TEM identification of Pseudo-nitzschia species from Lisbon Bay (NE Atlantic) (original) (raw)
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Harmful Algae
The marine diatom genus Pseudo-nitzschia, the major known producer of the neurotoxin domoic acid (DA) responsible for the amnesic shellfish poisoning (ASP) syndrome in humans and marine mammals, is globally distributed. The genus presents high species richness in the Argentine Sea and DA has been frequently detected in the last few years in plankton and shellfish samples, but the species identity of the producers remains unclear. In the present work, the distribution and abundance of Pseudo-nitzschia species and DA were determined from samples collected on two oceanographic cruises carried out through the Argentine Sea ($39-47 S) during summer and spring 2013. Phytoplankton composition was analysed by light and electron microscopy while DA was determined by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The genus Pseudo-nitzschia was recorded in 71 and 86% of samples collected in summer and spring, respectively, whereas DA was detected in only 42 and 21% of samples, respectively. Microscopic analyses revealed at least five potentially toxic species (P. australis, P. brasiliana, P. fraudulenta, P. pungens, P. turgidula), plus putatively non-toxigenic P. dolorosa, P. lineola, P. turgiduloides and unidentified specimens of the P. pseudodelicatissima complex. The species P. australis showed the highest correlation with DA occurrence (r = 0.55; p < 0.05), suggesting its importance as a major DA producer in the Argentine Sea. In the northern area and during summer, DA was associated with the presence of P. brasiliana, a species recorded for the first time in the Argentine Sea. By contrast, high concentrations of P. fraudulenta, P. pungens and P. turgidula did not correspond with DA occurrence. This study represents the first successful attempt to link toxigenicity with Pseudo-nitzschia diversity and cell abundance in field plankton populations in the southwestern Atlantic.
Domoic acid-a neurotoxic amino acid produced by the marine diatom Nitzschia pungens in culture
Canadian journal of …, 1988
1988. Domoic acida neurotoxic amino acid produced by the marine diatom Nitzschia pungens in culture. Can. 8. Fish Aquat. Sci. 45: 2076-2079 D~aring late 1987, an outbreak of poisoning resulting from the ingestion sf cultivated blue mussels (Mytilus edeblis) from a localized area in eastern Canada (Cardigan Bay, Prince Edward Island) was associated with massive blooms of Nitzschia pungens, a widely distributed diatom not previously known to produce toxins; human fatalities resulted. Here we provide proof that the causative agent, dornoic acid, is indeed produced by this diatom. Although no dornoic acid could be detected (<2 ngsrnL-l) in culture medium (FE) prepared from Cardigan River water, it was found in cultures of Nitzschia pungens grown in this medium at concentrations ranging from 0.03 to 0.8 pg-cell-1 in various separate cultures harvested for chemical analysis 7-68 d after inoculation.
African Journal of Marine Science, 2014
A unialgal culture of a Pseudo-nitzschia species dominant in the plankton of Algoa Bay in the spring of 2012 was established by isolation of clonal chains of cells. Identification of the species as Pseudo-nitzschia multiseries was based on frustule morphometrics provided by light and scanning electron microscopy, and confirmed by phylogenetic analysis of the LSU rDNA gene. Cultures were shown to produce domoic acid (DA) as measured by ELISA and LC/MS-MS methods, and levels of cellular DA were ~0.1 pg cell -1 . Although it is recognised as a cosmopolitan species, these observations provide the first account of this toxic diatom in the coastal waters of South Africa.
Phycologia, 2012
ABSTRACT Pseudo-nitzschia is a globally distributed diatom genus, some species of which produce domoic acid (DA), the neurotoxin that causes amnesic shellfish poisoning. This toxin killed at least three humans in 1987, launching numerous studies concerning the identification, distribution, ecology and physiology of Pseudo-nitzschia spp. Since previous reviews in 1998, knowledge has been gained about the fate of DA, including its accumulation by marine animals and its degradation by light and bacteria. Molecular techniques and more precise microscopy have enabled the description of new Pseudo-nitzschia species, 15 since 2002, including ones that are cryptic and pseudo-cryptic. An increasing number of the 37 identified species, including oceanic and coastal species, have been studied in laboratory culture. The sexual reproduction of 14 species has been documented. Fourteen species have now been shown to be toxigenic, although some strains are not always toxic under the testing conditions. The biotic and abiotic factors that modify DA production are reviewed, with a focus on how new discoveries have changed our original hypotheses about control mechanisms. Recent studies confirm that silicate and phosphate limitation trigger DA production. However, stress by low concentrations of iron or high concentrations of copper are newly discovered triggers, suggesting a trace-metal chelation role for DA. Organic sources of nitrogen (urea and glutamine), as well as changes in pH, CO 2 , salinity and bacterial concentration, also enhance DA production. Laboratory and field studies sometimes give divergent results for conditions that are conducive to toxin production. Gaps in knowledge include further information about the whole genome of Pseudo-nitzschia (including sexual stages), mechanisms of DA production and decline, presence or absence of a resting stage, heterotrophic ability, impact of viruses and fungi, and a more complete description of the ecological and physiological roles of DA.
