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1.
Sci Rep ; 9(1): 15892, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31664048

RESUMO

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

2.
Harmful Algae ; 86: 10-19, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31358269

RESUMO

Lyngbya majuscula is a marine filamentous cyanobacteria belonging to the family Oscillatoriaceae. Recent phylogenetic analyses of L. majuscula have reclassified a subset of this species into various genera such as Moorea, Okeania and Dapis. From the genus Moorea, Moorea producens is a toxic invasive cyanobacterium that produces bioactive secondary metabolites that can cause severe inflammation and blistering. Despite the global distribution of M. producens, little information is available on their origin, patterns of dispersal and population structure. In this study, the spatial population structure of M. producens was investigated using near-complete 16S rRNA sequences. Analysis of the global population of M. producens by Isolation by Distance and STRUCTURE revealed two significantly distinct cosmopolitan populations that were separated by a genetic break. Lineage-specific divergence estimates of 147 cyanobacterial taxa, based on a relaxed molecular clock indicated the first global emergence of M. producens during the Mesoarchean and a subsequent global recolonization during the Mesoproterozoic period. We conclude that the genetic discontinuity between both cosmopolitan populations is attributed to refugia associated with Proterozoic glacial cycles.


Assuntos
Cianobactérias , Filogenia , Filogeografia , RNA Ribossômico 16S
3.
Anal Chim Acta ; 1066: 121-130, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31027526

RESUMO

A visual, rapid, and sensitive method for the detection of two algal metabolites, geosmin (GSM) and 2-methylisoborneol (2-MIB) using a competitive displacement technique based on molecular imprinted polymers (MIPs) and fluorescent tags was developed. In this method, fluorescent tags that bind to synthetic receptor sites of MIPs were designed and synthesised. In the presence of target analytes (geosmin and 2-methylisoborneol respectively), the tags are displaced leading to fluorescence signals. The MIPs were derived from the polymerisation of functional monomers and crosslinkers in the presence of suitable templates. Good to high binding capacities and selectivities were obtained with the MIPs. The displacement of fluorescent-tagged substrates from the respective MIPs by the target analytes enabled the quantitative detection of geosmin at concentrations as low as 0.38 µM (69 µg L-1), while the LOD for 2-methylisoborneol is 0.29 µM (48 µg L-1) without any cross-reactivity, non-specific (false-positive) binding, and matrix complications. Qualitative detection of geosmin and 2-methylisoborneol is also possible via visualisation of fluorescence using a hand held UV lamp, with LOD for geosmin and 2-methylisoborneol at 0.44 µM (80 µg L-1) and 0.35 µM (60 µg L-1), respectively. The sensitivity of the system can be improved with a pre-concentration step using the respective MIPs as a sorbent.


Assuntos
/análise , Clorófitas/química , Fluorescência , Impressão Molecular , Naftóis/análise , Polímeros/química , /metabolismo , Clorófitas/metabolismo , Cinética , Estrutura Molecular , Naftóis/metabolismo , Tamanho da Partícula , Polímeros/síntese química , Propriedades de Superfície
4.
Sci Total Environ ; 655: 313-320, 2019 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-30471599

RESUMO

Plastic waste is a global issue of an increasing concern in aquatic ecosystems. Microplastics form a large proportion of plastic pollution in marine environments. Although microplastics are prevalent, their distribution along the coasts of tropical regions is not well studied. Microplastic pieces (1-5 mm) were collected from two distinct regions along the coastlines of Singapore, from the northern coast in the Johor Strait and the southern coast in the Singapore Strait. Microplastics were present in concentrations ranging from 9.20-59.9 particles per kg of dry sand sediment. The majority of microplastics identified were foam particles (55%) and fragments (35%). Microplastics were significantly more abundant on heavily populated beaches compared to pristine beaches. High throughput sequencing was used to profile the communities of bacteria on the surfaces of microplastic particles. The structure of the microbial communities was primarily characterised by Proteobacteria and Bacteroidetes and were distinct across sites. Hydrocarbon-degrading genera such as Erythrobacter were dominant in areas with heavy shipping and pollution. Potential pathogenic genera such as Vibrio and Pseudomonas were also identified. This study highlights the diverse bacterial assemblages present on marine microplastic surfaces and the importance of understanding the bacterial plastisphere.


Assuntos
Bactérias/classificação , Monitoramento Ambiental/métodos , Sedimentos Geológicos/microbiologia , Plásticos/análise , Clima Tropical , Poluentes Químicos da Água/análise , Bactérias/crescimento & desenvolvimento , Ecossistema , Sedimentos Geológicos/química , Microbiota , Singapura
5.
Sci Rep ; 8(1): 8843, 2018 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-29891968

RESUMO

Environmental DNA (eDNA) metabarcoding can greatly enhance our understanding of global biodiversity and our ability to detect rare or cryptic species. However, sampling effort must be considered when interpreting results from these surveys. We explored how sampling effort influenced biodiversity patterns and nonindigenous species (NIS) detection in an eDNA metabarcoding survey of four commercial ports. Overall, we captured sequences from 18 metazoan phyla with minimal differences in taxonomic coverage between 18 S and COI primer sets. While community dissimilarity patterns were consistent across primers and sampling effort, richness patterns were not, suggesting that richness estimates are extremely sensitive to primer choice and sampling effort. The survey detected 64 potential NIS, with COI identifying more known NIS from port checklists but 18 S identifying more operational taxonomic units shared between three or more ports that represent un-recorded potential NIS. Overall, we conclude that eDNA metabarcoding surveys can reveal global similarity patterns among ports across a broad array of taxa and can also detect potential NIS in these key habitats. However, richness estimates and species assignments require caution. Based on results of this study, we make several recommendations for port eDNA sampling design and suggest several areas for future research.


