Studies on Bacteria Which Produce Paralytic Shellfish Toxins.

在大船渡湾，经常观察到贝类毒性增加的情况下，有毒甲藻。这种现象表明存在未知的致病微生物（S）。最近，我们发现从塔玛亚历山大藻中分离到一种细菌莫拉氏菌，该细菌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检查。在没有有毒甲藻的情况下，贝类毒性增加期间，从海水中采集的不同粒径颗粒物中的PSP毒素分析表明，细菌大小的颗粒物中含有大量的PSP毒素，其分布与贝类和甲藻相似。在海水中也发现了莫拉氏菌。这些发现表明，海洋中存在可能与贝类毒性有关的PSP毒素产生细菌。这些也表明，细菌的毒素生产力在营养不良的条件下增加。因此，莫拉氏菌属在营养不良的条件下培养。在自然海水中培养10天后，其毒素产量增加，表明其在饥饿条件下产生毒素。从不同种类的有毒甲藻中筛选出PSP毒素产生菌。几乎所有的甲藻都能产生胞内产毒细菌。这些事实支持了胞内细菌是甲藻毒素产生所必需的观点。在有毒甲藻中发现的细菌种类对甲藻的菌株和种类具有特异性，显示这些细菌的广泛分布。在未发现甲藻水华的海域采集的双壳贝类中检测到PSP毒素，其来源似乎是细菌。

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.