1,721,001 research outputs found
USE OF THE DIFFERENTIAL DISPLAY TECHNIQUE (DD-PCR) FOR THE IDENTIFICATION OF DIFFERENTIALLY EXPRESSED GENES IN ALEXANDRIUM MINUTUM RESTING CYSTS
No full textEnhancing neutral lipid content in Skeletonema marinoi through multiple phase growth in a bench photobioreactor
Full text linkThe continuing increase in fuel demand, the dramatic situation of climate changes and global warming are bringing worldwide attention to identification of alternative energy source that can replace fossil fuel. Among all the feedstock considered for biodiesel production, microalgae are the most promising. In particular, it has been demonstrated that microalgae enhance their neutral lipids content in stress conditions, such as nutrient starvation. However, this increase in neutral lipids content is often coupled with a strong biomass decrease. In this study, in order to limit this side effect, a novel three-phase growth strategy was tested on the diatom . Skeletonema marinoi. After a first phase directed to biomass production the culture, during a second phase of semi-continuous regimen characterized with reduction of nitrate concentration, achieved a neutral lipids content per cell of 10% of dry weight with slight impact on biomass. After these two phases the cells, gradually acclimatized to low nitrogen concentration, were still able to grow in a third maturation phase performed in batch. During this last phase, the culture further increased neutral lipid content up to the 30 % of dry weight
Neutral lipid content and biomass production in Skeletonema marinoi (Bacillariophyceae) culture in response to nitrate limitation
Full text linkMicroalgae are one of the most promising biodiesel feedstocks due to their
efficiency in CO2 fixation and high neutral lipid productivity. Nutrient–stress conditions,
including nitrogen starvation, enhance neutral lipid content, but at the same time lead to a
reduction of biomass. To maximize lipid production in the diatom Skeletonema marinoi, we
investigated two different nitrogen starvation approaches. In the first experimental approach,
inocula were effectuated in modified f/2 media with decreasing nitrogen concentration,
while in the second experiment, nitrate concentration was gradually reduced through a
collection/resuspension system in which the culture was periodically collected and
resuspended in culture medium with a lower nitrate concentration. In the first approach,
the neutral lipid accumulation was accompanied by a strong biomass reduction, as was
expected, whereas the second experiment generated cultures with significantly higher
neutral lipid content without affecting biomass production. The total proteins and total
carbohydrates, which were also quantified in both experiments, suggest that in S. marinoi,
neutral lipid accumulation during nutrient starvation did not derive from a new carbon
partition of accumulated carbohydrates
Development of new procedures for the isolation of phytoplankton DNA from fixed samples
Full text linkPhytoplankton samples collected for routine monitoring programmes have traditionally been preserved with fixatives before subsequent analytical procedures such as microscope-based identification, or simply to permit transport between laboratories. In recent years, to simplify identification and enumeration, the use of DNA or RNA probes coupled with the PCR assay has progressed and now represents a routine procedure for screening cultured and field samples. However, the phytoplankton cells have often still to be treated as fixed samples.
The extraction of genomic DNA from fixed cultures of Alexandrium minutum cultures was compared using two new methods based on Magnetisable Solid Phase Support (MSPS) techniques with that using three commercial kits. Genomic DNA recovery and PCR amplification were observed and the results obtained from culture samples were validated using field samples. Among the DNA extraction techniques considered, the MSPS methods provided the best results
Application of the standard addition method for the absolute quantification of neutral lipids in microalgae using Nile red
Full text linkMicroalgae are considered one of the best candidates for biofuel production due to their high content in neutral lipids, therefore, an accurate quantification of these lipids in microalgae is fundamental for the identification of the better candidates as biodiesel source.
Nile red is a fluorescent dye widely employed for the quantification of neutral lipids in microalgae. Usually, the fluorescence intensity of the stained samples is correlated to the neutral lipid content determined with standard methods, in order to draw a standard curve and deduce the neutral lipids concentration of the unknown samples positioning their fluorescence intensity values on the curve.
Standard methods used for the neutral lipids determination are laborious and often implying solvent extraction and/or other transformation (i.e. saponification or transesterification) of the sample. These methods are also time consuming and may give rise to an underestimation of the lipid content due to variable extraction yields.
The approach described in this paper combines the standard addition method and the fluorometric staining using Nile red, avoiding the association of traditional neutral lipids quantification methods to the fluorometric determination. After optimization of instrument parameters and staining conditions, a linear correlation between the fluorescence intensity of each sample stained with the Nile red and its neutral lipids content deduced with the standard addition method was identified. The obtained curve allowed the direct determination of neutral lipids content maintaining a linearity range from 0.12 to 12 μg of neutral lipids per ml of sample, without need of pre-concentration. This curve was then used in the quantification of the neutral lipids content in culture of Skeletonema marinoi (Bacillariophyceae) at different days from the inoculum. This method was also successfully applied on Chaetoceros socialis (Bacillariophyceae) and Alexandrium minutum (Dinophyceae)
Applicazione di nuove metodiche per l’estrazione di DNA di fitoplancton da campioni fissati
No full textREAL-TIME PCR ASSAY FOR THE RAPID DETECTION AND QUANTIFICATION OF ALEXANDRIUM MINUTUM IN FIELD SAMPLES OF THE MEDITERRANEAN SEA
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Analysis of rRNA gene content in the Mediterranean dinoflagellate Alexandrium catenella and Alexandrium taylori: implications for the quantitative real-time PCR-based monitoring methods
No full text9 pages, 4 figures, 4 tables, supplementary material https://doi.org/10.1007/s10811-009-9411-3A number of species belonging to the genus Alexandrium are among the main toxic microalgae responsible for Harmful Algal Blooms (HABs). The monitoring of coastal waters for the presence of these microalgae is essential to identify correlations between cell abundances and environmental factors that regulate bloom dynamics. In the attempt to improve the monitoring sensitivity and the rapidity at which a large number of field samples can be processed, several molecular methods for the detection of genetically distinct HAB species have been developed during the last years. In particular, real-time PCR has been shown to be a powerful method for quantitative detection of HAB species in environmental samples. When a plasmid is used as a standard, the knowledge of the amount of target gene per cell is essential for the determination of the cell number in the field sample. In this study, we analyzed the rRNA gene content variability in several Alexandrium catenella and Alexandrium taylori strains isolated from the Mediterranean Sea using a real-time PCR-based approach. The rRNA gene content was also analyzed in different growth phases, from early exponential to stationary conditions. The results showed a general variability in the rRNA gene content depending on the strain and, for the species A. taylori, in relation also to the growth phase. These results should be taken into account for the application of the real-time quantitative PCR-based techniques for monitoring purposes in coastal seawatersThis work was partially supported by the EU STRATEGY project contract n. EVK3-CT-2001-00046, EU SEED project contract n. GOCE-CT-2005-003875 and EU NACBO project 500804-2 (2004)Peer reviewe
CAPTURE PROBE CONJUGATED TO PARAMAGNETIC ANNOPARTICLES FOR PURFICATION OF ALEXANDRIUM SPP DINOFLAGELLATE) DNA FROM ENVIRONMENTAL SAMPLES
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