounding the regular pore. So, they do not belong to the stomatocyst 1 Duff and Smol as previously thought. The description of a new stomatocyst morphotype is provided.
Assuntos
Chrysophyta , Estramenópilas , Microscopia Eletrônica de Varredura , Federação Russa , FilogeniaRESUMO
BACKGROUND: Algae are prominent producers of carotenoids and polyunsaturated fatty acids which are greatly prized in the food and pharmaceutic industry. Fucoxanthin represents a notable high-value carotenoid produced exclusively by algae. Its benefits range far beyond just antioxidant activity and include cancer prevention, anti-diabetes, anti-obesity, and many other positive effects. Accordingly, large-scale microalgae cultivation to produce fucoxanthin and polyunsaturated fatty acids is still under intensive development in the commercial and academic sectors. Industrially exploitable strains are predominantly derived from marine species while comparable freshwater fucoxanthin producers have yet to be explored. RESULTS: In this study, we searched for freshwater fucoxanthin producers among photoautotrophic flagellates including members of the class Chrysophyceae. The initial screening turned our attention to the chrysophyte alga Hibberdia magna. We performed a comprehensive cultivation experiments using a temperature × light cross-gradient to assess the impact of these conditions on the target compounds productivity. Here we present the observations that H. magna simultaneously produces fucoxanthin (max. 1.2% dry biomass) and polyunsaturated fatty acids (max. ~ 9.9% dry biomass) and is accessible to routine cultivation in lab-scale conditions. The highest biomass yields were 3.73 g L-1 accompanied by maximal volumetric productivity of 0.54 g L-1 d-1 which are comparable values to marine microalgae fucoxanthin producers in phototrophic mode. H. magna demonstrated different optimal conditions for biomass, fucoxanthin, and fatty acid accumulation. While maximal fucoxanthin productivities were obtained in dim light and moderate temperatures (23 °C× 80 µmol m-2 s-1), the highest PUFA and overall biomass productivities were found in low temperature and high light (17-20 °C × 320-480 µmol m-2 s-1). Thus, a smart biotechnology setup should be designed to fully utilize H. magna biotechnological potential. CONCLUSIONS: Our research brings pioneer insight into the biotechnology potential of freshwater autotrophic flagellates and highlights their ability to produce high-value compounds. Freshwater fucoxanthin-producing species are of special importance as the use of sea-water-based media may increase cultivation costs and prohibits inland microalgae production.
Assuntos
Chrysophyta , Microalgas , Ácidos Graxos Insaturados , Xantofilas , Ácidos Graxos , Carotenoides , BiomassaRESUMO
Disgusting fishy odor could break out inside oligotrophic drinking waterbody in winter with low temperature. Nevertheless, fishy odor-producing algae and corresponding fishy odorants were not very clear, odor contribution of fishy odorant and odor-producing algae to overall odor profile were also not well understood. In this study, the fishy odorants, produced by four algae separated from Yanlong Lake, were identified simultaneously. Odor contribution of identified odorant, separated algae to overall fishy odor profile were both evaluated. The results indicated Yanlong Lake was mainly associated with fishy odor (flavor profile analysis (FPA) intensity: 6), eight, five, five and six fishy odorants were identified and determined in Cryptomonas ovate, Dinobryon sp., Synura uvella, Ochromonas sp., respectively, which were separated and cultured from water source. Totally sixteen odorants with concentration range of 90-880 ng/L, including hexanal, heptanal, 2,4-heptadienal, 1-octen-3-one, 1-octen-3-ol, octanal, 2-octenal, 2,4-octadienal, nonanal, 2-nonenal, 2,6-nonadienal, decanal, 2-decenal, 2,4-decadienal, undecanal, 2-tetradecanone, were verified in separated algae and associated with fishy odor. Although more odorants' odor activity value (OAV) were lower than one, approximately 89%, 91%, 87%, 90% of fishy odor intensities could be explained by reconstituting identified odorants for Cryptomonas ovate, Dinobryon sp., Synura uvella, Ochromonas sp., respectively, suggesting synergistic effect could exist among identified odorants. By calculating and evaluating total odorant production, total odorant OAV and cell odorant yield of separated algae, odor contribution rank to overall fishy odor should be Cryptomonas ovate (28.19%), Dinobryon sp. (27.05%), Synura uvella (24.27%), Ochromonas sp. (20.49%). This is the first study for identifying fishy odorants from four actually separated odor-producing algae simultaneously, this is also for the first time evaluating and explaining odor contribution of identified odorant, separated algae to overall odor profile comprehensively, this study will supply more understanding for controlling and managing fishy odor in drinking water treatment plant.
