Domoic Acid Improves the Competitive Ability of Pseudo-nitzschia delicatissima against the Diatom Skeletonema marinoi (original) (raw)
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Marine Ecology Progress Series, 2004
The effect of elevated pH on growth and on production of the neurotoxin domoic acid was studied in selected diatoms belonging to the genera Pseudo-nitzschia and Nitzschia. Growth of most of the 11 species studied stopped at pH values of 8.7 to 9.1. However, for P. delicatissima and N. navis-varingica the pH limit for growth was higher, 9.3 and 9.7 to 9.8, respectively. A compilation of all available data on the pH limits for growth of marine planktonic diatoms suggests that species from ponds and rock pools all have higher limits than coastal and oceanic species. Taking only coastal and oceanic species into account, the data suggest that smaller species have a higher upper pH limit for growth than larger species. Elevated pH induced production of domoic acid in P. multiseries in amounts comparable to those detected previously under silicate and phosphate limitation. As Pseudo-nitzschia species are found in high concentrations in nutrient-enriched areas, high pH and hence induction of the production of domoic acid would be expected during blooms. These results may help to understand when and why Pseudo-nitzschia species produce domoic acid in the field.
Domoic acid: The synergy of iron, copper, and the toxicity of diatoms
Limnology and Oceanography, 2005
Diatom blooms generated by the alleviation of iron limitation in high nitrate-low chlorophyll (HNLC) regions of the oceans often are composed of pennate diatoms of the genus Pseudo-nitzschia, many of which periodically produce the potent neurotoxin domoic acid. We show that toxigenic diatoms have an inducible high-affinity iron uptake capability that enables them to grow efficiently on iron complexed by strong organic ligands in seawater. This low-iron adaptive strategy requires copper and domoic acid, a copper chelator whose production increases sharply when both iron and copper are limiting. Addition of either domoic acid or copper to seawater improves the growth of Pseudo-nitzschia spp. on strongly complexed iron during deck incubation experiments with natural phytoplankton. Our findings indicate that domoic acid is a functional component of the unusual high-affinity iron acquisition system of these organisms. This system may help explain why Pseudo-nitzschia spp. are persistent seed populations in oceanic HNLC regions, as well as in some neritic regions. Our findings also indicate that in the absence of an adequate copper supply, iron-limited natural populations of Pseudo-nitzschia will become increasingly toxic.
Journal of Phycology, 1996
Production of domozc acid (DA), a neurotoxzn, by the din to vi Pseudon i t z sc h i a mu 1 ti se r i es ( p rev zo usly Nitzschia pungensf: multiseries) Hasle and zts cellular chernzcal composztion were studied in phosphate-lzmited cheinohtat contznuous cultures and in subseque?1t batch cultures. Under steaclj-state chelnostat condztzons, D A production increased frow 0 . 0 1 to 0.26 pg DA.cell-"d-' as the growth rate decreased. W h e n the nutrzent supply was discoutinuecl (to produce a batch culture), D A production was eiahanced bq a factor of ca 3. D A productzon was teniporarzlj suspended upon addztioil of phosphate to the batch cultures but resumed 1 d later at a hzgher rate coincident ulith the decline of phosphate uptake. I n both steadystate contznuous culture and batch culture, more D A was produced when alkaline phosphatase actzuzty (APA) urns high The associatzon of high DA production with high leilels of APi4 and high cellular N:P ratios strong11 suggests that phosphate liinitatzon enhances D A productzon. Also, DL4 production was hzgh when other przmary metabolism (e.g. uptake of carbon, nitrogen, phosphorus and szlicon, and cell d i m i o n ) was low, but chlorophyll a and adenoszne trzphosphate were general11 hzgh. Thzs suggests that the Jyntheszs of DA requires a substantial amount of bzogenzc energ).
