Changes in toxins, intracellular and dissolved free amino acids of the toxic dinoflagellate Gymnodinium catenatum in response to changes in inorganic nutrients and salinity |
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Authors: | Flynn Kevin J; Fynn Krystyna; John Eurgain H; Reguera Beatriz; Reyero I; Franco Jose M |
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Institution: | 1Swansea Algal Research Unit, School of Biological Sciences, Universiry of Wales Swamea Singleton Park, Swamea SA2 8PP, UK
2Instituto Español de Oceanografia Apdo 1552, 36280, Vigo, Spain
3Instituto de Investigaciones Marinas (CSIC) Eduardo Cabello, 6, Vigo 36208, Spain |
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Abstract: | The paralytic shellfish poison prducing dinoflagellate Gymnodiniuncatemrum was subjected to changes in salinity, phosphate, ammoniumand nitrate using continuous culture and batch culture methods.In contrast with other algae, this species showed very slowchanges in the concentration of intracellular amino acids, inthe Gln:Glu ratio, and, in contrast with Alrsandnum spp., onlyslow changes in toxin content, during such events as N-feedingof Ndeprived cells or during nutrient deprivation. This organismwas found to be very susceptible to disturbance; maximum growthrates around 0.250.3 day1 with a minimum C:N massratio of 5.5, were attained when cultures were only disturbedby sampling once a day. P-deprived cells were larger (twicethe usual C content of 4 ng C cell1 and volume of 20pl). The content of free amino acids was always low (5% of cell-N),with low contributions made by arginine (the precursor for paralyticshellfish toxins). Cells growing using ammonium had the lowestC:N ratios and the highest proportion of intracellular aminoacids as arginine. The toxin profile (equal mole ratios of dcSTX,GTX5, dcGT2/3 C1 and C2, and half those values for C3 and C4)was stable and the toxin concentration varied between 0.2 and1 mM STX equivalents (highest when ammonium was not limiting,lowest in P-deprived cells, though as the latter were largertoxin per cell was not so variable). Decreased salinity didnot result in increases in toxin content. Significant amountsof amino acids (mainly serine and glycine, with a total oftenexceeding 4 µM) accumulated in the growth medium duringbatch growth even though the cultures were not bacteria free.
4Present address: Instituto Español de Oceanografia,Apdo 1552, 36280, Vigo, Spain |
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