Diatom Research, 2011
Identification of species within the diatom genus Pseudo-nitzschia H. Peragallo, some of which produce the neurotoxin domoic acid (DA), causative agent of amnesic shellfish poisoning (ASP), is crucial for biotoxin monitoring and decision making concerning shellfish harvesting. The occurrence of this genus is reported here at species-complex resolution, for samples collected during one year from March 2006 to February 2007 in Bizerte Lagoon (northern Tunisia) and at one coastal station located in the southwest Mediterranean Sea. Six morphospecies (P. brasiliana Lundholm, Hasle & Fryxell, P. calliantha Lundholm, Moestrup & Hasle, P. delicatissima (Cleve) Heiden complex species, P. pseudodelicatissima (Hasle) Hasle, P. multistriata (Takano) Takano and P. seriata (Cleve) H. Peragallo group species)
Scientific Reports
The aim of this study was to develop and validate a high resolution melting (HRM) method for the rapid, accurate identification of the various harmful diatom Pseudo-nitzschia species in marine environments. Pseudo-nitzschia has a worldwide distribution and some species are toxic, producing the potent domoic acid toxin, which poses a threat to both human and animal health. Hence, it is important to identify toxic Pseudo-nitzschia species. A pair of primers targeting the LSU rDNA of the genus Pseudo-nitzschia was designed for the development of the assay and its specificity was validated using 22 control DNAs of the P. calliantha, P. delicatissima/P. arenysensis complex and P. pungens. The post-PCR HRM assay was applied to numerous unidentified Pseudo-nitzschia strains isolated from the northwestern Adriatic Sea (Mediterranean Sea), and it was able to detect and discriminate three distinct Pseudo-nitzschia taxa from unidentified samples. Moreover, the species-specific identification of Pseudo-nitzschia isolates by the HRM assay was consistent with phylogenetic analyses. The HRM assay was specific, robust and rapid when applied to high numbers of cultured samples in order to taxonomically identify Pseudonitzschia isolates recovered from environmental samples. Diatoms (class Bacillariophyceae) are among the most productive eukaryotic microalgae. They are found in oceans around the world and play a fundamental role in global biogeochemical cycles 1. Within the Bacillariophyceae class, the genus Pseudo-nitzschia is found in polar, temperate, subtropical and tropical regions 2 , although some Pseudo-nitzschia species are limited to distinct regional areas. Among the more than 37 species identified worlwide 3 , at least 12 Pseudo-nitzschia species are toxic. These species produce domoic acid (DA), a neurotoxin causing amnesic shellfish poisoning (ASP), which is responsible for many toxic blooms worldwide 2. Blooms of Pseudo-nitzschia spp. can be stimulated by nutrient (mainly nitrate and phosphate) input from various sources, such as upwelling, turbulence or riverine inputs, deriving largely from anthropogenic nutrient loads of agricultural and sewage origins 4. However, Pseudo-nitzschia blooms or occurrences are often a seasonal phenomenon in many coastal sites, and the frequency of toxic blooms generated by several species of Pseudo-nitzschia is increasing in various coastal areas worldwide 2. The impact of DA is evident in the marine food web. In fact, DA has been detected in the tissues of many invertebrates, fish, birds and marine mammals 5-7. In Canada in 1987 consumption of contaminated seafood 8 caused a serious outbreak of ASP resulting in human mortality. However, since this dramatic episode, there have been no reports of human deaths caused by ASP thanks to the institution of effective monitoring programs. Nevertheless, DA occurrence can have negative economic impact on shellfish aquaculture farms, since the molluscan shellfish remain the only known vector of DA to humans. The regions that are most affected by DA are Northern Europe, Canada and Northern United States. Low levels of DA have been detected in the Mediterranean Sea, but its presence has not been associated with harmful
Marine Ecology …, 2001
Domoic acid (DA), a potent neurotoxin, is synthesized by certain members of the ubiquitous marine diatom genus Pseudo-nitzschia. We recently detected elevated concentrations of DA in phytoplankton field samples from the northern Gulf of Mexico. In searching for a possible source of the toxin, we used a receptor-binding assay to detect DA activity in cultures of P. sp. cf. pseudodelicatissima (Hasle) isolated from this region and confirmed its presence in 2 of 7 clones using liquid chromatography coupled with tandem mass-spectrometric detection (LC-MS/MS). Unlike other toxic Pseudo-nitzschia species examined previously (e.g., P. multiseries, P. australis), cellular levels and net production of DA in these clones were highest in the early exponential phase, while the population growth rate was high and cell concentration was low. There was a negative correlation between cellular DA and cell concentration. The maximum cellular DA activity in cultures was 36 fg DA equiv. cell -1 . No net toxin production was evident in the stationary phase, yet extracellular DA levels increased markedly during this period to as much as 88% of the total DA in the cultures. Interestingly, these 2 toxic clones were able to enlarge their cell size after the apical axes declined to 15 to 25 µm, and these larger cells had considerably higher levels of DA than the original small cells. This study unequivocally establishes P. sp. cf. pseudodelicatissima as a source of DA in the northern Gulf of Mexico. Moreover, our work suggests that rapidly growing, rather than nutrient-limited, populations of this diatom should yield maximum net DA production rates and DA cell quotas. Thus, the presence of P. sp. cf. pseudodelicatissima cells, even at the low levels of early, rapidly growing bloom stages, can potentially lead to toxic events.