Studies on Bacteria Which Produce Paralytic Shellfish Toxins.

在大船渡湾，由于缺乏有毒鞭毛藻，贝类的毒性经常增加。这一现象提示存在未知的致病生物。最近，我们发现从塔玛兰Alexandrium tamarense分离的莫拉氏菌（Moraxella sp.）产生麻痹性贝类毒素（PSP毒素）。因此，这种细菌与贝类毒性的联系进行了研究。在没有有毒鞭毛藻的情况下，对贝类毒性增加时期海水中不同大小颗粒中PSP毒素的分析表明，细菌大小的颗粒中PSP毒素含量显著，其分布与贝类和鞭毛藻相似。海水中亦检出莫拉菌。这些发现表明海洋中产生PSP毒素的细菌的存在可能与贝类毒性有关。这也表明，在营养不良的条件下，细菌的毒素产量增加。因此，莫拉菌是在营养不良的条件下培养的。在自然海水中培养10天后，其毒素产量增加，这表明它在饥饿的条件下也会产生毒素。筛选了多种有毒鞭毛藻中产生PSP毒素的细菌。几乎所有鞭毛藻都产生胞内细菌，并表现出产毒能力。这些事实支持细胞内细菌是甲藻产生毒素所必需的观点。在有毒鞭毛藻中发现的细菌种类对鞭毛藻的菌株和种类都有特异性，表明这些细菌分布广泛。在没有鞭毛藻繁殖的地区收集的双壳类中检测到似乎来自细菌的PSP毒素。

In Ofunato Bay, the shellfish toxicity has been often observed to increase under absence of toxic dinoflagellates. This phenomenon suggests the presence of unknown causative organism (S). Recently, we have found that a bacterium Moraxella sp. isolated from Alexandrium tamarense produces paralytic shellfish toxins (PSP toxins). Thus the link of this bacterium with shellfish toxicity was examined. Analysis of PSP toxins in the particle fractions with different sizes collected from the seawater during the period when the shellfish toxicity increased under absence of toxic dinoflagellate showed that particles with bacterial size possess significant amount of PSP toxins, the profile of which was similar to that of shellfish and dinoflagellate. Moraxella sp. was also detected in the seawater. These findings show the presence of PSP toxins producing bacteria in the ocean that are possibly linked with shellfish toxicity. These also suggest that toxin productivity of the bacteria increases under nutrient poor conditions. Thus Moraxella sp. Was cultured under nutrient poor conditions. Its toxin productivity increased when it was cultured in the natural seawater and left for 10 days, indicating that it produces toxins under starved conditions. PSP toxins producing bacteria were screened in various species of toxic dinoflagellates. Almost all the dinoflagellates gave the intracellular bacteria which showed toxin productivity. These facts support the idea that intracellular bacteria are necessary for the toxin production of dinoflagellates. Bacterial species found in the toxic dinoflagellates were specific to strains as well as species of dinoflagellate, showing the wide distribution of these bacteria. PSP toxins which seemed to originate from bacteria were detected in the bivalves collected from the areas where no dinoflagellates bloom.