A study on the mechanism of domoic acid production by a pennate diatom.

关于多系假单胞菌软骨藻酸的产生机制，提出了一种假设，即软骨藻酸的产生可能是由于藻类细胞对细菌或某些细菌产物的异养吸收。为了阐明这一假说，进行了一些培养实验，主要是关于软骨藻酸的生产与其光合作用，铁吸收和细菌共存的比较。对多系假单胞菌的非纯培养物和纯培养物进行软骨藻酸和溶解铁浓度的测定。在非纯培养物中溶解铁耗尽后，软骨藻酸的大量产生就开始了。然而，在无菌培养的情况下，在溶解铁耗尽后10天仅观察到低水平的软骨藻酸产生。这一结果表明，软骨藻酸产生不仅与溶解铁耗尽有关，而且与细菌的共存有关。在无菌培养的情况下，少量细菌可能在藻类细胞内存活，并可能有助于产生软骨藻酸。细菌对多系假单胞菌生产软骨藻酸的影响受到正常透析膜（m.w.）12，000截值），但它不受0.2 μm膜过滤器的干扰，表明细菌对软骨藻酸生产的影响不需要细菌和藻类之间的直接接触。在黑暗条件下，非纯性P. multiseries培养物中软骨藻酸的产生停止，并且通过添加30 μM ATP、NADP、NADPH和葡萄糖不能恢复。这些结果表明，软骨藻酸的产生可能与溶解铁的消耗和细菌产物与铁的螯合有关，随后被光合作用下的藻细胞吸收。

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.