5 research outputs found
Bioavailabilty of different forms of dissolved silica can affect marine diatom growth
No full textIn this study, we demonstrate that dissolved silica obtained from mineral (crystalline
quartz), biogenic amorphous (diatomaceous earth) and artificial amorphous
sources (Aerosil) influence the growth rate of two marine diatoms,
Chaetoceros sp. and Skeletonema marinoi. Diatoms were reared in four different
experimental conditions in artificial seawater containing either dissolved silica
previously obtained through dissolution of the mineral crystalline quartz or
two amorphous substrates, biogenic diatomaceous earth or artificial Aerosil silica.
Sodium metasilicate was used as control. When the silica in the different
media reached concentrations higher than 107 lM, particles were eliminated by
filtration and the diatom cells were inoculated. Maximum cell density, growth
and silica assimilation rates of both species in the presence of dissolved silica
derived from crystalline quartz and metasilicate were higher than those
obtained with the other silica sources. These results are discussed against the
background of previous geochemical studies that have shown that silica–water
interactions are strictly dependent on the silica polymorphs involved and on
the ionic composition of the solution. Our results demonstrate that the soluble
silicon compounds generated in seawater by crystalline sources are highly bioavailable
compared with those generated by biogenic and amorphous materials.
These findings are potentially of considerable ecological importance and may
contribute to clarifying anomalous spatial and temporal distributions of siliceous
organisms with respect to the presence of lithogenic or biogenic silica
sources in marine environments
Genome complexity of harmful microalgae
No full textDuring the past decade, next generation sequencing (NGS) technologies have provided new insights into the diversity, dynamics, and metabolic pathways of natural microbial communities. But, these new techniques face challenges related to the genome size and level of genome complexity of the species under investigation. Moreover, the coverage depth and the short-read length achieved by NGS based approaches also represent a major challenge for assembly. These factors could limit the use of these high-throughput sequencing methods for species lacking a reference genome and characterized by a high level of complexity. In the present work, the evolutionary history, mainly consisting of gene transfer events from bacteria and unicellular eukaryotes to microalgae, including harmful species, is discussed and reviewed as it relates to NGS application in microbial communities, with a particular focus on harmful algal bloom species and dinoflagellates. In the context of genetic population studies, genotyping-by-sequencing (GBS), an NGS based approach, could be used for the discovery and analysis of single nucleotide polymorphisms (SNPs). The NGS technologies are still relatively new and require further improvement. Specifically, there is a need to develop and standardize tools and approaches to handle large data sets, which have to be used for the majority of HAB species characterized by evolutionary highly dynamic genomes
Paralytic Shellfish Poisoning toxins from Mediterranean Alexandrium minutum and A. catenella: toxin profile and sxt gene content
No full textParalytic shellfish poisoning (PSP) toxins are potent water-soluble neurotoxins including the parent compound saxitoxin (STX) and a number of its congeners. They are tetrahydropurine derivatives that can be subdivided into three main groups according to substitution of the side chain: carbamoyl-, N-sulfocarbamoyl-, and decarbamoyl-toxins. The carbamoyl derivatives (STX, NEO and GTX1-4) are reported to be the most potent. Due to their accumulation in filter feeding shellfish, PSP toxins can move through the food chain inducing a toxic syndrome in seafood consumers. Symptoms are neurological with rapid onset (30-60 min from ingestion) and include paraesthesia, vertigo, numbness, tingling of the face, tongue, and lip, ataxia, blocking of respiration and even death.
Due to the high risk posed to human health by PSP toxins, a multidisciplinary integrated approach based on liquid chromatography high resolution mass spectrometry (LC-HRMS and MS2) and qPCR-based assay has been used to depict the PSP toxin scenario in the Mediterranean Sea. As the sxtA and the sxtG genes are known as the starting genes of PSP toxin synthesis in dinoflagellates, different populations of the Mediterranean A. minutum from NW Adriatic, Ionian, Tyrrhenian and Catalan Seas were grown in culture and analyzed by qPCR in order to obtain the quantification of these genes. In parallel, LC-HRMS2 analyses were performed on the A. minutum cultured strains and revealed for all of them a toxin profile consisting of only GTX1 and GTX4. Toxin production was in the fg/cell range. Concomitantly with a massive bloom of A. minutum and A. catenella that occurred in Spring 2014 along the Syracuse coasts (Sicily, Italy), four seawater samples were collected and analyzed by LC-HRMS and MS2. The analyzed extracts were found to contain a variety of PSP toxins, namely STX, NEO, the gonyautoxins GTX1-4, the N-sulfocarbamoyl derivatives C1/C2, B1 and B2 and the decarbamoyl ST
Posidonia oceanica meadows as sponge spicule traps
No full textA quantitative study on the sponge spicules present in a series of horizontal core samples, taken at different levels, from a
1.5 m thick living matte within the Posidonia oceanica meadow of Prelo Bay (Eastern Ligurian Sea), has been performed.
