291 research outputs found
RNA/DNA ratios as estimate of metabolic and functional traits in diatom species from the northwestern Adriatic Sea
Different phytoplankton biomass estimations can provide information about abundance variation, but they are not able to describe the metabolic activity of species or groups within assemblages. Conversely, molecular traits are key for the metabolic dynamics in pelagic ecosystems. To investigate if the RNA/DNA and taxon-specific 18S ribosomal RNA (rRNA)/ribosomal DNA (rDNA) ratios could be used to assess and be indicators of metabolic activity in marine phytoplankton species, two Adriatic diatom species, Chaetoceros socialis and Skeletonema marinoi, were studied. Significant correlations between abundance, chlorophyll a, carbon content and proteins were found in individual and co-cultured growth experiments (from r(s) = 0.570 to r(s) = 0.986, P < 0.001). The biomass trend followed a logistic curve without providing additional information regarding diatom metabolic activity. In both experiments, the RNA/DNA and taxon-specific 18S rRNA/rDNA ratios of C. socialis and S. marinoi showed maximum values at the beginning of the growth phase, i.e as 23.2 +/- 1.5 and 15.3 +/- 0.8, and 16.2 +/- 1.6 and 30.1 +/- 5.4 after 2 and 6 days, respectively, in individual cultures, with a subsequent significant decrease in these values for both species in individual and co-culture experiments. Our results showed that these molecular rRNA/rDNA ratios expressed an activation of metabolism before the abundance increases, even in the presence of interspecific interaction between C. socialis and S. marinoi
Physical interactions between marine phytoplankton and PET plastics in seawater.
Plastics are the most abundant marine debris globally dispersed in the oceans and its production is rising
with documented negative impacts in marine ecosystems. However, the chemical-physical and biological
interactions occurring between plastic and planktonic communities of different types of microorganisms
are poorly understood. In these respects, it is of paramount importance to understand, on a molecular
level on the surface, what happens to plastic fragments when dispersed in the ocean and directly
interacting with phytoplankton assemblages. This study presents a computer-aided analysis of electron
paramagnetic resonance (EPR) spectra of selected spin probes able to enter the phyoplanktonic cell
interface and interact with the plastic surface. Two different marine phytoplankton species were
analyzed, such as the diatom Skeletonema marinoi and dinoflagellate Lingulodinium polyedrum, in absence
and presence of polyethylene terephthalate (PET) fragments in synthetic seawater (ASPM), in order to insitu
characterize the interactions occurring between the microalgal cells and plastic surfaces. The analysis
was performed at increasing incubation times. The cellular growth and adhesion rates of microalgae in
batch culture medium and on the plastic fragments were also evaluated. The data agreed with the EPR
results, which showed a significant difference in terms of surface properties between the diatom and
dinoflagellate species. Low-polar interactions of lipid aggregates with the plastic surface sites were mainly responsible for the cell-plastic adhesion by S. marinoi, which is exponentially growing on the
plastic surface over the incubation time
First Finding of Ostreopsis cf. ovata Toxins in Marine Aerosols
Since the late 1990s, a respiratory syndrome has been repetitively observed in humans concomitant with Ostreopsis spp. blooms (mainly O. cf. ovata) in the Mediterranean area. Previous studies have demonstrated that O. cf. ovata produces analogues of palytoxin (ovatoxins and a putative palytoxin), one of the most potent marine toxins. On the basis of the observed association between O. cf. ovata blooms, respiratory illness in people, and detection of palytoxin complex in algal samples, toxic aerosols, containing Ostreopsis cells and/or the toxins they produce, were postulated to be the cause of human illness. A small scale monitoring study of marine aerosol carried out along the Tuscan coasts (Italy) in 2009 and 2010 is reported.
Aerosols were collected concomitantly with O. cf. ovata blooms, and they were analyzed by both PCR assays and LC-HRMS. The results, besides confirming the presence of O. cf. ovata cells, demonstrated for the first time the occurrence of ovatoxins in the aerosol at levels of 2.4 pg of ovatoxins per liter of air. Given the lack of toxicological data on palytoxins by inhalation exposure, our results are only a first step toward a more comprehensiveunderstanding of the Ostreopsis-related respiratory syndrome
Active role of the mucilage in the toxicity mechanism of the harmful benthic dinoflagellate Ostreopsis cf. ovata.
