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1.
Protist ; 170(2): 121-140, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30954839

RESUMO

With the increasing application of molecular techniques for diatom species discovery and identification, it is important both from a taxonomic as well as an ecological and applied perspective, to understand in which groups morphological species delimitation is congruent with molecular approaches, or needs reconsideration. Moreover, such studies can improve our understanding of morphological trait evolution in this important group of microalgae. In this study, we used morphometric analysis on light microscopy (LM) micrographs in SHERPA, detailed scanning electron microscopy (SEM), and cytological observations in LM to examine 70 clones belonging to eight distinct molecular lineages of the cosmopolitan terrestrial diatom Pinnularia borealis. Due to high within-lineage variation, no conclusive morphological separation in LM nor SEM could be detected. Morphological stasis due to the "low-morphology" problem or stabilizing selection, as well as parallel/convergent evolution, phenotypic plasticity and structural inheritance are discussed as potential drivers for the observations. Altogether, P. borealis is truly cryptic, in contrast to the majority of other diatom species complexes which turned out to be pseudo-cryptic following detailed morphological analysis.


Assuntos
Biodiversidade , Diatomáceas/classificação , Diatomáceas/ultraestrutura , Microscopia , Microscopia Eletrônica de Varredura
2.
Aquat Toxicol ; 208: 168-178, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30677712

RESUMO

As a newly emerging environmental contaminant, tributyl phosphate (TBP) is an additive flame retardant of high production volume that is frequently detected in biota and the environment. Despite evidence that TBP is a potential threat to marine organisms, ecotoxicology data for TBP in marine organisms at low trophic levels are scarce. In this study, the acute toxicological effect of TBP on the marine phytoplankton Phaeodactylum tricornutum was thoroughly investigated, and the possible mechanism was explored. The results showed that TBP at concentrations ≥0.2 mg L-1 significantly inhibited P. tricornutum growth in a clear dose-response manner, with 72-h EC10, EC20, EC50 and EC90 values of 0.067, 0.101, 0.219 and 0.716 mg L-1, respectively. Algal cells treated with TBP exhibited distorted shapes, ruptured cell membranes and damaged organelles, especially mitochondria. Additionally, apoptosis was triggered, followed by a decrease in mitochondrial membrane potential, indicating that cellular damage occurred during exposure. Although the activities of two antioxidant enzymes, superoxide peroxidase and catalase, were upregulated by TBP at 1.2 mg L-1, excess reactive oxygen species (ROS) and malondialdehyde still accumulated in algal cells after exposure, suggesting that the cells experienced oxidative stress. Moreover, both growth inhibition and apoptosis were positively correlated with ROS levels and were ameliorated by pretreatment with the ROS scavenger N-acetyl-l-cysteine. Taken together, the results indicate that TBP exposure leads to growth inhibition and cellular damage in P. tricornutum, and a ROS-mediated pathway might contribute to these observed toxicological effects.


Assuntos
Diatomáceas/metabolismo , Organofosfatos/toxicidade , Espécies Reativas de Oxigênio/metabolismo , Acetilcisteína/farmacologia , Apoptose/efeitos dos fármacos , Catalase/metabolismo , Diatomáceas/efeitos dos fármacos , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/ultraestrutura , Malondialdeído/metabolismo , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Fitoplâncton/efeitos dos fármacos , Superóxido Dismutase/metabolismo , Poluentes Químicos da Água/toxicidade
3.
Biochim Biophys Acta Bioenerg ; 1860(1): 41-51, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30447184

RESUMO

Diatoms show a special organisation of their plastid membranes, such that their thylakoids span the entire plastid in bands of three. While in higher plants the interaction of the light harvesting complex II and photosystem II with divalent cations (especially Mg2+) was found to take part in the interplay of electrostatic attraction and repulsion in grana membrane appression, for diatoms the key players in maintaining proper membrane distances were not identified so far. In this work, we investigated the changes in the thylakoid architecture of Thalassiosira pseudonana in reaction to different salts by using circular dichroism and fluorescence spectroscopy in combination with other techniques. We show that divalent cations have an important influence on optimal pigment organisation and thus also on maintaining membrane appression. Thereby, monovalent cations are far less effective. The concentration needed is in a physiological range and fits well with the values obtained for higher plant grana stacking, despite the fact that strict protein segregation as seen in higher plant grana is missing.


