Domoic acid production in Nitzschia sp (Bacillariophyceae) isolated from ashrimp-culture pond in Do Son, Vietnam

Domoic acid (DA), a neuroexcitatory amino acid, was detected in batch cultu re of the newly recognized species Nitzschia navis-varingica Lundholm et Mo estrup, The production of DA by this diatom was confirmed by electrospray i onization mass spectrometry, The diatom was collected from a shrimp-culture pond in Do Son, Vietnam, The production of DA (1.7 pg cell(-1)) is within the levels reported for Pseudo-nitzchia multiseries (Hasle) Hasle, The DA p roduction started during the late exponential growth phase and reached a ma ximum during the early stationary growth phase. Maximum DA levels in the ax enic culture decreased to about half that of the nonaxenic culture (0.9 pg cell(-1) vs. 1.7 pg cell(-1)), suggesting that DA production by the new spe cies is influenced by bacteria.