Assuntos
Chrysophyta , Água Potável , Odorantes/análise , Água Potável/análise , Temperatura , Temperatura BaixaRESUMO
Bioassays using cultures of the toxic haptophyte Prymnesium parvum and the ciliate Cyclidium sp. as prey were conducted to test the effect of pH (rangeâ¯=â¯6.5 - 8.5), salinity (rangeâ¯=â¯1.50 - 7.50), and a combination of pH and salinity on the toxicity of P. parvum. pH had a significant effect on P. parvum toxicity. Toxicity was rapidly (within 24 hr) induced by increasing pH of the medium, or reduced by lowering pH. Conversely, lowering salinity reduced toxicity, albeit less effectively compared to pH, and P. parvum cells remained toxic at the lowest values tested (1.50 at pH 7.5). An additional effect between pH and salinity was also observed: low salinity combined with low pH led to not only decreased toxicity, but also resulted in lower P. parvum growth rates. Such effects of pH and salinity on P. parvum growth and toxicity provide insight into the environmental factors supporting community dominance and toxic blooms of the alga.
Assuntos
Chrysophyta , Haptófitas , Salinidade , Concentração de Íons de HidrogênioRESUMO
Mallomonas is the largest and most speciose genus within the Synurales, a monophyletic clade of siliceous scale-bearing organisms within the class Chrysophyceae. The genus consists of unicellular, motile, photosynthetic organisms found in freshwater localities worldwide. Mallomonas diverged from other synurophytes during the lower Cretaceous at approximately 130 Ma. Recent discoveries of fossil species were used to examine shifts in scale and cell size over geologic time. On average, scales of fossil species were 2.5 times larger than those produced by modern species. However, a smaller subset of extinct fossil taxa lacking modern analogs had scales over four times larger than modern species, and the largest recorded specimens were six times larger. Data from modern species were further used to develop a model relating scale size to cell size, and applied to the fossil specimens. Based on the model, the mean size of fossil cells was almost twice as long and 50% wider compared to modern species, and cells of taxa lacking modern analogs close to three times as large. These large cells, covered with robust siliceous scales, were likely slow swimmers requiring significant energy to maintain their position in the water column, and possibly prone to increased predation.
Assuntos
Chrysophyta , Estramenópilas , Fósseis , Água Doce , FilogeniaRESUMO
Mixotrophs are increasingly recognized for their wide distribution in aquatic ecosystems and significant contributions to biogeochemical cycling. Many taxa within the phyla Chrysophyta, Cryptophyta, and Haptophyta are capable of phago-mixotrophy, however, phagotrophy in the Chlorophyta remains controversial due to insufficient research and solid evidence. In this study, we identified a new strain, Picochlorum sp. GLMF1 (Trebouxiophyceae), using 18S rRNA gene analysis and morphological observations. It displayed multi-cell division through autosporulation (two- or four-cell daughters) and has two unequal flagella that have never been reported in the genus Picochlorum. By using multiple methods, including 3D bioimaging analysis, acidic food vacuole-like compartment staining, and prey reduction calculation, we discovered and confirmed bacterivory in Picochlorum, which provided strong evidence for phago-mixotrophy in this green alga. In addition, we found that Picochlorum sp. GLMF1 cannot grow under complete darkness or prey-depleted conditions, suggesting that both light and bacteria are indispensable for this strain, and its mixotrophic nutrition mode is obligate. Like other phago-phototrophs, Picochlorum sp. GLMF1 is capable of regulating their growth and ingestion rates according to light intensity and inorganic nutrient concentration. The confirmation of mixotrophy in this Picochlorum strain advances our understanding of the trophic roles of green algae, as well as the photosynthetic picoeukaryotes, in marine microbial food webs.