Assuntos
Cátions Bivalentes/farmacologia , Diatomáceas/ultraestrutura , Tilacoides/ultraestrutura , Dicroísmo Circular , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Plastídeos , Espectrometria de Fluorescência
4.
J Phycol ; 54(6): 918-922, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30270437

RESUMO

Pseudo-nitzschia nanaoensis sp. nov. is described from waters around Nan'ao Island (South China Sea), using morphological data and molecular evidence. This species is morphologically most similar to P. brasiliana, but differs by a denser arrangement of fibulae, interstriae, and poroids, as well as by the structure of the valvocopula and the narrow second band. Pseudo-nitzschia nanaoensis constitutes a monophyletic lineage and is well differentiated from other species on the LSU and ITS2 sequence-structure trees. Pseudo-nitzschia nanaoensis makes up the basal node on the LSU tree, and forms a sister clade with a group of P. pungens and P. multiseries on the ITS2 tree. The ability of cultured strains to produce domoic acid was assessed, including its possible induction by the presence of a copepod and brine shrimp, by liquid chromatography-tandem mass spectrometry. However, no strains showed detectable domoic acid.


Assuntos
Diatomáceas/classificação , Ácido Caínico/análogos & derivados , Toxinas Marinhas/metabolismo , China , DNA de Protozoário/análise , DNA Espaçador Ribossômico/análise , Diatomáceas/citologia , Diatomáceas/genética , Diatomáceas/ultraestrutura , Ácido Caínico/metabolismo , Filogenia
5.
Protist ; 169(4): 539-568, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30036779

RESUMO

Until now only one group of diatoms, the Bacillariaceae, was known to contain heterotrophic representatives. We show that a second group, represented by species in the genus Tursiocola, has undergone evolutionary loss of photosynthesis within the Bacillariophyta. Heterotrophy was evidenced by the presence of only apochlorotic cells in live and motile specimens. Three species of Tursiocola (T. bondei sp. nov., T. alata sp. nov., and T. gracilis sp. nov.), of which at least two are apochlorotic, are described as new to science from the skin of Florida manatees. T. ziemanii and T. varicopulifera were also observed to be apochlorotic. A new morphological feature termed a "fastigium" was observed on some Tursiocola spp. and is described as an extension of the mantle margin at the valve apex that overhangs the apex and extends towards the valve face. The presence of greatly elevated marginal ridges on the valve face of T. alata sp. nov. is a newly observed morphological character within the genus. Phylogenetic analyses using ribosomal RNA sequences indicate that Tursiocola is monophyletic, though morphological character analysis suggests paraphyly as species of the closely related Epiphalaina genus are embedded within a larger Tursiocola clade.


Assuntos
Diatomáceas/isolamento & purificação , Trichechus manatus/microbiologia , Animais , Diatomáceas/classificação , Diatomáceas/ultraestrutura , Pele/microbiologia
6.
Harmful Algae ; 76: 80-95, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29887207

RESUMO

A field study was undertaken to investigate the occurrence and toxin production of species in the diatom genus Pseudo-nitzschia in Namibian waters, in the extremely productive Benguela upwelling system. From surveys conducted on the R/V Mirabilis and the R/V !Anichab, 52 strains were morphologically determined to species level, supported by nuclear ITS rDNA data. Seven species were identified; P. australis, P. decipiens, P. dolorosa, P. fraudulenta, P. plurisecta, P. pungens var. cingulata, and the new species P. bucculenta F. Gai, C. K. Hedemand, N. Lundholm & Ø. Moestrup sp. nov. Molecular and morphological diversity of the Namibian Pseudo-nitzschia species is discussed. Most importantly, P. bucculenta is both morphologically and phylogenetically most similar to P. dolorosa differing mainly in valve width and densities of striae, poroids and band striae as well as by four hemi-compensatory base changes in the ITS2. Morphological and molecular differences among the strains of P. decipiens suggest a temperate and a warm water subdivision. The geographical and toxigenic characteristics of the identified Pseudo-nitzschia species are described and compared to previous studies. Initial tests of toxin production in all seven species revealed production of domoic acid (DA) in two species: one strain of P. australis (0.074 pg DA cell-1) and two strains of P. plurisecta (0.338 pg DA cell-1 and 0.385 pg DA cell-1).