Assuntos
Biodiversidade , Código de Barras de DNA Taxonômico/métodos , DNA/genética , DNA/isolamento & purificação , Meio Ambiente , Metagenômica/métodos , Animais , Complexo IV da Cadeia de Transporte de Elétrons/genética , RNA Ribossômico 18S/genética
6.
J Phycol ; 54(2): 234-248, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29377161

RESUMO

Analyses of the mitochondrial cox1, the nuclear-encoded large subunit (LSU), and the internal transcribed spacer 2 (ITS2) RNA coding region of Pseudo-nitzschia revealed that the P. pseudodelicatissima complex can be phylogenetically grouped into three distinct clades (Groups I-III), while the P. delicatissima complex forms another distinct clade (Group IV) in both the LSU and ITS2 phylogenetic trees. It was elucidated that comprehensive taxon sampling (sampling of sequences), selection of appropriate target genes and outgroup, and alignment strategies influenced the phylogenetic accuracy. Based on the genetic divergence, ITS2 resulted in the most resolved trees, followed by cox1 and LSU. The morphological characters available for Pseudo-nitzschia, although limited in number, were overall in agreement with the phylogenies when mapped onto the ITS2 tree. Information on the presence/absence of a central nodule, number of rows of poroids in each stria, and of sectors dividing the poroids mapped onto the ITS2 tree revealed the evolution of the recently diverged species. The morphologically based species complexes showed evolutionary relevance in agreement with molecular phylogeny inferred from ITS2 sequence-structure data. The data set of the hypervariable region of ITS2 improved the phylogenetic inference compared to the cox1 and LSU data sets. The taxonomic status of P. cuspidata and P. pseudodelicatissima requires further elucidation.


Assuntos
Diatomáceas/classificação , Filogenia , Proteínas de Algas/análise , DNA Espaçador Ribossômico/análise , Diatomáceas/genética , Complexo IV da Cadeia de Transporte de Elétrons/análise , Genes de RNAr , RNA de Algas/análise , Análise de Sequência de DNA , Análise de Sequência de RNA
7.
Toxicon ; 48(6): 683-9, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16997341

RESUMO

The protein and total toxin of dinoflagellate Alexandrium tamarense at the exponential growth phase were studied at four N:P supply ratios=8, 16, 24 and 48 by maintaining the N concentration at 880 microM with variable P concentrations without nutrient limitation. Because A. tamarense grew well at all N:P supply ratios, they might synthesize RNA which contains high phosphorus and consequently low N:P atomic ratio of cells might be retained during exponential growth phase. Cellular protein:C ratio and toxin:C ratio depended on N:P supply ratio, suggesting that intracellular biochemical composition of A. tamarense might vary due to N:P supply conditions. These biochemical changes could not be detected by only investigations of cellular N:C atomic ratio which was independent on N:P supply ratio. Total cellular toxin contents of A. tamarense increased with increasing N:P supply ratio, indicated that total cellular toxin contents of A. tamarense might be stimulated by relative P-deficiency. In situ P concentration of the Seto Inland Sea of Japan has been reduced since 1980s the environmental regulation issued by Japanese Government, and therefore N:P supply ratio of input water from adjacent rivers has became higher than the Redfield ratio. The present study may suggest that the reduction of P supply into ambient sea water might cause A. tamarense to accumulate more toxin within the cell, in result, noxious A. tamarense would be more influential to marine organisms in coastal ecosystem.


Assuntos
Dinoflagelados/metabolismo , Toxinas Marinhas/metabolismo , Nitrogênio/metabolismo , Fósforo/metabolismo , Proteínas de Protozoários/metabolismo , Animais , Dinoflagelados/química , Dinoflagelados/crescimento & desenvolvimento , Ecossistema , Toxinas Marinhas/análise , Proteínas de Protozoários/análise
8.
Toxicon ; 43(4): 407-15, 2004 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-15051404

RESUMO

Nitrogen (N) supply in pulses was simulated by exposing Alexandrium tamarense which was acclimatized at low N concentration (6 microM-N) to sudden increase in concentrations of nitrate, ammonium and urea, and the variability in toxicity due to nutrient status of A. tamarense was examined. The toxin composition did not vary dramatically among the three N sources, however, ammonium induced the highest concentration of intracellular toxin, followed by urea and then nitrate. Therefore, populations utilizing high ammonium concentration could be more toxic than those growing on nitrate or urea. The toxin content was dependent on the cellular N status of nitrate grown cells only, suggesting that the competition for N in toxin production with other metabolic pathways such as growth may be different among N sources. The relationship between toxin and nutrient status is a complex interaction and it involves the redistribution of cellular N within the cells. Understanding the toxin dynamics of natural populations in relation to nutrient is essential for the mitigation of harmful dinoflagellates in a given coastal ecosystem.


Assuntos
Dinoflagelados/metabolismo , Toxinas Marinhas/toxicidade , Compostos de Nitrogênio/metabolismo , Saxitoxina/análogos & derivados , Saxitoxina/toxicidade , Animais , Carbono , Cromatografia Líquida de Alta Pressão , Dinoflagelados/química , Dinoflagelados/crescimento & desenvolvimento , Japão , Toxinas Marinhas/isolamento & purificação , Toxinas Marinhas/metabolismo , Nitratos , Compostos de Amônio Quaternário , Saxitoxina/isolamento & purificação , Saxitoxina/metabolismo , Água do Mar/análise , Ureia
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