Sponge spicule amounts were evaluated by microscopical and chemical analyses. From the superficial samples the spicule
number decreased until 60–80 cm depth to increase progressively until the deepest studied layer, 140 cm depth. The
same results were obtained from the trend of spicule volume and biogenic silica tested by chemical analysis. Among the
recognisable spicule types, the most common are oxeas, followed by tylostyles, achantostyles and strongyles. However, oxeas,
tylostyles and achantostyles showed the same trend of the entire spicule population, whereas strongyles had an opposite trend
with a maximum value at the 80–100 cm depth. According to the hypothesis that the amount of spicules in the sediment
is proportional or at least related to the sponge biomass existing in the surrounding area, our data suggest that the sponge
assemblage of Prelo Bay should not have been constant in the past 100–200 years. Our hypothesis is that the rapid urban
and industrial development that occurred along the Ligurian coast after the Second World War, particularly in the 1960s,
had an important impact on the sponge assemblages of the area
The ChoCO-W prospective observational global study: Does COVID-19 increase gangrenous cholecystitis?
No full textBackground: The incidence of the highly morbid and potentially lethal gangrenous cholecystitis was reportedly increased during the COVID-19 pandemic. The aim of the ChoCO-W study was to compare the clinical findings and outcomes of acute cholecystitis in patients who had COVID-19 disease with those who did not. Methods: Data were prospectively collected over 6 months (October 1, 2020, to April 30, 2021) with 1-month follow-up. In October 2020, Delta variant of SARS CoV-2 was isolated for the first time. Demographic and clinical data were analyzed and reported according to the STROBE guidelines. Baseline characteristics and clinical outcomes of patients who had COVID-19 were compared with those who did not. Results: A total of 2893 patients, from 42 countries, 218 centers, involved, with a median age of 61.3 (SD: 17.39) years were prospectively enrolled in this study; 1481 (51%) patients were males. One hundred and eighty (6.9%) patients were COVID-19 positive, while 2412 (93.1%) were negative. Concomitant preexisting diseases including cardiovascular diseases (p < 0.0001), diabetes (p < 0.0001), and severe chronic obstructive airway disease (p = 0.005) were significantly more frequent in the COVID-19 group. Markers of sepsis severity including ARDS (p < 0.0001), PIPAS score (p < 0.0001), WSES sepsis score (p < 0.0001), qSOFA (p < 0.0001), and Tokyo classification of severity of acute cholecystitis (p < 0.0001) were significantly higher in the COVID-19 group. The COVID-19 group had significantly higher postoperative complications (32.2% compared with 11.7%, p < 0.0001), longer mean hospital stay (13.21 compared with 6.51 days, p < 0.0001), and mortality rate (13.4% compared with 1.7%, p < 0.0001). The incidence of gangrenous cholecystitis was doubled in the COVID-19 group (40.7% compared with 22.3%). The mean wall thickness of the gallbladder was significantly higher in the COVID-19 group [6.32 (SD: 2.44) mm compared with 5.4 (SD: 3.45) mm; p < 0.0001]. Conclusions: The incidence of gangrenous cholecystitis is higher in COVID patients compared with non-COVID patients admitted to the emergency department with acute cholecystitis. Gangrenous cholecystitis in COVID patients is associated with high-grade Clavien-Dindo postoperative complications, longer hospital stay and higher mortality rate. The open cholecystectomy rate is higher in COVID compared with non -COVID patients. It is recommended to delay the surgical treatment in COVID patients, when it is possible, to decrease morbidity and mortality rates. COVID-19 infection and gangrenous cholecystistis are not absolute contraindications to perform laparoscopic cholecystectomy, in a case by case evaluation, in expert hands. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s)
