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Pablo Castillejo, Susana Chamorro, Luis Paz, Carla Heinrich, Ivonne Carrillo, Jose G Salazar, Juan C Navarro, Eduardo A Lobo
Epilithic diatom communities are particularly suitable for the evaluation of freshwater quality. In Ecuador, however, no water quality index includes this biotic parameter. This work is the first attempt in the country to determine the composition of epilithic diatom communities associated with different degrees of eutrophication. This was accomplished by measuring physical, chemical and microbiological variables at five sampling sites along the Pita River, Ecuador, from August to December 2016. The results indicate a clear gradient of eutrophication from sampling sites P1 (good water) in the upper reaches to P5 (bad water) located in the lower reaches...
April 11, 2018: Comptes Rendus Biologies
Junzi Liu, Lan Cheng
An atomic mean-field (AMF) spin-orbit (SO) approach within exact two-component theory (X2C) is reported, thereby exploiting the exact decoupling scheme of X2C, the one-electron approximation for the scalar-relativistic contributions, the mean-field approximation for the treatment of the two-electron SO contribution, and the local nature of the SO interactions. The Hamiltonian of the proposed SOX2CAMF scheme comprises the one-electron X2C Hamiltonian, the instantaneous two-electron Coulomb interaction, and an AMF SO term derived from spherically averaged Dirac-Coulomb Hartree-Fock calculations of atoms; no molecular relativistic two-electron integrals are required...
April 14, 2018: Journal of Chemical Physics
Foudhil Bouakline
We report strong evidence of Berry phase effects in intense laser dissociation of D2 + molecules, manifested as Aharonov-Bohm-like oscillations in the photofragments angular distribution (PAD). Our calculations show that this interference pattern strongly depends on the parity of the diatom initial rotational state, (-1)j . Indeed, the PAD local maxima (minima) observed in one case (j odd) correspond to local minima (maxima) in the other case (j even). Using simple topological arguments, we clearly show that such interference conversion is a direct signature of the Berry phase...
April 12, 2018: Journal of Physical Chemistry Letters
Penelope A Ajani, Arjun Verma, Malwenn Lassudrie, Martina A Doblin, Shauna A Murray
A new species belonging to the toxin producing diatom genus Pseudo-nitzschia, P. hallegraeffii sp. nov., is delineated and described from the East Australian Current (EAC). Clonal cultures were established by single cell isolation from phytoplankton net hauls collected as part of a research expedition in the EAC region in 2016 on the RV Investigator. Cultures were assessed for their morphological and genetic characteristics, their sexual compatibility with other Pseudo-nitzschia species, and their ability to produce domoic acid...
2018: PloS One
Tatsuhiro Nomaguchi, Yoshiaki Maeda, Yue Liang, Tomoko Yoshino, Toru Asahi, Tsuyoshi Tanaka
Microalgal biofuels are desirable alternatives for traditional liquid fuels, but further improvements of productivity are necessary for microalgal biofuels to be economically feasible. As strategies for improving lipid productivity, repression of lipid degradation has a great potential because the lipid accumulation level is determined by a balance between lipid synthesis and degradation. However, studies of lipid degradation and its primary functioning enzyme triacylglycerol (TAG) lipases in microalgae are currently limited...
April 5, 2018: Journal of Bioscience and Bioengineering
Esther Bautista-Chamizo, Marta Sendra, Ángeles Cid, Marta Seoane, Manoela Romano de Orte, Inmaculada Riba
To evaluate the effects related to the combination of potential future changes in pH, temperature and salinity on microalgae, a laboratory experiment was performed using the marine diatom Phaeodactylum tricornutum. Populations of this species were exposed during 48h to a three-factor experimental design (3×2×2) with two artificial pH values (6, 7.4), two levels of temperature (23°C, 28°C), two levels of salinity (34psu, 40psu) and a control (pH8, Temp 23°C, Sal 34psu). The effects on growth, cell viability, metabolic activity, and inherent cell properties (size, complexity and autofluorescence) of P...
April 4, 2018: Science of the Total Environment
Hakuto Kageyama, Yoshito Tanaka, Teruhiro Takabe
Betaine (trimethylglycine) is an important compatible solute that accumulates in response to abiotic stresses such as drought and salinity. Biosynthetic pathways of betaine have been extensively studied, but it remains to be clarified on algae. A diatom Thalassiosira pseudonana CCMP1335 is an important component of marine ecosystems. Here we show that the genome sequence of Thalassiosira suggests the presence of two biosynthetic pathways for betaine, via three step methylation of glycine and via two step oxidation of choline...