Assuntos
Diatomáceas/classificação , DNA de Algas/análise , DNA Espaçador Ribossômico/análise , Diatomáceas/química , Diatomáceas/genética , Diatomáceas/ultraestrutura , Toxinas Marinhas , Microscopia Eletrônica de Transmissão , Namíbia
7.
J Phycol ; 54(4): 557-570, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29908074

RESUMO

Some diatoms are able to colonize as epibionts on their potential zooplankton predators. Here, we report Pseudohimantidium pacificum living on the copepod Corycaeus giesbrechti and as a new finding on Oithona nana, Protoraphis atlantica living on the copepod Pontellopsis brevis, Protoraphis hustedtiana on the cypris larvae of barnacles, and Falcula hyalina on the copepod Acartia lilljeborgii. The epizoic diatoms were able to grow as free-living forms under culture conditions. Pseudohimantidium pacificum and P. atlantica appeared as the most derived species from their benthic diatom ancestors. The mucilage pad or stalk of the strains of these species showed important morphological distinction when compared with their epizoic forms. Barnacle larvae explore benthic habitats before settlement, and epibiosis on them is an example where P. hustedtiana profits from the host behavior for dispersal of its benthic populations. Molecular phylogenies based on the SSU rRNA and RuBisCO large subunit (rbcL) gene sequences revealed F. hyalina as an independent lineage within the Fragilariales (Tabularia, Catacombas, and others), consistent with its morphological distinction in the low number of rows (≤6) in the ocellulimbus, among other features. We propose the transfer of F. hyalina to the genus Pseudofalcula gen. nov. Molecular phylogeny suggests a single order for the members of the Cyclophorales and the Protoraphidales, and that the epibioses of araphid diatoms on marine zooplankton have been independently acquired several times. These clades are constituted of both epizoic and epiphytic/epilithic forms that evidence a recent acquisition of the epizoic modus vivendi.


Assuntos
Diatomáceas/classificação , Zooplâncton/classificação , Animais , DNA Ribossômico/análise , Diatomáceas/citologia , Diatomáceas/genética , Diatomáceas/ultraestrutura , Microscopia Eletrônica de Varredura , Filogenia , Fitoplâncton/classificação , Fitoplâncton/citologia , Fitoplâncton/genética , Fitoplâncton/ultraestrutura , Ribulose-Bifosfato Carboxilase/análise , Zooplâncton/citologia , Zooplâncton/genética , Zooplâncton/ultraestrutura
8.
PLoS One ; 13(6): e0196744, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29883488

RESUMO

The diatom Phaeodactylum tricornutum has been used as a model for cell biologists and ecologists for over a century. We have incorporated several new raphid pennates into a three gene phylogenetic dataset (SSU, rbcL, psbC), and recover Gomphonemopsis sp. as sister to P. tricornutum with 100% BS support. This is the first time a close relative has been identified for P. tricornutum with robust statistical support. We test and reject a succession of hypotheses for other relatives. Our molecular data are statistically significantly incongruent with placement of either or both species among the Cymbellales, an order of diatoms with which both have been associated. We believe that further resolution of the phylogenetic position of P. tricornutum will rely more on increased taxon sampling than increased genetic sampling. Gomphonemopsis is a benthic diatom, and its phylogenetic relationship with P. tricornutum is congruent with the hypothesis that P. tricornutum is a benthic diatom with specific adaptations that lead to active recruitment into the plankton. We hypothesize that other benthic diatoms are likely to have similar adaptations and are not merely passively recruited into the plankton.


Assuntos
Bases de Dados de Ácidos Nucleicos , Diatomáceas/classificação , Diatomáceas/genética , Filogenia , Fitoplâncton/genética , Diatomáceas/ultraestrutura , Fitoplâncton/ultraestrutura
9.
Appl Microbiol Biotechnol ; 102(14): 5889-5899, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29802480

RESUMO

The intricate patterning of diatom silica frustules at nanometer-to-micrometer scales makes them of interest for a wide range of industrial applications. For some of these applications, a specific size range in nanostructure is required and may be achieved by selecting species with the desired properties. However, as all biological materials, diatom frustules exhibit variability in their morphological parameters and this variability can to some extent be affected and controlled by environmental conditions. In this review, we explore the effects of different environmental factors including salinity, heavy metals, temperature, pH, extracellular Si(OH)4 or Ge(OH)4 concentration, light regime, UV irradiance, long-term cultivation, and biotic factors on the nanostructure of diatom frustules. This compilation of studies illustrates that it is possible to affect the nanostructure of diatom frustules in vivo by controlling different environmental factors as well as by direct chemical modification of frustules. We compare these methods and present examples of how these changes affect the range of variability as well as comparing the magnitude of size changes of the most promising methods.


