Morphology, phylogeny, growth rate and nodularin production of Nodularia spumigena from Brazil

ABSTRACT

Blooms of the toxic cyanobacterium Nodularia spumigena occur in various locations worldwide, but have not been observed in Brazil until recently. Three Nodularia strains were isolated from summer blooms in experimental shrimp production ponds of Penaeus vannamei in Rio Grande, in southern Brazil; these strains were characterized by morphology, phylogeny, growth rate and toxicity. The strains were identified as N. spumigena based on the size of vegetative cells, heterocytes and akinetes under a light microscope and based on the number of gas vesicles per μm² under a transmission electron microscope. The 16S rRNA gene sequences of the three strains showed high identity (> 99%) with N. spumigena sequences available on the NCBI database but were grouped closer in the phylogenetic tree with N. spumigena strains from Australia and USA than those from the Baltic Sea. The growth rate in batch culture varied between 0.2 and 0.6 μ d⁻¹ based on cell density, optical density and chlorophyll-a content. The three strains produced the hepatotoxin nodularin (ELISA plate kit) with similar toxicity values (4.8–4.9 µg l⁻¹). We conclude that the three isolated strains are N. spumigena with similar rates of growth and nodularin production. The presence of N. spumigena now represents a potential problem in aquaculture and estuarine environments in Brazil.

RESPONSIBLE EDITOR:

• Hongyue Dang

KEYWORDS:

• Cyanobacteria
• polyphasic approach
• 16S rRNA
• 16S/23S rRNA ITS
• ultrastructure
• toxin

Acknowledgements

We would like to thank Christiane Q. Lopes and Raquel W. Cunha for assistance with sample preparation and analysis at the Microscopy and Microanalysis Center of the Federal University of Rio Grande do Sul (UFRGS).

Disclosure Statement

No potential conflict of interest was reported by the authors.

ORCID

Clarisse Odebrecht http://orcid.org/0000-0001-7159-4713

Additional information

Funding

Financial support was provided through the Brazilian Long-term Ecological Research project of the Ministry of Sciences/National Research Council (CNPQ-PELD, Proc. 403805/2012-0) to Clarisse Odebrecht and a Ministry of Education (CAPES) grant to Savênia Bonoto da Silveira.