title: The role of nitrogen and phosphorus in regulating Phormidium sp. (cyanobacteria) growth and anatoxin production.
abstract: Benthic proliferations of the cyanobacteria Phormidium can cover many kilometres of riverbed. Phormidium can produce neurotoxic anatoxins and ingestion of benthic mats has resulted in numerous animal poisonings in the last decade. Despite this, there is a poor understanding of the environmental factors regulating growth and anatoxin production. In this study, the effects of nitrogen and phosphorus on the growth of two Phormidium strains (anatoxin-producing and non-anatoxin-producing) were examined in batch monocultures. Cell concentrations were significantly reduced under reduced nitrogen (ca. <0.100 mM) and phosphorus conditions (ca. <0.003 mM). Cell concentrations and maximum growth rates were higher for the non-anatoxin-producing strain in all treatments, suggesting there may be an energetic cost to toxin production. Cellular anatoxin concentrations were lowest (169 fg cell(-1)) under the high-nitrogen and high-phosphorus treatment. This supports the growth-differentiation balance hypothesis that suggests actively dividing and expanding cells are less likely to produce secondary-metabolites. Anatoxin quota was highest (>407 fg cell(-1)) in the reduced phosphorus treatments, possibly suggesting that it is produced as a stress response to growth limiting conditions. In all treatments there was a 4-5-fold increase in anatoxin quota in the lag growth phase, possibly indicating it may provide a physiological benefit during initial substrate colonization.
authors: Environmental Science Department, Greater Wellington Regional Council, Shed 39, 2 Fryatt Quay, Pipitea, Wellington, 6111, New Zealand markheath85@gmail.com.
authors: Mark
authors: M
authors: Heath
authors: Coastal and Freshwater, Cawthron Institute, 98 Halifax St East, Nelson, 7042, New Zealand Department of Biological Sciences, University of Waikato, Private bag 3015, Hamilton, 3240, New Zealand.
authors: Susie A
authors: SA
authors: Wood
authors: Coastal and Freshwater, Cawthron Institute, 98 Halifax St East, Nelson, 7042, New Zealand.
authors: Roger G
authors: RG
authors: Young
authors: School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, 6140, New Zealand.
authors: Ken G
authors: KG
authors: Ryan
mesh_terms: D000458:Cyanobacteria / Q000254:growth & development* / Q000378:metabolism*; D000087522:Cyanobacteria Toxins; D009584:Nitrogen / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D014326:Tropanes / Q000378:metabolism*
chemical_list: D000087522:Cyanobacteria Toxins; D014326:Tropanes; D010758:Phosphorus; C509783:anatoxin a; D009584:Nitrogen
keywords: Phormidium; anatoxin; homoanatoxin; nitrogen; phosphorus