Studies on Bacteria Which Produce Paralytic Shellfish Toxins.

在大船渡湾，在没有有毒甲藻的情况下，贝类的毒性经常会增加。这一现象表明存在未知的致病生物体(S)。最近，我们发现了一株细菌--莫拉氏菌。从塔玛亚历山大藻分离得到的毒素(PSP毒素)能产生麻痹性贝类毒素。从而研究了该细菌与贝类毒性之间的联系。在贝类毒性增加期间，对海水中不同大小颗粒物中的PSP毒素进行了分析，结果表明，细菌大小的颗粒物中含有大量PSP毒素，其分布与贝类和甲藻相似。Moraxella sp.在海水中也检测到了。这些发现表明，海洋中存在PSP毒素，产生细菌，可能与贝类毒素有关。这些也表明，在营养不良的条件下，细菌的毒素产量会增加。因此，Moraxella sp.是在营养不良的条件下培养的。在天然海水中培养10天后，其产毒量增加，表明其在饥饿条件下产生毒素。在不同种类的有毒甲藻中筛选出产生PSP毒素的细菌。几乎所有的甲藻都能产生产毒素的胞内细菌。这些事实支持了这样一种观点，即细胞内的细菌是甲藻毒素产生所必需的。在有毒甲藻中发现的细菌种类既有菌株所特有的，也有甲藻物种所特有的，表明这些细菌分布广泛。在从没有甲藻开花的地区采集的双壳类中发现了似乎来自细菌的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.