Assuntos
Clorófitas , Chrysophyta , Haptófitas , Clorófitas/genética , Criptófitas/fisiologia , EcossistemaRESUMO
Tribonema biomass is considered promising biorefinery feedstock for the co-production of biodiesel and valuable bioproducts; however, the extraction of these useful compounds produces large amounts of algal residues, which produce increased environmental concerns. Herein, cellulose was extracted from the waste residue of T. utriculosum via alkalization and bleaching, followed by the production of high-value-added cellulose nanocrystals (CNCs) via acid hydrolysis. The hydrolysis was performed with 60% (wt%) H2SO4 at a yield of 13.31%, resulting in the generation of rod-shaped nanoparticles averaging 39.5 nm in diameter and 239.2 nm in length. The structural characterization analysis revealed that the prepared CNCs had high crystallinity (73.0%) due to the removal of non-cellulose components and amorphous regions by chemical treatment, as well as possessing good aqueous suspension stability (zeta potential = - 40.1 mV). Although the CNCs showed lower thermal stability than extracted cellulose, they spanned a broader temperature range due to two-stage degradation behaviour, with higher residue weight (16.7%). This work represents the first report on the preparation of a high-value-added industrial product, CNCs, from the filamentous microalga T. utriculosum, aiming to maximize benefits from waste algal residue reutilization.
Assuntos
Celulose/química , Chrysophyta/química , Microalgas/química , Nanopartículas/química , HidróliseRESUMO
BACKGROUND AND AIMS: While nuclear DNA content variation and its phenotypic consequences have been well described for animals, vascular plants and macroalgae, much less about this topic is known regarding unicellular algae and protists in general. The dearth of data is especially pronounced when it comes to intraspecific genome size variation. This study attempts to investigate the extent of intraspecific variability in genome size and its adaptive consequences in a microalgal species. METHODS: Propidium iodide flow cytometry was used to estimate the absolute genome size of 131 strains (isolates) of the golden-brown alga Synura petersenii (Chrysophyceae, Stramenopiles), identified by identical internal transcribed spacer (ITS) rDNA barcodes. Cell size, growth rate and genomic GC content were further assessed on a sub-set of strains. Geographic location of 67 sampling sites across the Northern hemisphere was used to extract climatic database data and to evaluate the ecogeographical distribution of genome size diversity. KEY RESULTS: Genome size ranged continuously from 0.97 to 2.02 pg of DNA across the investigated strains. The genome size was positively associated with cell size and negatively associated with growth rate. Bioclim variables were not correlated with genome size variation. No clear trends in the geographical distribution of strains of a particular genome size were detected, and strains of different genome size occasionally coexisted at the same locality. Genomic GC content was significantly associated only with genome size via a quadratic relationship. CONCLUSIONS: Genome size variability in S. petersenii was probably triggered by an evolutionary mechanism operating via gradual changes in genome size accompanied by changes in genomic GC content, such as, for example, proliferation of transposable elements. The variation was reflected in cell size and relative growth rate, possibly with adaptive consequences.
Assuntos
Chrysophyta , Genoma de Planta , Evolução Biológica , Tamanho do Genoma , Genoma de Planta/genética , PloidiasRESUMO
The chrysophyte genus Dinobryon Ehrenberg consists of 44 taxa, which occur in freshwaters, rarely marine waters, mostly in temperate regions of the world. The taxa of Dinobryon produce characteristic solitary or dendroid colonies and resting stages called stomatocysts. Only 20 Dinobryon taxa have information on produced stomatocysts and only four stomatocysts are reliably linked with vegetative stages using modern identification standards employing scanning electron microscopy (SEM) analyses. In this study, an encysted material of Dinobryon pediforme (Lemmermann) Steinecke was collected in two lakes in contrasting regions of Poland. Light microscopy (LM) and scanning electron microscopy (SEM) analyses revealed that Dinobryon pediforme produces stomatocyst #61, Piatek J. that is described here as new morphotype following the International Statospore Working Group (ISWG) guidelines. This raises to five the number of reliable links between vegetative stages of Dinobryon species and corresponding stomatocysts. Phenotypic similarities between Dinobryon species and their stomatocysts, analysed for five reliably established links, showed no relationships in size and shape between loricas and stomatocysts belonging to the same species. The morphological characters of loricas and stomatocysts mapped onto the phylogenetic tree of the five Dinobryon species revealed only little congruence between their morphology and phylogenetic relationships.
