| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2002: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Regarding the domoic acid production mechanism of P. multiseries, a hypothesis was made that domoic acid production might be occurred as a result of a heterotrophic uptake of bacteria or some bacterial products by algal cells. In order to clarify this hypothesis, a few culture experiments were primarily performed concerning the domoic acid production comparing with its photosynthesis, iron uptake and bacterial co-existence. Determination of the non-axenic and axenic culture of P. multiseries was done for both domoic acid and dissolved iron concentration. Significant amount of domoic acid production was started just after the depletion of dissolved iron in non-axenic culture. However, in case of axenic culture, just a low level of domoic acid production was observed 10 days after the depletion of dissolved iron, This results suggest that domoic acid production occurs not only in association with dissolved iron depletion but also with the co-existence of bacteria. In case of axenic culture, small number of bacteria might be alive inside the algal cells and might help producing domoic acid. The influence of bacteria on the production of domoic acid by P. multiseries was disturbed by a normal dialyzing membrane (m.w. 12,000 cut off), however it was not disturbed by a 0.2 μm membrane filter, suggesting that the bacterial effect on the domoic acid production does not need direct contact between bacteria and algae. Domoic acid production in non-axenic P. multiseries culture was stopped under dark conditions and was not recovered by adding 30 μM ATP, NADP, NADPH, and glucose. These results suggest that domoic acid production of P. multiseries might be occurred in association with depletion of dissolved iron and some bacterial products chelated with iron, followed by being up-taken by algae cell under photosynthesis.
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