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Within-Mat Variability in Anatoxin-a and Homoanatoxin-a Production among Benthic Phormidium (Cyanobacteria) Strains
Cawthron Institute, Private Bag 2, Nelson 7042, New Zealand
Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
* Author to whom correspondence should be addressed.
Received: 21 September 2012; in revised form: 14 October 2012 / Accepted: 16 October 2012 / Published: 19 October 2012
(This article belongs to the Special Issue Cyanotoxins
Abstract: Benthic Phormidium mats can contain high concentrations of the neurotoxins anatoxin-a and homoanatoxin-a. However, little is known about the co-occurrence of anatoxin-producing and non-anatoxin-producing strains within mats. There is also no data on variation in anatoxin content among toxic genotypes isolated from the same mat. In this study, 30 Phormidium strains were isolated from 1 cm2 sections of Phormidium-dominated mats collected from three different sites. Strains were grown to stationary phase and their anatoxin-a, homoanatoxin-a, dihydroanatoxin-a and dihydrohomoanatoxin-a concentrations determined using liquid chromatography-mass spectrometry. Each strain was characterized using morphological and molecular (16S rRNA gene sequences) techniques. Eighteen strains produced anatoxin-a, dihydroanatoxin-a or homoanatoxin-a. Strains isolated from each mat either all produced toxins, or were a mixture of anatoxin and non-anatoxin-producing genotypes. Based on morphology these genotypes could not be separated. The 16S rRNA gene sequence comparisons showed a difference of at least 17 nucleotides among anatoxin and non-anatoxin-producing strains and these formed two separate sub-clades during phylogenetic analysis. The total anatoxin concentration among toxic strains varied from 2.21 to 211.88 mg kg−1 (freeze dried weight), representing a 100 fold variation in toxin content. These data indicate that both the relative abundance of anatoxin and non-anatoxin-producing genotypes, and variations in anatoxin producing capability, can influence the overall toxin concentration of benthic Phormidium mat samples.
Keywords: 16S rRNA gene sequence; anaF gene; anatoxin-a; benthic mats; cyanobacteria; homoanatoxin-a; Phormidium
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Wood, S.A.; Smith, F.M.J.; Heath, M.W.; Palfroy, T.; Gaw, S.; Young, R.G.; Ryan, K.G. Within-Mat Variability in Anatoxin-a and Homoanatoxin-a Production among Benthic Phormidium (Cyanobacteria) Strains. Toxins 2012, 4, 900-912.
Wood SA, Smith FMJ, Heath MW, Palfroy T, Gaw S, Young RG, Ryan KG. Within-Mat Variability in Anatoxin-a and Homoanatoxin-a Production among Benthic Phormidium (Cyanobacteria) Strains. Toxins. 2012; 4(10):900-912.
Wood, Susanna A.; Smith, Francine M. J.; Heath, Mark W.; Palfroy, Thomas; Gaw, Sally; Young, Roger G.; Ryan, Ken G. 2012. "Within-Mat Variability in Anatoxin-a and Homoanatoxin-a Production among Benthic Phormidium (Cyanobacteria) Strains." Toxins 4, no. 10: 900-912.