Ostreopsis cf. ovata is a harmful benthic dinoflagellate, widespread along most of the Mediterranean
coasts. It produces a wide range of palytoxin-like compounds and variable amounts of mucus that may
totally cover substrates, especially during the stationary phase of blooms. Studies on different aspects of
the biology and ecology of Ostreopsis spp. are increasing, yet knowledge on toxicity mechanism is still
limited. In particular, the potential active role of the mucilaginous matrix has not yet been shown,
although when mass mortalities have occurred, organisms have been reported to be covered by the
typical brownish mucilage. In order to better elucidate toxicity dependence on direct/indirect contact,
the role of the mucilaginous matrix and the potential differences in toxicity along the growth curve of O.
cf. ovata, we carried out a toxic bioassay during exponential, stationary and late stationary phases.
Simultaneously, a molecular assay was performed to quantify intact cells or to exclude cells presence. A
liquid chromatography – high resolution mass spectrometry (LC-HRMS) analysis was also carried out to
evaluate toxin profile and content in the different treatments. Our results report higher mortality of
model organism, especially during the late stationary phase, when direct contact between a model
organism and intact microalgal cells occurs (LC50-48h <4 cells/ml on Artemia salina). Also growth
medium devoid of microalgal cells but containing O. cf. ovata mucilage caused significant toxic effects.
This finding is also supported by chemical analysis which shows the highest toxin content in pellet
extract (95%) and around 5% of toxins in the growth medium holding mucous, while the treatment
devoid of both cells and mucilage did not contain any detectable toxins. Additionally, the connection
between mucilaginous matrix and thecal plates, pores and trychocysts was explored by way of atomic
force microscopy (AFM) to investigate the cell surface at a sub-nanometer resolution, providing a
pioneering description of cellular features
Assessment of spatio-temporal variability of faecal pollution along coastal waters during and after rainfall events.
More than 80% of wastewaters are discharged into rivers or seas, with a negative impact on
water quality along the coast due to the presence of potential pathogens of faecal origin. Escherichia
coli and enterococci are important indicators to assess, monitor, and predict microbial water quality
in natural ecosystems. During rainfall events, the amount of wastewater delivered to rivers and
coastal systems is increased dramatically. This study implements measures capable of monitoring the
pathways of wastewater discharge to rivers and the transport of faecal bacteria to the coastal area
during and following extreme rainfall events. Spatio-temporal variability of faecal microorganisms
and their relationship with environmental variables and sewage outflow in an area located in the
western Adriatic coast (Fano, Italy) was monitored. The daily monitoring during the rainy events
was carried out for two summer seasons, for a total of five sampling periods. These results highlight
that faecal microbial contaminations were related to rainy events with a high flow of wastewater,
with recovery times for the microbiological indicators varying between 24 and 72 h and influenced by
a dynamic dispersion. The positive correlation between ammonium and faecal bacteria at the Arzilla
River and the consequences in seawater can provide a theoretical basis for controlling ammonium
levels in rivers as a proxy to monitor the potential risk of bathing waters pathogen pollution
Modelling the Quality of Bathing Waters in the Adriatic Sea
The aim of this study is to develop a relocatable modelling system able to describe the
microbial contamination that affects the quality of coastal bathing waters. Pollution events are mainly
triggered by urban sewer outflows during massive rainy events, with relevant negative consequences
on the marine environment and tourism and related activities of coastal towns. A finite element
hydrodynamic model was applied to five study areas in the Adriatic Sea, which differ for urban,
oceanographic and morphological conditions. With the help of transport-diffusion and microbial
decay modules, the distribution of Escherichia coli was investigated during significant events. The
numerical investigation was supported by detailed in situ observational datasets. The model results
were evaluated against water level, sea temperature, salinity and E. coli concentrations acquired in
situ, demonstrating the capacity of the modelling suite in simulating the circulation in the coastal
areas of the Adriatic Sea, as well as several main transport and diffusion dynamics, such as riverine
