The sxt Gene and Paralytic Shellfish Poisoning Toxins as Markers for the Monitoring of Toxic Alexandrium Species Blooms

Paralytic shellfish poisoning (PSP) is a serious human illness caused by the ingestion of seafood contaminated with saxitoxin and its derivatives (STXs). These toxins are produced by some species of marine dinoflagellates within the genus Alexandrium. In the Mediterranean Sea, toxic Alexandrium spp. blooms, especially of A. minutum, are frequent and intense with negative impact to coastal ecosystem, aquaculture practices and other economic activities. We conducted a large scale study on the sxt gene and toxin distribution and content in toxic dinoflagellate A. minutum of the Mediterranean Sea using both quantitative PCR (qPCR) and HILIC-HRMS techniques. We developed a new qPCR assay for the estimation of the sxtA1 gene copy number in seawater samples during a bloom event in Syracuse Bay (Mediterranean Sea) with an analytical sensitivity of 2.0 × 10° sxtA1 gene copy number per reaction. The linear correlation between sxtA1 gene copy number and microalgal abundance and between the sxtA1 gene and STX content allowed us to rapidly determine the STX-producing cell concentrations of two Alexandrium species in environmental samples. In these samples, the amount of sxtA1 gene was in the range of 1.38 × 105 − 2.55 × 108 copies/L and the STX concentrations ranged from 41−201 nmol/L. This study described a potential PSP scenario in the Mediterranean Sea.Versión del editor5,228

Identification of Palytoxin–Ca 2+

More than 40 years after its isolation, the understanding of how palytoxin interacts with biological systems has yet to be fully determined. The Na(+),K(+)-ATPase pump constitutes a molecular receptor for palytoxin that is able to convert the pump into an open channel, with consequent loss of cellular K(+) and remarkable rise of cytosolic Na(+) levels. In addition, a slight permeability to Ca(2+) is detected when palytoxin binds to the pump. It has been demonstrated that the increase of cytosolic free Ca(2+) concentration gives rise to downstream events ultimately leading to cell death. The widely accepted recognition of the dependence of important cellular events on calcium ion concentration propelled us to investigate the occurrence of palytoxin-Ca(2+) complex in aqueous solution by NMR- and molecular modeling-based approach. We identified two specific regions of palytoxin where Ca(2+) is preferentially coordinated. This study constitutes the first characterization of a calcium complex with palytoxin and, as such, is expected to support the investigation of the toxin molecular bioactivity

Toxin-Producing Ostreopsis cf. ovata are Likely to Bloom Undetectedalong Coastal Areas

Mass appearances of the toxic dinoflagellate genus Ostreopsis are known to cause dangerous respiratory symptoms in humans exposed to aerosols. The outbreaks can appear in shallow marine waters of temperate regions around the globe. We followed a massive bloom event on a public beach on the northern Adriatic coast near Rovinj, Croatia. We identified the responsible species and the produced toxins as well as the dynamics of the event with respect to environmental conditions. Ostreopsis cf. ovata appeared in masses from September through October 2010 on a public beach near Rovinj, Croatia but stayed undetected by public health organizations. Respiratory symptoms were observed whenever humans were exposed to substrate samples containing large numbers of Ostreopsis cells. During the mass abundance of O. cf. ovata also exposure to the aerosols on the beach evoked respiratory symptoms in humans. Our measurements showed high cell abundances and high toxin contents with a stable relative contribution of putative Palytoxin and Ovatoxins a-e. Artificial beach structures proved to dramatically reduce settling of the observed Ostreopsis biofilm. Blooms like those reported herein have a high potential to happen undetected with a high potential of affecting the health of coastal human populations. Increased monitoring efforts are therefore required to understand the ecology and toxicology of those bloom events and reduce their negative impact on coastal populations