Are Known Cyanotoxins Involved in the Toxicity of Picoplanktonic and Filamentous North Atlantic Marine Cyanobacteria?

Bárbara Frazão,Rosário Martins,Vitor Vasconcelos

doi:10.3390/md8061908

Abstract

Eight marine cyanobacteria strains of the genera Cyanobium, Leptolyngbya, Oscillatoria, Phormidium, and Synechococcus were isolated from rocky beaches along the Atlantic Portuguese central coast and tested for ecotoxicity. Strains were identified by morphological characteristics and by the amplification and sequentiation of the 16S rDNA. Bioactivity of dichloromethane, methanol and aqueous extracts was assessed by the Artemia salina bioassay. Peptide toxin production was screened by matrix assisted laser desorption/ionization time of flight mass spectrometry. Molecular analysis of the genes involved in the production of known cyanotoxins such as microcystins, nodularins and cylindrospermopsin was also performed. Strains were toxic to the brine shrimp A. salina nauplii with aqueous extracts being more toxic than the organic ones. Although mass spectrometry analysis did not reveal the production of microcystins or other known toxic peptides, a positive result for the presence of mcyE gene was found in one Leptolyngbya strain and one Oscillatoria strain. The extensive brine shrimp mortality points to the involvement of other unknown toxins, and the presence of a fragment of genes involved in the cyanotoxin production highlight the potential risk of cyanobacteria occurrence on the Atlantic coast.

Highlights

Cyanobacteria are known for their diversity in terms of morphological, physiological and toxicological properties
In this work we evaluated the potential toxicity of marine cyanobacteria isolated from the central coast of Portugal by means of biological, chemical and molecular biology analysis
We found that aqueous and organic extracts of marine cyanobacteria from the coccoid genera Cyanobium and Synechococcus and the filamentous genera Leptolyngbya, Oscillatoria and Phormidium isolated from the Portuguese coast induced acute toxicity in nauplii of the brine shrimp A. salina

Summary

Introduction

Cyanobacteria are known for their diversity in terms of morphological, physiological and toxicological properties. Together with the production of potent toxins, cyanobacteria produce many substances interesting in terms of antifungal, antibiotic and anticancerigenous activities [2,3]. The occurrence and ecotoxicology of cyanobacteria are well documented in freshwater habitats [4,5]. As described for cyanobacteria blooms in freshwater and brackish waters, the increase in cyanobacteria bloom formation registered in coastal areas has been attributed to factors such as high irradiation, high temperatures and increased nutrient loading, as a consequence of human population growth near these locations [8,9,10,11]. Similar to other littoral areas of the world, the Portuguese coast has been subjected to an increased human pressure and, coastal eutrophication

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