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

A review on the effects of environmental conditions on growth and toxin production of Ostreopsis ovata

Abstract Since the end of the\u201990s the occurrence of blooms of the benthic dinoflagellates Ostreopsis spp. is spreading in many tropical and temperate regions worldwide, sometimes causing benthonic biocenosis suffering and occasional human distress. O. ovata has been found to produce palytoxinlike compounds, a class of highly potent toxins. Since these cells are easily resuspended in the water column, the important role of hydrodynamism in the blooms development and decline has been highlighted; moreover, higher abundances of Ostreopsis spp. are usually recorded during warmer periods, characterized by high temperature and salinity and low hydrodinamism. The environmental conditions appear, therefore, to be one of the main factors determining the proliferation on these species, as testified by several field surveys. Laboratory studies on the effect of environmental parameters on growth and toxicity of O. ovata are rather scarce. With regards to the effect of temperature, it appears that different strains blooming along Italian coasts displayed different optima, in accordance to blooming periods, and that higher toxin levels correlated with best growth conditions. The increase in salinity was positively correlated with growth of an Adriatic strain while toxicity was lowest at the highest salinity value (40). Both nitrogen and phosphorus limitation determined a decrease in cell toxicity in contrast to what observed for several different toxic dinoflagellates

LC-High Resolution MSn and LC-Tandem mass spectrometry for a data merging of a Greek cyanobacteria biomass from Lake Kastoria

Microcystins (MCs) are a large group of structurally related compounds produced by cyanobacteria belonging to different genera, including the planktonic Microcystis, Planktothrix, Anabaena species, and the benthic Oscillatoria. There are more than 240 cyclic peptides and they have often been implicated in accidental human and animal poisonings along lake and estuarine shores. Nodularins are other cyanobacterial toxins produced by the species Nodularia spumigena sharing structural features with MCs, which occurs in brackish waters, essentially in the Baltic Sea, Australia, and New Zealand. All these compounds are potent inhibitors of serine/threonine protein phosphatases 1 and 2A, with hepatocytes being their final molecular target. A number of cyanopeptolins and micropeptines are known from literature to be produced by cyanobacteria, some of them toxic too. In the present study we analyzed a biomass sample collected in September 2014 from Lake of Kastoria (Greece) during a cyanobacterial bloom by using two different approaches: a targeted analysis by LC-tandem mass spectrometry at unit resolution and an untargeted approach by LC-High resolution LTQ Orbitrap MSn. A good correlation between the two approaches emerged but from untargeted analyses the presence of some MC variants that were not detected by LC-MS/MS emerged together with the presence of potentially new cyanopetolins