March 30, 2018: Plant Physiology and Biochemistry: PPB
Alexandra A Popova, Ulla Rasmussen, Tatiana A Semashko, Vadim M Govorun, Olga A Koksharova
Various species of cyanobacteria, diatoms and dinoflagellates are capable of synthesizing the non-proteinogenic neurotoxic amino acid β-N-methylamino-L-alanine (BMAA), which is known to be a causative agent of human neurodegeneration. Similar to most cyanotoxins, the biological and ecological functions of BMAA in cyanobacteria are unknown. In this study, we show for the first time that BMAA, in micromolar amounts, inhibits the formation of heterocysts (specialized nitrogen-fixing cells) in heterocystous, diazotrophic cyanobacteria (Anabaena sp...
April 6, 2018: Environmental Microbiology Reports
Teofil Nakov, Jeremy M Beaulieu, Andrew J Alverson
Patterns of species richness are commonly linked to life history strategies. In diatoms, an exceptionally diverse lineage of photosynthetic heterokonts important for global photosynthesis and burial of atmospheric carbon, lineages with different locomotory and reproductive traits differ dramatically in species richness, but any potential association between life history strategy and diversification has not been tested in a phylogenetic framework. We constructed a time-calibrated, 11-gene, 1151-taxon phylogeny of diatoms - the most inclusive diatom species tree to date...
April 6, 2018: New Phytologist
Esperança Gacia, Teresa Buchaca, Nayeli Bernal-Mendoza, Ibor Sabás, Enric Ballesteros, Marc Ventura
Submersed aquatic plants are a key component of shallow, clear water lakes contributing to primary production and water quality. High mountain lakes are naturally fishless although invasive trout and most recently minnows have been introduced causing a major impact on fauna richness. The Pyrenean high mountain range has preserved soft-water oligotrophic boreal isoetids in their southern limit of distribution but the recent fish introduction is a potential factor of stress that needs to be addressed. We here work under the hypothesis that due to contrasting ecological features, trout will not be heavily affecting quillwort populations while minnows will have a stronger effect on zooplankton and zoobenthos that will promote algal growth and reduce light availability for the underwater meadows...
2018: Frontiers in Plant Science
Hui Wang, Yan Zhang, Lin Chen, Wentao Cheng, Tianzhong Liu
Fucoxanthin and eicosapentaenoic acid (EPA) provide significant health benefits for human population. Diatom is a potential natural livestock for the combined production of EPA and fucoxanthin. In this study, first, the effects of three important parameters including light intensity, nitrogen concentration and salinity were evaluated for the production of EPA and fucoxanthin in two diatom strains Phaeodactylum tricornutum and Cylindrotheca fusiformis. And then, two steps method based on light intensity were applied to produce EPA and fucoxanthin in large scale...
April 4, 2018: Bioprocess and Biosystems Engineering
Nadia Ruocco, Susan Costantini, Valerio Zupo, Chiara Lauritano, Davide Caramiello, Adrianna Ianora, Alfredo Budillon, Giovanna Romano, Genoveffa Nuzzo, Giuliana D'Ippolito, Angelo Fontana, Maria Costantini
Diatoms are unicellular algae playing a key role as photosynthetic organisms in the world's ocean food webs. The chemical ecology of planktonic diatoms is well documented, but few studies have reported on the effects of benthic diatoms on their consumers, also due to difficulties in the collection, quantification and massive culturing of benthic species. Here for the first time we investigate the effects of feeding on two abundantly occurring benthic diatoms, Nanofrustulum shiloi and Cylindrotheca closterium, isolated from the leaves of the seagrass Posidonia oceanica, on the sea urchin Paracentrotus lividus...
April 4, 2018: Scientific Reports
J Curt Stager, Brendan Wiltse, J Bradford Hubeny, Eric Yankowsky, David Nardelli, Richard Primack
Recent shifts in the ecological condition of Walden Pond, MA, are of potentially wide interest due to the lake's importance as a cultural, historical, and recreational resource in addition to its scientific value as an indicator of local and global environmental change. Algal microfossils in six sediment cores document changes in hydroclimate and trophic status of the lake during the last 1800 years and extend two previous sediment core records of shorter length. Low percentages of planktonic diatoms in the longest cores (WAL-3, WAL-15) indicate shallowing and/or greater water clarity associated with a relatively arid interval during the Medieval Climate Anomaly, ca...
