MEPS 131:225-233 (1996)  -  doi:10.3354/meps131225

Effects of silicate limitation on production of domoic acid, a neurotoxin, by the diatom Pseudo-nitzschia multiseries. I. Batch culture studies

Pan Y, Subba Rao DV, Mann KH, Brown RG, Pocklington R

Domoic acid (DA) production by Pseudo-nitzschia multiseries (Hasle) was studied at various silicate concentrations and under silicate perturbation. Both slowly dividing and non-dividing populations produced DA, and the production rates were inversely correlated with the ambient silicate concentrations. Production of DA was significantly enhanced when overall cell metabolism (i.e. growth rate) declined as a result of silicate stress. Following silicate starvation, cultures supplemented with silicate registered uptake, but suspended DA production. Results suggest that luxury uptake of Si by P. multiseries may happen only in physiologically active populations, i.e. the exponential phase, but not in the stationary phase. There were 2 stages of DA production. The first stage corresponded to a decline in growth caused by moderately low levels of remaining silicate in the medium, while the second stage was caused by severe silicate limitation. The production rate during the second stage (13.67 to 30.20 fg DA cell-1 d-1) was about an order of magnitude higher than during the first stage (0.97 to 4.98 fg DA cell-1 d-1). Increases and decreases in cellular DA content corresponded to decreases and increases in growth rates.

Domoic acid . Pseudo-nitzschia multiseries . Silicate limitation . Batch culture

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