Heath Mark, Wood Susie A, Young Roger G, Ryan Ken G
Environmental Science Department, Greater Wellington Regional Council, Shed 39, 2 Fryatt Quay, Pipitea, Wellington, 6111, New Zealand
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.
FEMS Microbiol Ecol. 2016 Mar;92(3). doi: 10.1093/femsec/fiw021. Epub 2016 Feb 8.
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.
蓝藻席藻的底栖增殖可覆盖数公里的河床。席藻可产生神经毒性的类毒素，在过去十年中，底栖藻垫的摄入已导致大量动物中毒。尽管如此，人们对调节其生长和类毒素产生的环境因素了解甚少。在本研究中，在分批单培养中研究了氮和磷对两种席藻菌株（产类毒素和不产类毒素）生长的影响。在低氮（约<0.100 mM）和低磷条件（约<0.003 mM）下，细胞浓度显著降低。在所有处理中，不产类毒素的菌株的细胞浓度和最大生长速率更高，这表明毒素产生可能存在能量成本。在高氮和高磷处理下，细胞类毒素浓度最低（169 fg细胞-1）。这支持了生长-分化平衡假说，即活跃分裂和扩展的细胞不太可能产生次生代谢产物。在低磷处理中，类毒素配额最高（>407 fg细胞-1），这可能表明它是作为对生长限制条件的应激反应而产生的。在所有处理中，滞后期生长阶段的类毒素配额增加了4-5倍，这可能表明它在初始底物定殖期间可能提供生理益处。