2018: PloS One
Paulo R F Rocha, Alexandra D Silva, Lia Godinho, Willem Dane, Pedro Estrela, Lode K J Vandamme, Jose B Pereira-Leal, Dago M de Leeuw, Ricardo B Leite
Diatoms are photosynthetic microalgae, a group with a major environmental role on the planet due to the biogeochemical cycling of silica and global fixation of carbon. However, they can evolve into harmful blooms through a resourceful communication mechanism, not yet fully understood. Here, we demonstrate that a population of diatoms under darkness show quasi-periodic electrical oscillations, or intercellular waves. The origin is paracrine signaling, which is a feedback, or survival, mechanism that counteracts changes in the physicochemical environment...
April 3, 2018: Scientific Reports
Xianming Kong, Qian Yu, Erwen Li, Rui Wang, Qing Liu, Alan X Wang
Diatomaceous earth-otherwise called diatomite-is essentially composed of hydrated biosilica with periodic nanopores. Diatomite is derived from fossilized remains of diatom frustules and possesses photonic-crystal features. In this paper, diatomite simultaneously functions as the matrix of the chromatography plate and the substrate for surface-enhanced Raman scattering (SERS), by which the photonic crystal-features could enhance the optical field intensity. The on-chip separation performance of the device was confirmed by separating and detecting industrial dye (Sudan I) in an artificial aqueous mixture containing 4-mercaptobenzoic acid (MBA), where concentrated plasmonic Au colloid was casted onto the analyte spot for SERS measurement...
March 31, 2018: Materials
Josefin Sefbom, Anke Kremp, Karin Rengefors, Per R Jonsson, Conny Sjöqvist, Anna Godhe
Marine planktonic microalgae have potentially global dispersal, yet reduced gene flow has been confirmed repeatedly for several species. Over larger distances (>200 km) geographic isolation and restricted oceanographic connectivity have been recognized as instrumental in driving population divergence. Here we investigated whether similar patterns, i.e. structured populations governed by geographic isolation and/or oceanographic connectivity, can be observed at smaller (6-152 km) geographic scales. To test this we established 425 clonal cultures of the planktonic diatom Skeletonema marinoi collected from 11 locations in the Archipelago Sea (northern Baltic Sea)...
April 3, 2018: Environmental Microbiology
Nanjing Zhao, Xiaoling Zhang, Gaofang Yin, Ruifang Yang, Li Hu, Shuang Chen, Jianguo Liu, Wenqing Liu
In view of the problem of the on-line measurement of algae classification, a method of algae classification and concentration determination based on the discrete three-dimensional fluorescence spectra was studied in this work. The discrete three-dimensional fluorescence spectra of twelve common species of algae belonging to five categories were analyzed, the discrete three-dimensional standard spectra of five categories were built, and the recognition, classification and concentration prediction of algae categories were realized by the discrete three-dimensional fluorescence spectra coupled with non-negative weighted least squares linear regression analysis...
March 19, 2018: Optics Express
Emily M van Egmond, Peter M van Bodegom, Jurgen R van Hal, Richard S P van Logtestijn, Matty P Berg, Rien Aerts
Suboptimal environmental conditions are ubiquitous in nature and commonly drive the outcome of biological interactions in community processes. Despite the importance of biological interactions for community processes, knowledge on how species interactions are affected by a limiting resource, for example, low food availability, remains limited. Here, we tested whether variation in food supply causes nonadditive consumption patterns, using the macroinvertebrate community of intertidal sandy beaches as a model system...
March 2018: Ecology and Evolution
Yuliya Paukku, Zoltan Varga, Donald G Truhlar
We present a global ground-state potential energy surface (PES) for the triplet spin state of O4 that is suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation in electronically adiabatic spin-conserving O2 -O2 collisions. The surface is based on MS-CASPT2/maug-cc-pVTZ electronic structure calculations with scaled external correlation; the active space has 16 electrons in 12 orbitals. The global ground-state potential energy surface was fitted by a many-body approach with an accurate O-O pairwise interaction and a fit of the many-body interaction potential to 10 180 electronic structure data points...
March 28, 2018: Journal of Chemical Physics
Shota Tsuru, Takashi Fujikawa, Mauro Stener, Piero Decleva, Akira Yagishita
We present a new theoretical work for the ultrafast x-ray photoelectron diffraction (UXPD) method to track photodissociation of molecules over the long range in femtosecond time scale. Our theory combines the accurate multicenter description of XPD at short to medium distances and the multiple-scattering XPD approach at larger internuclear separations. Then, the theoretical framework is applied to a demonstration of the UXPD profiles from halogen diatomics undergoing photodissociation. The computational results indicate that such a combination of the two theoretical approaches sufficiently works to seamlessly track the conformational evolution during photodissociation...
March 28, 2018: Journal of Chemical Physics
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