Effects of intracellular bacteria on the growth of the red tide flagellate Heterocapsa circularisquama

在日本中部和西部的海湾，有害的甲藻Heterocapsa circuliquama引起了大规模的赤潮，导致了大量的自然和养殖双壳类的死亡。细菌存在于细胞内，偶尔也存在于它们的食物泡中。这些细菌可能对藻类的生理生态有一定的影响。研究了生长量与生长量之间的相互关系。通过实验室培养实验，对环孢类真菌和胞内细菌进行了初步研究。这五种藻株（Y、UA、UB、A和I）分离自日本西部的不同地点。每种菌株培养物都是用精心制作的微量移液器洗涤液建立的，然而，每种培养菌株都含有细胞内和细胞外细菌群体，分别命名为Yb、Uab、Ubb、Ab、Ib。胞外细菌可能是从藻类细胞中释放出来的。每种藻类培养物中的细菌细胞总数在藻类指数生长期期间增加。根据最终的细胞产量，将5个菌群分为Yb和Uab、Ab和Ib、Ubb 3个菌群。细菌的生长依赖于活的藻类细胞。对5株H.在5种不同光照强度和5种不同培养基强度条件下，对从UB菌株中分离的有菌环孢菌菌株和无菌环孢菌菌株进行了比较。与无菌藻株相比，含胞内细菌藻株的生长和存活没有明显优势。然而，细胞内细菌可能有助于H。在生活史、毒素产生等方面与圆蚧种群有一定的关系。

In the embayments of central and western Japan, the harmful dinoflagellate Heterocapsa circularisquama has caused large scale red tides, which brought on mass mortalities to both natural and cultured bivalves. The alga has bacteria inside the cells and occasionally in their food vacuoles. It is suspected that these bacteria give some effects on the algal ecophysiology. The mutual relationships were investigated between the groth of H. circularisquama and intracellular bacteria with laboratory culture experiments. The five algal strains (Y, UA, UB, A, and I) were isolated from different locations of western Japan. Each strain culture was established with elaborate micro-pipette washings, nevertheless, each culture strain contains intracellular and extracellular bacterial populations, designated as Yb, Uab, Ubb, Ab, Ib, respectively. The extracellular bacteria were presumably released from the algal cells. The total number of bacterial cells in the each algal culture increased during the algal exponential growth phase. According to the final cell yields, the five bacterial populations are divided into three groups, Yb and Uab, Ab and Ib, and Ubb group, respectively. The bacterial growth depended on live algal cells. Growth experiments were carried out on the five H. circularisquama strains with bacteria and a bacteria-free strain, established from the dtrain UB, under the conditions of five different light intensities and in five different strengths of medium. There appeared to be no significant advantages for the growth and survival of the algal strains with intracellular bactera, as compared with the bacteria-free strain. Intracellular bacteria, however, might contribute to H. circularisquama populations in some aspects such as life cycle and toxin production.