Fatty acid composition of bacteria associated with the toxic dinoflagellate Ostreopsis lenticularis and with Caribbean Palythoa species.

The fatty acid composition of a Pseudomonas sp. (Alteromonas) and its host, the dinoflagellate Ostreopsis lenticularis, vectors in ciguatera fish poisoning, has been studied. The major fatty acids in O. lenticularis were 16:0, 20:5n-3, and 22:6n-3, but 18:2n-6, 18:3n-3, and 18:n-3 were also identified. In contrast to other dinoflagellates, 1 8:5n-3 was not detected in O. lenticularis. Even-chain fatty acids such as 9-16:1, 11-18:1, and 13-20:1 predominated in the Pseudomonas sp. from O. lenticularis, but 1 6-20% of (E)-11-methyl-12-octadecenoic acid was also identified. The chirality of the latter was confirmed by total synthesis (28% overall yield) starting from oxacyclotridecan-2-one. The fatty acid compositions of two other Pseudomonas species, from the palytoxin-producing zoanthids Palythoa mamillosa and P. caribdea, were also studied and were similar to that of the Pseudomonas sp. from O. lenticularis. The possibility of using some of these fatty acids as chemotaxonomic lipids in identifying marine animals that consume toxic dinoflagellates or zoanthids is discussed.

The fatty acid composition of a Vibrio alginolyticus associated with the alga Cladophora coelothrix. Identification of the novel 9-methyl-10-hexadecenoic acid.

The fatty acid composition of a new strain of Vibrio alginolyticus, found in the alga Cladophora coelothrix, was studied. Among 38 different fatty acids, a new fatty acid, 9-methyl-10-hexadecenoic acid and the unusual 11-methyl-12-octadecenoic acid, were identified. Linear alkylbenzene fatty acids, such as 10-phenyldecanoic acid, 12-phenyldodecanoic acid and 14-phenyltetradecanoic acid, were also found in V. alginolyticus. The alga contained 43% saturated fatty acids, and 28% C16-C20 polyunsaturated fatty acids of the n-3 and n-6 families.

Role of associated bacteria in growth and toxicity of cultured benthic dinoflagellates.

Clonal cultures of the toxic benthic dinoflagellate Ostreopsis lenticularis isolated from the coastal waters of southwest of Puerto Rico show peak toxicities during the stationary phase of growth, correlated with significant increases in bacteria directly associated with these cells. The specific toxicity (MU/mg) of dinoflagellate extracts in control cultures increased 340% during the static phase of culture growth, while those cultures treated with antibiotics that inhibit prokaryote protein synthesis showed no significant increase in toxicity during this phase of culture growth. There was a significant decrease in the diversity of dinoflagellate associated bacterial strains in antibiotic treated cultures. These data indicate that associated bacteria play a role in toxin production by dinoflagellate-bacteria consortia when grown in laboratory culture.

Associated bacterial flora, growth, and toxicity of cultured benthic dinoflagellates Ostreopsis lenticularis and Gambierdiscus toxicus.

The growth, toxicity, and associated bacterial flora of 10 clonal cultures of the toxic benthic dinoflagellates Ostreopsis lenticularis and Gambierdiscus toxicus isolated from the coastal waters of southwest Puerto Rico have been examined. Clonal cultures of O. lenticularis grew more rapidly and at broader temperature ranges than those of G. toxicus. All five Ostreopsis clones were toxic, while only one of the five Gambierdiscus clones was poisonous. The degree of toxicity among poisonous clones was highly variable. The number of associated bacterial genera and their frequency of occurrence were quite variable among clones of both dinoflagellate genera. Bacterial isolates represented six genera (Nocardia, Pseudomonas, Vibrio, Aeromonas, Flavobacterium, and Moraxella) in addition to coryneform bacteria. Extracts of dinoflagellate-associated bacteria grown in pure culture were not toxic. Gambierdiscus clones were characterized by the frequent presence of Pseudomonas spp. (four of five clones) and the absence of coryneforms. In O. lenticularis, only one of five clones showed the presence of Pseudomonas spp., and Moraxella sp. was absent altogether. Detailed analyses of toxicity and associated microflora in a selected Ostreopsis clone, repeatedly cultivated (four times) over a period of 160 days, showed that peak cell toxicities developed in the late static and early negative culture growth phases. Peak Ostreopsis cell toxicities in the stationary phase of culture growth were correlated with significant increases in the percent total bacteria directly associated with these cells. Changes in the quantity of bacteria directly associated with microalgal cell surfaces and extracellular matrices during culture growth may be related to variability and degree of toxicity in these laboratory-cultured benthic dinoflagellates.