Tn5 MUTAGENESIS OF PSEUDOMONAS STUTZERI SF/PS, A BACTERIUM ASSOCIATED WITH ALEXANDRIUM LUSITANICUM (DINOPHYCEAE) AND PARALYTIC SHELLFISH POISONING

It is becoming increasingly clear that bacteria can play an important role in the toxin and population dynamics of harmful algal bloom (HAB) events. In this paper, we document protocols and strategies that can be used to identify bacterial genes involved in either the production of toxic compounds and/or the establishment and maintenance of relationships between bacteria and algae. The protocols we tested involved transposon mutagenesis and complementation with broad-host-range plasmids. We tested six bacterial strains thought to be involved, either directly or indirectly, in the production of toxins associated with paralytic shellfish poisoning (PSP). Five strains were resistant to transformation under the growth conditions used. However, a single strain, Pseudomonas stutzeri SF/PS, was readily transformed when grown under appropriate conditions. This bacterium has been shown to accumulate PSP toxins and to increase toxin production when added to axenic cultures of a toxic dinoflagellate, Alexandrium lusitanicum . We conclude that a transposon mutagenesis strategy can be used to identify genes involved in HAB events.