title: Effects of nitrogen and phosphorus on anatoxin-a, homoanatoxin-a, dihydroanatoxin-a and dihydrohomoanatoxin-a production by Phormidium autumnale.
abstract: Anatoxins are powerful neuromuscular blocking agents produced by some cyanobacteria. Consumption of anatoxin-producing cyanobacterial mats or the water containing them has been linked to numerous animal poisonings and fatalities worldwide. Despite this health risk, there is a poor understanding of the environmental factors regulating anatoxin production. Non-axenic Phormidium autumnale strain CAWBG557 produces anatoxin-a (ATX), homoanatoxin-a (HTX) and their dihydrogen-derivatives dihydroanatoxin-a (dhATX) and dihydrohomoanatoxin-a (dhHTX). The effects of varying nitrogen and phosphorus concentrations on the production of these four variants were examined in batch monocultures. The anatoxin quota (anatoxin per cell) of all four variants increased up to four fold in the initial growth phase (days 0-9) coinciding with the spread of filaments across the culture vessel during substrate attachment. Dihydroanatoxin-a and dhHTX, accounted for over 60% of the total anatoxin quota in each nitrogen and phosphorus treatment. This suggests they are being internally synthesised and not just derived following cell lysis and environmental degradation. The four anatoxin variants differed in their response to varying nitrogen and phosphorus concentrations. Notably, dhATX quota significantly decreased (P ≤ 0.03) when nitrogen and phosphorus concentrations were elevated (nitrogen = 21 mg L(-1); phosphorus = 3 mg L(-1)), while HTX quota increased when the phosphorus concentrations were reduced (ca. < 0.08 mg L(-1)). This is of concern as HTX has a high toxicity and anatoxin producing P. autumnale blooms in New Zealand usually occur in rivers with low water column dissolved reactive phosphorus.
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand. Electronic address: markheath85@gmail.com.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Heath
authors.affiliation: Cawthron Institute, Private Bag 2, Nelson 7001, New Zealand; Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand.
authors.forename: Susanna A
authors.initials: SA
authors.lastname: Wood
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
authors.forename: Rafael F
authors.initials: RF
authors.lastname: Barbieri
authors.affiliation: Cawthron Institute, Private Bag 2, Nelson 7001, New Zealand.
authors.forename: Roger G
authors.initials: RG
authors.lastname: Young
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
authors.forename: Ken G
authors.initials: KG
authors.lastname: Ryan
mesh_terms: D001427:Bacterial Toxins / Q000096:biosynthesis*; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003470:Culture Media / Q000737:chemistry*; D000458:Cyanobacteria / Q000737:chemistry* / Q000187:drug effects; D008387:Marine Toxins / Q000096:biosynthesis*; D015233:Models, Statistical; D009584:Nitrogen / Q000032:analysis / Q000494:pharmacology*; D010758:Phosphorus / Q000032:analysis / Q000494:pharmacology*
chemical_list: D001427:Bacterial Toxins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003470:Culture Media; D008387:Marine Toxins; C524097:homoanatoxin-a; D010758:Phosphorus; D009584:Nitrogen
keywords: Anatoxin-a; Dihydroanatoxin-a; Dihydrohomoanatoxin-a; Homoanatoxin-a; Phormidium autumnale