Assuntos
Diatomáceas/ultraestrutura , Meio Ambiente , Diatomáceas/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Dióxido de Silício/química
10.
Harmful Algae ; 75: 118-128, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29778221

RESUMO

The Benguela upwelling system, considered the world's most productive marine ecosystem, has a long record of potentially toxic diatoms belonging to the genus Pseudo-nitzschia. Species of Pseudo-nitzschia were reported as early as 1936 from the northern Benguela upwelling system (nBUS). For the current study, long-term phytoplankton monitoring data (2004-2011) for the Namibian coast were analysed to examine inshore and offshore temporal distribution of Pseudo-nitzschia species, their diversity and ultrastructure. The potentially toxigenic P. pungens and P. australis were the dominant inshore species, whereas offshore Pseudo-nitzschia showed a higher diversity that also included potentially toxic species. During a warming event, a community shift from P. pungens and P. australis dominance to P. fraudulenta and P. multiseries was documented in the central nBUS. A case study of a toxic event (August 2004) revealed that P. australis and P. pungens were present at multiple inshore and offshore stations, coincident with fish (pilchard) and bird mortalities reported from the central part of Namibia. Toxin analyses (LC-MS/MS) of samples collected from June to August 2004 revealed the presence of particulate domoic acid (DA) in seawater at multiple stations (maximum ∼180 ng DA/L) in the >0.45 µm size-fraction, as well as detectable DA (0.12 µg DA/g) in the gut of one of two pilchard samples tested. These findings indicate that DA may have been associated with the fish and bird mortalities reported from this event in the nBUS. However, the co-occurrence of very high biomass phytoplankton blooms suggests that other explanations may be possible.


Assuntos
Diatomáceas/química , Ácido Caínico/análogos & derivados , Toxinas Marinhas/análise , Oceano Atlântico , Biodiversidade , Cromatografia Líquida , Diatomáceas/classificação , Diatomáceas/ultraestrutura , Ácido Caínico/análise , Microscopia Eletrônica de Transmissão , Namíbia , Fitoplâncton/química , Fitoplâncton/classificação , Fitoplâncton/ultraestrutura , Espectrometria de Massas em Tandem
11.
Int J Mol Sci ; 19(5)2018 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-29748514

RESUMO

The use of natural products (NPs) as possible alternative biocidal compounds for use in antifouling coatings has been the focus of research over the past decades. Despite the importance of this field, the efficacy of a given NP against biofilm (mainly bacteria and diatoms) formation is tested with the NP being in solution, while almost no studies test the effect of an NP once incorporated into a coating system. The development of a novel bioassay to assess the activity of NP-containing and biocide-containing coatings against marine biofilm formation has been achieved using a high-throughput microplate reader and highly sensitive confocal laser scanning microscopy (CLSM), as well as nucleic acid staining. Juglone, an isolated NP that has previously shown efficacy against bacterial attachment, was incorporated into a simple coating matrix. Biofilm formation over 48 h was assessed and compared against coatings containing the NP and the commonly used booster biocide, cuprous oxide. Leaching of the NP from the coating was quantified at two time points, 24 h and 48 h, showing evidence of both juglone and cuprous oxide being released. Results from the microplate reader showed that the NP coatings exhibited antifouling efficacy, significantly inhibiting biofilm formation when compared to the control coatings, while NP coatings and the cuprous oxide coatings performed equally well. CLSM results and COMSTAT analysis on biofilm 3D morphology showed comparable results when the NP coatings were tested against the controls, with higher biofilm biovolume and maximum thickness being found on the controls. This new method proved to be repeatable and insightful and we believe it is applicable in antifouling and other numerous applications where interactions between biofilm formation and surfaces is of interest.


