Direct contact between Pseudo-nitzschia multiseries and bacteria is necessary for the diatom to produce a high level of domoic acid
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Pseudo-nitzschia multiseries loses most of its ability to produce domoic acid when it is cultured axenically. However, domoic acid production recovers when bacteria from the original culture are reintroduced to axenic cultures, indicating a bacterial association with domoic acid production in this species. In order to determine the role of bacteria in domoic acid production, an axenic strain prepared from a nonaxenic strain of P. multiseries was inoculated into media in cellophane tubes, which were then placed in a bottle containing the original nonaxenic culture. Both strains showed characteristic domoic acid production similar to that previously observed. Domoic acid level in the cells of the axenic strain in the tubes was much smaller than that of the cells outside the tubes. These results show that direct contact between living bacteria and P. multiseries is necessary for producing high levels of domoic acid in P. multiseries.
KeywordsCo-culture of axenic and nonaxenic strains Domoic acid Pseudo-nitzschia multiseries
This study is partly supported by a grant-in-aid from the Ministry of Education, and a grant for the Cooperative Research Program of the School of Fisheries Sciences, Kitasato University.
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