and polluted waters dispersion. Moreover, the results of the simulations were used to perform a
comparative analysis among the different study sites, demonstrating that dilution and mixing, mostly
induced by the tidal action, had a stronger effect on bacteria reduction with respect to microbial
decay. Stratification and estuarine dynamics also play an important role in governing microbial
concentration. The modelling suite can be used as a beach management tool for improving protection
of public health, as required by the EU Bathing Water Directive
Five-year retrospective italian multicenter study of visceral leishmaniasis treatment
The treatment of visceral leishmaniasis (VL) is poorly standardized in Italy in spite of the existing evidence. All consecutive patients with VL admitted at 15 Italian centers as inpatients or outpatients between January 2004 and December 2008 were retrospectively considered; outcome data at 1 year after treatment were obtained for all but 1 patient. Demographic characteristics, underlying diseases, diagnostic procedures, treatment regimens and outcomes, as well as side effects were recorded. A confirmed diagnosis of VL was reported for 166 patients: 120 (72.3%) immunocompetent, 21 (12.6%) patients with immune deficiencies other than HIV infection, and 25 (15.1%) coinfected with HIV. Liposomal amphotericin B (L-AmB) was the drug almost universally used for treatment, administered to 153 (92.2%) patients. Thirty-seven different regimens, including L-AmB were used. The mean doses were 29.4 \ub1 7.9 mg/kg in immunocompetent patients, 32.9 \ub1 8.6 mg/kg in patients with non-HIV-related immunodeficiencies, and 40.8 \ub1 6.7 mg/kg in HIV-infected patients (P < 0.001). The mean numbers of infusion days were 7.8 \ub1 3.1 in immunocompetent patients, 9.6 \ub1 3.9 in non-HIV-immunodeficient patients, and 12.0 \ub1 3.4 in HIV-infected patients (P < 0.001). Mild and reversible adverse events were observed in 12.2% of cases. Responsive patients were 154 (93.3%). Successes were 98.4% among immunocompetent patients, 90.5% among non-HIV-immunodeficient patients, and 72.0% among HIV-infected patients. Among predictors of primary response to treatment, HIV infection and age held independent associations in the final multivariate models, whereas the doses and duration of L-AmB treatment were not significantly associated. Longer treatments and higher doses of L-AmB were not able to significantly modify treatment outcomes either in the immunocompetent or in the immunocompromised population
New Approach Using the Real-Time PCR Method for Estimation of the Toxic Marine Dinoflagellate Ostreopsis cf. ovata in Marine Environment
Background: We describe the development and validation of a new quantitative real time PCR (qrt-PCR) method for the
enumeration of the toxic benthic dinoflagellate Ostreopsis cf. ovata in marine environment. The benthic Ostreopsis sp. has a
world-wide distribution and is associated during high biomass proliferation with the production of potent palytoxin-like
compounds affecting human health and environment. Species-specific identification, which is relevant for the complex of
different toxins production, by traditional methods of microscopy is difficult due to the high morphological variability, and
thus different morphotypes can be easily misinterpreted.
Methodology/Findings: The method is based on the SYBR I Green real-time PCR technology and combines the use of a
plasmid standard curve with a ‘‘gold standard’’ created with pooled crude extracts from environmental samples collected
during a bloom event of Ostreopsis cf. ovata in the Mediterranean Sea. Based on their similar PCR efficiencies (95% and 98%,
respectively), the exact rDNA copy number per cell was obtained in cultured and environmental samples. Cell lysates were
used as the templates to obtain total recovery of DNA. The analytical sensitivity of the PCR was set at two rDNA copy
number and 8.061024 cell per reaction for plasmid and gold standards, respectively; the sensitivity of the assay was of cells
g21 fw or 121 in macrophyte and seawater samples, respectively. The reproducibility was determined on the total linear
quantification range of both curves confirming the accuracy of the technical set-up in the complete ranges of quantification
over time.
Conclusions/Significance: We developed a qrt-PCR assay specific, robust and high sample throughput for the absolute
quantification of the toxic dinoflagellate Ostreopsis cf. ovata in the environmental samples. This molecular approach may be
considered alternative to traditional microscopy and applied for the monitoring of benthic toxic microalgal species in the
marine ecosystems
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