Lack of allelopathic effects of the domoic acid-producing marine diatom Pseudo-nitzschia multiseries
Marine Ecology Progress Series, 2005
Many Pseudo-nitzschia species produce the toxin domoic acid, which accumulates in the food web during blooms, sometimes causing amnesic shellfish poisoning (ASP) in higher trophic levels, including humans. In addition, Pseudo-nitzschia species have been reported to form longlasting monospecific blooms, and a possible explanation for this could be allelopathic effects of the toxin, since domoic acid has been detected in high amounts in the surrounding medium in stationary growth phase. We therefore examined the potential allelopathic effects of P. multiseries and its toxin domoic acid. In mixed-batch culture studies of domoic acid-producing P. multiseries and the algal test species Chrysochromulina ericina, Heterocapsa triquetra, Eutreptiella gymnastica and Rhodomonas marina, no allelopathic effects of P. multiseries were found. Different growth results using 2 different strains of P. multiseries grown with C. ericina were explained by minor differences in pH. Bioassays testing the effect of domoic acid itself on 9 different phytoplankton species, namely C. ericina, E. gymnastica, Karenia mikimotoi, H. triquetra, Heterosigma akashiwo, Prorocentrum minimum, P. micans, Pyramimonas propulsa and R. marina confirmed a lack of allelopathic effects of the toxin. This lack of allelopathic effect of the shellfish-poisoning toxin domoic acid seems to correspond with the results of phytoplankton species causing DSP (diarrheic shellfish poisoning) and PSP (paralytic shellfish poisoning), where it appears that these shellfish-poisoning toxins do not cause allelopathic effects either.
Marine Drugs, 2014
Bacteria are known to influence domoic acid (DA) production by Pseudo-nitzschia spp., but the link between DA production and physiology of diatoms requires more investigation. We compared a toxic P. multiseries to a non-toxic P. delicatissima, investigating links between DA production, physiological parameters, and co-occurring bacteria. Bacterial communities in cultures of both species were reduced by antibiotic treatment, and each of the diatoms was inoculated with the bacterial community of the other species. The physiology of P. delicatissima was minimally affected by the absence of bacteria or the presence of alien bacteria, and no DA was detected. P. multiseries grew faster without bacteria, did not produce a significant amount of DA, and exhibited physiological characteristics of healthy cells. When grown with alien bacteria, P. multiseries did not grow and produced more DA; the physiology of these cells was affected, with decreases in chlorophyll content and photosynthetic efficiency, an increase in esterase activity, and almost 50% mortality of the cells. The alien bacterial community had morphological and cellular characteristics very different from the original bacteria, and the number of free-living bacteria per algal cell was much higher, suggesting the involvement of bacteria in DA production.
Marine Chemistry, 2001
Toxigenic species of the pennate diatom Pseudo-nitzschia can produce domoic acid DA , an analog of the excitatory Ž . neurotransmitter glutamate and known to cause the human illness amnesic shellfish poisoning ASP . Although the trophic transfer of this phycotoxin resulting in mass marine bird and mammal mortality has recently been demonstrated, the physiological role of domoic acid to the causative organism is still unknown. Domoic acid is a small tricarboxylate amino acid whose structure resembles that of known iron-complexing agents produced by terrestrial plants, such as mugineic acid. This similarity in chemical structure of domoic acid to other phytosiderophores suggests a role for domoic acid as a trace metal chelator. Using a highly sensitive adsorptive cathodic stripping voltammetric technique, we investigated the iron and copper-binding characteristics of domoic acid revealing it does form chelates with both iron and copper and with the cond 8.7 " 0.5 y1 c o n d 9 . 0 " 0.2 y1 Ž cond
Biosynthesis of domoic acid by the diatom Pseudo-nitzschia multiseries
Natural toxins, 1998
The biosynthesis of the neurotoxin domoic acid (DA) in the diatom Pseudo-nitzschia multiseries was investigated using 13C- and 14C-labelled precursors. The labelling pattern determined by NMR spectroscopy following incorporation of [1,2-13C2]-acetate showed enrichment of every carbon of DA. The enrichment levels were consistent with a biosynthetic pathway involving two different intermediate precursor units. Addition of labelled acetate either early or late during exponential growth gave similar patterns and levels of incorporation. Analysis of the labelling pattern indicated that DA is biosynthesised by condensation of an isoprenoid intermediate with another intermediate derived from the tricarboxylic acid (TCA) cycle. The absence of deuterium at C2 in DA following incorporation of [2-13C, 2H3]-acetate is consistent with alpha-ketoglutarate or a derivative as the TCA cycle-derived intermediate. The different incorporation efficiencies of acetate into the putative precursor intermed...