Assuntos
Bactérias/efeitos dos fármacos , Biofilmes/efeitos dos fármacos , Produtos Biológicos/química , Diatomáceas/efeitos dos fármacos , Bactérias/ultraestrutura , Diatomáceas/ultraestrutura , Desinfetantes/química , Ensaios de Triagem em Larga Escala , Microscopia Confocal
12.
New Phytol ; 219(1): 122-134, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29672846

RESUMO

The optical properties of diatom silicate frustules inspire photonics and nanotechnology research. Whether light interaction with the nano-structure of the frustule also affects diatom photosynthesis has remained unclear due to lack of information on frustule optical properties under more natural conditions. Here we demonstrate that the optical properties of the frustule valves in water affect light harvesting and photosynthesis in live cells of centric diatoms (Coscinodiscus granii). Microscale cellular mapping of photosynthesis around localized spot illumination demonstrated optical coupling of chloroplasts to the valve wall. Photonic structures of the three-layered C. granii valve facilitated light redistribution and efficient photosynthesis in cell regions distant from the directly illuminated area. The different porous structure of the two sides of the valve exhibited photon trapping and forward scattering of blue light enhancing photosynthetic active radiation inside the cell. Photonic structures of diatom frustules thus alter the cellular light field with implications on diatom photobiology.


Assuntos
Diatomáceas/fisiologia , Nanoestruturas/ultraestrutura , Fotobiologia , Fotossíntese/fisiologia , Silicatos/metabolismo , Cloroplastos/metabolismo , Diatomáceas/química , Diatomáceas/efeitos da radiação , Diatomáceas/ultraestrutura , Luz , Microscopia Eletrônica de Varredura , Nanoestruturas/efeitos da radiação , Nanotecnologia , Óptica e Fotônica
13.
Nat Commun ; 9(1): 953, 2018 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-29507291

RESUMO

Diatoms are one of the major primary producers in the ocean, responsible annually for ~20% of photosynthetically fixed CO2 on Earth. In oceanic models, they are typically represented as large (>20 µm) microphytoplankton. However, many diatoms belong to the nanophytoplankton (2-20 µm) and a few species even overlap with the picoplanktonic size-class (<2 µm). Due to their minute size and difficulty of detection they are poorly characterized. Here we describe a massive spring bloom of the smallest known diatom (Minidiscus) in the northwestern Mediterranean Sea. Analysis of Tara Oceans data, together with literature review, reveal a general oversight of the significance of these small diatoms at the global scale. We further evidence that they can reach the seafloor at high sinking rates, implying the need to revise our classical binary vision of pico- and nanoplanktonic cells fueling the microbial loop, while only microphytoplankton sustain secondary trophic levels and carbon export.


Assuntos
Carbono/metabolismo , Diatomáceas/fisiologia , Fitoplâncton/fisiologia , Estações do Ano , Biomassa , Contagem de Células , Clorofila/metabolismo , Código de Barras de DNA Taxonômico , Diatomáceas/ultraestrutura , Geografia , Sedimentos Geológicos , Mar Mediterrâneo , Fitoplâncton/classificação , Fitoplâncton/ultraestrutura
14.
Environ Toxicol Pharmacol ; 59: 152-162, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29597078

RESUMO

In recent years, there have been significant advances in the knowledge and understanding of the pollution attributed to effects of aquatic toxic metals on fresh water benthic diatoms. In this study, the cell growth, chlorophyll a content and superoxide dismutase activity in Halamphora veneta (Kützing) Levkov and Surirella crumena Brébisson exposed to cadmium and lead, were investigated. Furthermore, in order to explore the potential function of H. veneta on environmental monitoring and environmental remediation, expression of two genes (psbA, psaB) and morphological analysis of H. veneta were carried out. The cells growth of H. veneta and S. crumena were generally inhibited with cadmium and lead exposure during 96 h, while cells density of H. veneta was significantly increased under the low concentration at 24 h cadmium exposure. Our results indicated that H. veneta had a certain tolerance to toxic metals at initial treated time. In addition, the significantly changes of chlorophyll a content and SOD activities in H. veneta and S. crumena indicated that both photosynthetic system and the antioxidant system in benthic diatom might play important roles on the toxic metals tolerant mechanism. Meanwhile, it can be confirmed that the diatom photosynthetic systems play roles on toxic metals resistance inferred from the gene expression of psbA and psaB in H. veneta. Finally, the results of scanning electron microscopy showed that there was a slightly deformation on cells following the cadmium exposure in H. veneta, while obvious deformation with cell greatly widened after lead exposure. The present work will be helpful to understand the effect mechanisms of toxic metal by comparing two kinds of diatom on cell inhibition, biological response and morphological changes, which will provide more information for possible use of benthic diatoms in bioremediation.


