rRNA sequences reflect the ecophysiology and define the toxic cyanobacteria of the genus Nodularia

Nodularia, a member of the order Nostocales, is a bloom-forming filamentous cyanobacterium that possesses the ability to form toxic blooms. The toxin produced by Nodularia, nodularin, is a hepatotoxin, similar in structure to the heptapeptide toxin microcystin. Twenty-one strains of Nodularia, repre senting the species Nodularia spumigena, Nodularia harveyana and Nodularia sphaerocarpa, were analysed for toxin production by protein phosphatase inh ibition assay and sequenced over the 16S rDNA region. Phylogenetic analysis of Nodularia 16S rDNA sequences found that Nodularia clustered into two ma in groups. An IV. spumigena cluster was distinct from the benthic species A l. harveyana and Al. sphaerocarpa. There was no distinction between strains isolated from globally diverse locations. Nodularin-producing species were restricted to the single, evolutionally distinct cluster of N. spumigena. This observation has enabled the design of a specific 16S rRNA PCR for the rapid detection of nodularin-producing strains. Alignment of 16S rDNA seque nces from toxic and non-toxic Nodularia with other members of the cyanobact eria allowed the design of both Nodularia generic and toxic Al. spumigena-s pecific primers.