title: Within-mat variability in anatoxin-a and homoanatoxin-a production among benthic Phormidium (cyanobacteria) strains.
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 cm(2) 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.
authors.affiliation: Cawthron Institute, Nelson 7042, New Zealand. susie.wood@cawthron.org.nz
authors.forename: Susanna A
authors.initials: SA
authors.lastname: Wood
authors.forename: Francine M J
authors.initials: FM
authors.lastname: Smith
authors.forename: Mark W
authors.initials: MW
authors.lastname: Heath
authors.forename: Thomas
authors.initials: T
authors.lastname: Palfroy
authors.forename: Sally
authors.initials: S
authors.lastname: Gaw
authors.forename: Roger G
authors.initials: RG
authors.lastname: Young
authors.forename: Ken G
authors.initials: KG
authors.lastname: Ryan
mesh_terms: D001427:Bacterial Toxins / Q000032:analysis*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000032:analysis*; D000458:Cyanobacteria / Q000737:chemistry* / Q000235:genetics*; D000087522:Cyanobacteria Toxins; D008401:Gas Chromatography-Mass Spectrometry; D005798:Genes, Bacterial; D009498:Neurotoxins / Q000032:analysis; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D045483:Rivers / Q000382:microbiology; D017423:Sequence Analysis, RNA; D014326:Tropanes / Q000032:analysis*
chemical_list: D001427:Bacterial Toxins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D000087522:Cyanobacteria Toxins; D009498:Neurotoxins; D012336:RNA, Ribosomal, 16S; D014326:Tropanes; C524097:homoanatoxin-a; C509783:anatoxin a