Assuntos
Cádmio/toxicidade , Diatomáceas/efeitos dos fármacos , Chumbo/toxicidade , Poluentes Químicos da Água/toxicidade , Clorofila/metabolismo , Clorofila A , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/metabolismo , Diatomáceas/ultraestrutura , Regulação da Expressão Gênica/efeitos dos fármacos , Microscopia Eletrônica de Varredura , Fotossíntese/genética , Superóxido Dismutase/metabolismo
15.
J Phycol ; 54(2): 275-298, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29419886

RESUMO

The diatom genus Entomoneis is known from the benthos and plankton of marine, brackish, and freshwaters. Entomoneis includes diatoms with a bilobate keel elevated above the valve surface, a sigmoid canal raphe, and numerous girdle bands. Owing mostly to the scarcity of molecular data for a diverse set of species, the phylogeny of Entomoneis has not been investigated in depth. The few previous studies that included Entomoneis were focused on broader questions and the available data were from a small number of either unidentified Entomoneis or well-known species (e.g., E. paludosa). Since the first description of new species combining both molecular and morphological characters (E. tenera), we have continued to cultivate and investigate Entomoneis in the plankton of the Adriatic Sea. Combined multigene phylogeny (SSU rDNA sequences, rbcL, and psbC genes) and morphological observations (LM, SEM and TEM) revealed six new Entomoneis species supported by phylogenetic and morphological data: E. pusilla, E. gracilis, E. vilicicii, E. infula, E. adriatica, and E. umbratica. The most important morphological features for species delineation were cell shape, the degree and mode of torsion, valve apices, the appearance and structure of the transition between keel and valve body, the ultrastructure and the shape of the girdle bands, and the arrangement and density of perforations along the valve and valvocopulae. Our results highlight the underappreciated diversity of Entomoneis and call for a more in-depth morphological and molecular investigation of this genus especially in planktonic habitats.


Assuntos
Diatomáceas/classificação , Diatomáceas/citologia , Proteínas de Algas/análise , Croácia , DNA de Algas/análise , DNA Ribossômico/análise , Diatomáceas/genética , Diatomáceas/ultraestrutura , Mar Mediterrâneo , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Filogenia
17.
Colloids Surf B Biointerfaces ; 162: 220-227, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29190473

RESUMO

Antifouling function of copper-based layers is usually gained through the release of cuprous or copper ions to damage most fouling species. In this research the intervening mechanisms of copper ions in formation of simplified conditioning layer comprising marine polysaccharide alginate and subsequent adhesion of typical marine bacteria and algae were studied. Fast interaction of Cu2+ with alginate with the formation of copper alginate multimers was observed for the first time by negative-staining electron microscopy. Interconnecting chains of alginate and copper alginate upon adsorption on silicon wafer and tangled structure of the conditioning layer were further characterized by atomic force microscopy. Adhesion testing showed that consumption of copper ions by their linking with alginate in incubation solutions resulted in mitigated toxicity of the ions to the microorganisms Bacillus sp., Chlorella pyrenoidosa and Phaeodactylum tricornutum. The results would give insight into understanding and regulating the formation of conditioning layer for desired antifouling performances.


Assuntos
Alginatos/química , Anti-Infecciosos/farmacologia , Incrustação Biológica/prevenção & controle , Cobre/farmacologia , Adsorção , Anti-Infecciosos/química , Bacillus/efeitos dos fármacos , Bacillus/crescimento & desenvolvimento , Bacillus/ultraestrutura , Aderência Bacteriana/efeitos dos fármacos , Chlorella/efeitos dos fármacos , Chlorella/crescimento & desenvolvimento , Chlorella/ultraestrutura , Cobre/química , Diatomáceas/efeitos dos fármacos , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/ultraestrutura , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Silício/química
18.
Protoplasma ; 255(3): 911-921, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29270874