Assuntos
Chrysophyta/ultraestrutura , Chrysophyta/classificação , Chrysophyta/crescimento & desenvolvimento , Microscopia Eletrônica de Varredura , Filogenia , Polônia , Especificidade da EspécieRESUMO
Off-flavor events in tap water have been reported from various regions of Japan. Fishy smell is the second most common off-flavor in Japan and Uroglena americana (U. americana) is known to be a major contributor to the smell. However, the causative compound of the smell it produces still remains unrevealed to the best of our knowledge. In this study, an exploration of odorous aldehydes and ketones originating from U. americana was performed with a view to discovering a possible candidate substance of causative compounds. Environmental samples containing U. americana colony and cultured media with U. americana were analyzed with two high resolution mass spectrometers, one of them is coupled with liquid chromatography (LC-HRMS), and the other is with gas chromatography and a sniffing port (GC-O-HRMS). Multivariate analyses (MVA) were utilized to explore a compound that is likely to be odorous aldehydes or ketones with a reduced time of exploration. A combination of LC-HRMS and MVA resulted in the selection of one candidate substance and its formula was determined to be C13H20O3 on the basis of its accurate mass and natural isotopic pattern. The candidate substance underwent GC-O-HRMS analyses and milk-like smell was detected at around its retention time. Although the detected smell was different from fishy smell, it is expected that the fishy smell is caused by multiple compounds to which the candidate substance belongs. First generation product ion spectra of the candidate substance suggested that it contains a hydroxyl group, a cyclohexene ring, and a ketone moiety.
Assuntos
Aldeídos/análise , Chrysophyta/fisiologia , Cetonas/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Japão , Espectrometria de Massas , Análise Multivariada , Odorantes/análise , Olfatometria/métodos , Olfato , PaladarRESUMO
Chrysophyte algae produce a siliceous stage in their life cycle, through either asexual or sexual reproduction, known as a cyst. Cysts form in response to shifts in environmental conditions, population density, or predation pressure, and upon germination provide a seed source for future populations. Cysts are morphologically distinct for each species, and since their remains become part of the sediment or fossil record cysts are valuable tools in ecological and paleolimnological investigations. However, their value as biological indicators is limited because the vast majority of cyst morphotypes have not been linked to specific vegetative species. In the current work, an exquisitely preserved and morphologically complex cyst type is described from a 48 million year old early Eocene fossil site. This finding is remarkable since many of the cysts were still associated with components of the living vegetative cells that produced them, enabling the morphotype to be immediately linked to the synurophyte, Mallomonas ampla. Fusion of identifiable components of the living cell post cyst formation is unknown in modern investigations. The identification of the cyst structure for M. ampla could be valuable in determining cyst morphotypes for other species in the lineage.
Assuntos
Chrysophyta/ultraestrutura , Fósseis , Regiões Árticas , Água Doce , Lagos , Microscopia Eletrônica de Varredura , Territórios do Noroeste , Estruturas Vegetais/ultraestruturaRESUMO
The class Eustigmatophyceae includes mostly coccoid, freshwater algae, although some genera are common in terrestrial habitats and two are primarily marine. The formal classification of the class, developed decades ago, does not fit the diversity and phylogeny of the group as presently known and is in urgent need of revision. This study concerns a clade informally known as the Pseudellipsoidion group of the order Eustigmatales, which was initially known to comprise seven strains with oval to ellipsoidal cells, some bearing a stipe. We examined those strains as well as 10 new ones and obtained 18S rDNA and rbcL gene sequences. The results from phylogenetic analyses of the sequence data were integrated with morphological data of vegetative and motile cells. Monophyly of the Pseudellipsoidion group is supported in both 18S rDNA and rbcL trees. The group is formalized as the new family Neomonodaceae comprising, in addition to Pseudellipsoidion, three newly erected genera. By establishing Neomonodus gen. nov. (with type species Neomonodus ovalis comb. nov.), we finally resolve the intricate taxonomic history of a species originally described as Monodus ovalis and later moved to the genera Characiopsis and Pseudocharaciopsis. Characiopsiella gen. nov. (with the type species Characiopsiella minima comb. nov.) and Munda gen. nov. (with the type species Munda aquilonaris) are established to accommodate additional representatives of the polyphyletic genus Characiopsis. A morphological feature common to all examined Neomonodaceae is the absence of a pyrenoid in the chloroplasts, which discriminates them from other morphologically similar yet unrelated eustigmatophytes (including other Characiopsis-like species).
