Multiple New Strains of Amphidomataceae (Dinophyceae) from the North Atlantic Revealed a High Toxin Profile Variability of Azadinium spinosum and a New Non-Toxigenic Az. cf. spinosum

Abstract

Azaspiracids (AZA) are a group of lipophilic toxins, which are produced by a few species of the marine nanoplanktonic dinoflagellates Azadinium and Amphidoma (Amphidomataceae). A survey was conducted in 2018 to increase knowledge on the diversity and distribution of amphidomatacean species and their toxins in Irish and North Sea waters (North Atlantic). We here present a detailed morphological, phylogenetic, and toxinological characterization of 82 new strains representing the potential AZA producers Azadinium spinosum and Amphidoma languida. A total of ten new strains of Am. languida were obtained from the North Sea, and all conformed in terms of morphology and toxin profile (AZA-38 and-39) with previous records from the area. Within 72 strains assigned to Az. spinosum there were strains of two distinct ribotypes (A and B) which consistently differed in their toxin profile (dominated by AZA-1 and -2 in ribotype A, and by AZA-11 and -51 in ribotype B strains). Five strains conformed in morphology with Az. spinosum, but no AZA could be detected in these strains. Moreover, they revealed significant nucleotide differences compared to known Az. spinosum sequences and clustered apart from all other Az. spinosum strains within the phylogenetic tree, and therefore were provisionally designated as Az. cf. spinosum. These Az. cf. spinosum strains without detectable AZA were shown not to cause amplification in the species-specific qPCR assay developed to detect and quantify Az. spinosum. As shown here for the first time, AZA profiles differed between strains of Az. spinosum ribotype A in the presence/absence of AZA-1, AZA-2, and/or AZA-33, with the majority of strains having all three AZA congeners, and others having only AZA-1, AZA-1 and AZA-2, or AZA-1 and AZA-33. In contrast, no AZA profile variability was observed in ribotype B strains. Multiple AZA analyses of a period of up to 18 months showed that toxin profiles (including absence of AZA for Az. cf. spinosum strains) were consistent and stable over time. Total AZA cell quotas were highly variable both among and within strains, with quotas ranging from 0.1 to 63 fg AZA cell−1. Cell quota variability of single AZA compounds for Az. spinosum strains could be as high as 330-fold, but the underlying causes for the extraordinary large variability of AZA cell quota is poorly understood.

Antibacterial Activity and Amphidinol Profiling of the Marine Dinoflagellate Amphidinium carterae (Subclade III)

“…There are far less sequences of Amphidinium available in GenBank compared to HAB species, but the isolates of A. carterae that cluster together with strain LACW11 within subclade-III appear to be globally distributed. In the context of potential inter-strain variability in the bioactivity of extracts of distinct isolates of this species, and of their chemical make-up, akin to the existing variability of toxin profiles among some HAB species [45,46], questions do arise with regard to their composition in amphidinols, which could potentially be used as chemical markers for the four previously identified subclades.…”

Current Research Status of Azaspiracids

“…Recently, these toxins have undergone structural modifications [42]. The toxins produced by different ribosomal subtypes of Azadinium spinosum exhibit variations, with subtype A mainly producing AZA-1 and AZA-2, while subtype B primarily produces AZA-11 and AZA-51 [43]. In the case of ribosomal subtype A of Azadinium pomorum, there is either no production or only a minimal amount of AZAs, whereas ribosomal subtype C can generate AZA-40 and AZA-2 [44].…”

Development of harmful algal blooms species responsible for lipophilic and amnesic shellfish poisoning intoxications in southwestern Mediterranean coastal waters

“…The azaspiracids toxins are the latest LSTs which were found first in Irish mussels in 1995 (James et al, 2002). Azadinium and Amphidoma genera have been known to be responsible for the production of these toxins (Tillmann et al, 2017(Tillmann et al, , 2021Ozawa et al, 2021). Bacchiocchi et al (2015) demonstrated the presence of AZAs in M. galloprovincialis in the Mediterranean Sea.…”