Ecological roles of vitamin B_<12> binder produced by microorganisms on the growth of red tide phytoplankton

研究<12>了细菌和浮游植物产生的维生素B_结合剂对赤潮浮游植物生长的生态学作用。主要研究结果如下：1.发现赤潮浮游植物中肋骨条藻、米氏裸藻和赤潮异弯藻产生维生素B_<12>结合剂。赤潮血吸虫将大部分分泌到培养基中，而其它血吸虫则将部分分泌到细胞中.海水中约60%的异养细菌能够产生并分泌B_<12>binder.发现<12>由赤潮红球藻产生的B_结合剂对游离B_具有高亲和力<12>：解离常数为52.8 ng/l。粘结剂对需要游离硼的浮游植物的生长有非特异性的抑制作用<12>.在天然富营养化海水中，B_<12>结合剂的分解与其产生是平行的。B_ binder的产生<12>是细菌和浮游植物共同作用的结果，而B_binder的分解则是细菌本身作用的结果，表明<12>微生物产生的B_ binder能抑制需B_<12>binder的浮游植物的生长，并影响需B_<12>binder与其它需B_binder的竞争。

Ecological roles of vitamin B_<12> binder produced by bacteria and phytoplankton on the growth of red tide phytoplankton were studied. The results were summarized as follows :1. Red tide phytoplankton, Skeletonema costatum, Gymnodinium mikimotoi, and Heterosigma akashiwo were found to produce vitamin B_<12> binder. H.akashiwo secreted most of the binder produced into the medium, but the others kept ones into their cells.2. About 60 per cent of total heterotrophic bacteria in seawater was able to produce and excrete B_<12> binder.3. The B_<12> binder produced by H.akashiwo was found to have a high affinity to free-B_<12> : the dissociation constant was 52.8 ng/l. The binder inhibited non-specifically the growth of phytoplankton requiring free-B_<12> for their growth.4. In natural eutrophic seawater, B_<12> binders decomposed in parallel with their production. The production of B_<12> binder was due to both bacteria and phytoplankton, while the decomposition was due to bacteria as such.Present results revealed that B_<12> binder produced by microorganisms could inhibit the growth of B_<12>-requiring phytoplankton and also influence the competition between B_<12>-requirer and the others.