Assuntos
RNA Ribossômico 16S , Chrysophyta/genética , DNA Ribossômico , Filogenia , Análise de Sequência de DNARESUMO
Grazing behaviour between protozoa and phytoplankton exists widely in planktonic ecosystems. Poterioochromonas malhamensis is a well-known and widespread mixotrophic flagellate, which is recognized to play an important role within marine and freshwater planktonic ecosystems and regarded as the greatest contamination threat for mass algal cultures of Chlorella. In this study, a comprehensive range of factors, including morphological characters, biochemical compositions, and specific growth rate of ten species or strains of Chlorella, were evaluated for their effect on the feeding ability of P. malhamensis, which was assessed by two parameters: the clearance rate of P. malhamensis on Chlorella spp. and the specific growth rate of P. malhamensis. The results showed that the clearance rate of P. malhamensis was negatively correlated with cell wall thickness and specific growth rate of Chlorella spp., while the specific growth rate of P. malhamensis was positively correlated with carbohydrate percentage and C/N ratio and negatively correlated with protein, lipid percentage, and nitrogen mass. In conclusion, the factors influencing feeding selectivity include not only the morphological character and chemical composition of Chlorella, but also its population dynamics. Our study provides useful insights into the key factors that affect the feeding selectivity of P. malhamensis and provides basic and constructive data to help in screening for grazing-resistant microalgae.
Assuntos
Chlorella/fisiologia , Chrysophyta/fisiologia , Cadeia Alimentar , Microalgas/fisiologia , Parede Celular/fisiologia , Dieta , Dinâmica PopulacionalRESUMO
Melting summer snow in the Austrian Alps exhibited a yellowish bloom that was mainly comprised of an unidentified unicellular chrysophyte. Molecular data (18S rRNA and rbcL genes) showed a close relationship to published sequences from an American pond alga formerly identified as Kremastochrysis sp. The genera Kremastochrysis and Kremastochrysopsis are morphologically distinguished by the number of flagella observed with the light microscope, and therefore we assigned the Austrian snow alga and an American pond alga to the genus Kremastochrysopsis. Transmission and scanning electron microscopy revealed that swimming cells had two flagella oriented in opposite directions, typical for the Hibberdiales. Molecular phylogenetic analyses showed that both new species were closely related to Hibberdia. Kremastochrysopsis ocellata, the type species and only known species, has two chloroplasts per cell and the zoospores have red eyespots. Our two organisms had only a single chloroplast and no zoospore eyespot, but their gene sequences differed substantially. Therefore, we described two new species, Kremastochrysopsis austriaca sp. nov and Kremstochrysopsis americana sp. nov. When grown in culture, both taxa showed a characteristic hyponeustonic growth (hanging below the water surface), whereas older immotile cells grew at the bottom of the culture vessel. Ecologically, Kremastochrysopsis austriaca sp. nov., which caused snow discolorations, had no close phylogenetic relationships to other psychrophilic chrysophytes, for example, Chromulina chionophilia, Hydrurus sp., and Ochromonas-like flagellates.
Assuntos
Cloroplastos , Chrysophyta , Áustria , Filogenia , RNA Ribossômico 16S , RNA Ribossômico 18S , Análise de Sequência de DNARESUMO
Unicellular protists can biomineralize spatially complex and functional shells. A typical cell of the photosynthetic synurophyte Mallomonas is covered by about 60-100 silica scales. Their geometric arrangement, the so-called scale case, mainly depends on the species and on the cell cycle. In this study, the scale case of the synurophyte Mallomonas was preserved in aqueous suspension using high-pressure freezing (HPF). From this specimen, a three-dimensional (3D) data set spanning a volume of about 25.6⯵mâ¯×â¯19.2⯵mâ¯×â¯4.2⯵m with a voxel size of 12.5â¯nmâ¯×â¯12.5â¯nmâ¯×â¯25.0â¯nm was collected by Cryo-FIB SEM in 3â¯h and 24â¯min. SEM imaging using In-lens SE detection allowed to clearly differentiate between mineralized, curved scales of less than 0.2⯵m thickness and organic cellular ultrastructure or vitrified ice. The three-dimensional spatial orientations and shapes of a minimum set of scales (Nâ¯=â¯13) were identified by visual inspection, and manually segmented. Manual and automated segmentation approaches were comparatively applied to one arbitrarily selected reference scale using the differences in grey level between scales and other constituents. Computational automated routines and principal component analysis of the experimentally extracted data created a realistic mathematical model based on the Fibonacci pattern theory. A complete in silico scale case of Mallomonas was reconstructed showing an optimized scale coverage on the cell surface, similarly as it was observed experimentally. The minimum time requirements from harvesting the living cells to the final scale case determination by Cryo-FIB SEM and computational image processing are discussed.