RESUMO

Diatoms stand out among other microalgae due to the high diversity of species-specific silica frustules whose components (valves and girdle bands) are formed within the cell in special organelles called silica deposition vesicles (SDVs). Research on cell structure and morphogenesis of frustule elements in diatoms of different taxonomic groups has been carried out since the 1950s but is still relevant today. Here, cytological features and valve morphogenesis in the freshwater raphid pennate diatom Encyonema ventricosum (Agardh) Grunow have been studied using light and transmission electron microscopy of cleaned frustules and ultrathin sections of cells, and scanning electron and atomic force microscopy of the frustule surface. Data have been obtained on chloroplast structure: the pyrenoid is spherical, penetrated by a lamella (a stack of two thylakoids); the girdle lamella consists of several short lamellae. The basic stages of frustule morphogenesis characteristic of raphid pennate diatoms have been traced, with the presence of cytoskeletal elements near SDVs being observed throughout this process. Degradation of the plasmalemma and silicalemma is shown to take place when the newly formed valve is released into the space between sister cells. The role of vesicular transport and exocytosis in the gliding of pennate diatoms is discussed.


Assuntos
Diatomáceas/citologia , Diatomáceas/crescimento & desenvolvimento , Morfogênese , Cloroplastos/metabolismo , Cloroplastos/ultraestrutura , Diatomáceas/ultraestrutura , Mucilagem Vegetal/metabolismo
19.
J Tissue Eng Regen Med ; 12(1): 89-97, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-27925440

RESUMO

Many studies have highlighted the role of silicon in human bone formation and maintenance. Silicon, in fact, is considered to nucleate the precipitation of hydroxyapatite and to reduce the bone resorption. For this reason, we have combined silk fibroin (SF) with silicon-releasing diatom particles (DPs), as potential material for bone tissue engineering applications. Sponges of fibroin loaded with different amounts and sizes of DPs were prepared by solvent casting-particulate leaching method, and their morphology, porosity and mechanical properties were evaluated. The biological effect of diatom addition was assessed on human osteosarcoma cell line MG63, a suitable osteoblast-like model, through cell adhesion, metabolic activity and proliferation assays. In addition, alkaline phosphatase activity, osterix and collagen type I production in MG63 cell line were assessed as markers of early bone formation to demonstrate a pro-mineralization potential of scaffolds. Results of the studies showed that addition to fibroin of diatoms particles improved the osteogenic properties of osteoblast-like cells compared with the pure SF. Copyright © 2016 John Wiley & Sons, Ltd.


Assuntos
Materiais Biocompatíveis/farmacologia , Osso e Ossos/fisiologia , Diatomáceas/química , Fibroínas/farmacologia , Engenharia Tecidual/métodos , Fosfatase Alcalina/metabolismo , Osso e Ossos/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Diatomáceas/ultraestrutura , Módulo de Elasticidade , Humanos , Tecidos Suporte/química
20.
Molecules ; 22(12)2017 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-29258162

RESUMO

Diatom biosilica may offer an interesting perspective in the search for sustainable solutions meeting the high demand for heterogeneous catalysts. Diatomaceous earth (diatomite), i.e., fossilized diatoms, is already used as adsorbent and carrier material. While diatomite is abundant and inexpensive, freshly harvested and cleaned diatom cell walls have other advantages, with respect to purity and uniformity. The present paper demonstrates an approach to modify diatoms both in vivo and in vitro to produce a porous aluminosilicate that is serving as a potential source for sustainable catalyst production. The obtained material was characterized at various processing stages with respect to morphology, elemental composition, surface area, and acidity. The cell walls appeared normal without morphological changes, while their aluminum content was raised from the molar ratio n(Al):n(Si) 1:600 up to 1:50. A specific surface area of 55 m²/g was measured. The acidity of the material increased from 149 to 320 µmol NH3/g by ion exchange, as determined by NH3 TPD. Finally, the biosilica was examined by an acid catalyzed test reaction, the alkylation of benzene. While the cleaned cell walls did not catalyze the reaction at all, and the ion exchanged material was catalytically active. This demonstrates that modified biosilica does indeed has potential as a basis for future catalytically active materials.


Assuntos
Silicatos de Alumínio/metabolismo , Diatomáceas/metabolismo , Biocatálise , Reatores Biológicos , Diatomáceas/ultraestrutura
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