Sodium channel blocking (SCB) activity and transformation of paralytic shellfish toxins (PST) by dinoflagellate-associated bacteria

Abstract

Bacteria associated with toxic algae in culture have been implicated in the enhancement of algal toxin production and in auto-toxigenesis, with taxon specificity of the bacteria suggested to be important in their association with the algae. In this study, bacteria isolated from toxic and non- toxic dinoflagellates have been examined for both their potential to produce sodium channel block- ing (SCB) toxins, as ascertained by the mouse neuroblastoma assay, and their ability to biotransform paralytic shellfish toxins (PST) using high-performance liquid chromatography (HPLC). Toxigenic bacteria were found to belong to the α- and γ-Proteobacteria. Bacteria capable of SCB activity were present in PST-producing Alexandrium tamarense and A. lusitanicum cultures, while the bacterial flora isolated from a non-toxic A. tamarense strain did not appear to demonstrate this trait. A dis- parate population of the bacterial flora associated with non-PST-producing Scrippsiella trochoidea also demonstrated SCB activity. Some bacteria from all the dinoflagellates examined were capable of transforming PST, with possible mechanisms including oxidase activity with transformation of gonyautoxins GTX 2/3 to GTX 1/4, reductive elimination as demonstrated by the transformation of GTX 1/4 to GTX 2/3, and further unknown pathways. Noticeably, there was little overlap between bacteria demonstrating SCB activity and those that were able to modify PST, indicating that biosyn- thesis of SCB toxins and catabolism of PST may not be related in these bacterial isolates.