Assuntos
Chrysophyta/ultraestrutura , Microscopia Crioeletrônica , Imageamento Tridimensional , Chrysophyta/fisiologia , Processamento de Imagem Assistida por Computador , Microscopia Eletrônica de VarreduraRESUMO
Human viruses are ubiquitous contaminants in surface waters, where they can persist over extended periods of time. Among the factors governing their environmental persistence, the control (removal or inactivation) by microorganisms remains poorly understood. Here, we determined the contribution of indigenous bacteria and protists to the decay of human viruses in surface waters. Incubation of echovirus 11 (E11) in freshwater from Lake Geneva and seawater from the Mediterranean Sea led to a 2.5-log10 reduction in the infectious virus concentration within 48 h at 22°C, whereas E11 was stable in sterile controls. The observed virus reduction was attributed to the action of both bacteria and protists in the biologically active matrices. The effect of microorganisms on viruses was temperature dependent, with a complete inhibition of microbial virus control in lake water at temperatures of ≤16°C. Among three protist isolates tested (Paraphysomonas sp., Uronema marinum, and Caecitellus paraparvulus), Caecitellus paraparvulus was particularly efficient at controlling E11 (2.1-log10 reduction over 4 days with an initial protist concentration of 103 cells ml-1). In addition, other viruses (human adenovirus type 2 and bacteriophage H6) exhibited different grazing kinetics than E11, indicating that the efficacy of antiviral action also depended on the type of virus. In conclusion, indigenous bacteria and protists in lake water and seawater can modulate the persistence of E11. These results pave the way for further research to understand how microorganisms control human viral pathogens in aquatic ecosystems and to exploit this process as a treatment solution to enhance microbial water safety.IMPORTANCE Waterborne human viruses can persist in the environment, causing a risk to human health over long periods of time. In this work, we demonstrate that in both freshwater and seawater environments, indigenous bacteria and protists can graze on waterborne viruses and thereby reduce their persistence. We furthermore demonstrate that the efficiency of the grazing process depends on temperature, virus type, and protist species. These findings may facilitate the design of biological methods for the disinfection of water and wastewater.
Assuntos
Cadeia Alimentar , Lagos , Viabilidade Microbiana , Viroses/virologia , Fenômenos Fisiológicos Virais , Doenças Transmitidas pela Água/virologia , Oceano Atlântico , Fenômenos Fisiológicos Bacterianos , Chrysophyta/fisiologia , Lagos/microbiologia , Lagos/parasitologia , Lagos/virologia , Mar Mediterrâneo , Oligoimenóforos/fisiologia , Água do Mar/microbiologia , Água do Mar/parasitologia , Água do Mar/virologia , Espanha , Especificidade da Espécie , Estramenópilas/fisiologia , Suíça , Vírus/classificaçãoRESUMO
Species delimitation in protists is still a challenge, attributable to the fact that protists are small, difficult to observe and many taxa are poor in morphological characters, whereas most current phylogenetic approaches only use few marker genes to measure genetic diversity. To address this problem, we assess genome-level divergence and microevolution in strains of the protist Poteriospumella lacustris, one of the first free-living, nonmodel organisms to study genome-wide intraspecific variation. Poteriospumella lacustris is a freshwater protist belonging to the Chrysophyceae with an assumed worldwide distribution. We examined three strains from different geographic regions (New Zealand, China, and Austria) by sequencing their genomes with the Illumina and PacBio platforms. The assembled genomes were small with 49-55 Mb but gene-rich with 16,000-19,000 genes, of which â¼8,000 genes could be assigned to functional categories. At least 68% of these genes were shared by all three species. Genetic variation occurred predominantly in genes presumably involved in ecological niche adaptation. Most surprisingly, we detected differences in genome ploidy between the strains (diploidy, triploidy, and tetraploidy). In analyzing intraspecific variation, several mechanisms of diversification were identified including SNPs, change of ploidy and genome size reduction.