Application of ribosomal RNA-targeted probes to detect Pseudo-nitzschia multiseries and P. pungens in Atlantic Canadian waters

At least 7 species of the pennate diatom Pseudo-nitzschia are producers or suspected producers of the neuritoxin domoic acid, causative agent of Amnesic Shellfish Poisoning. Many other Pseudo-nitzschia species are non-toxic, but are difficult to distinguish from among themselves or from the toxic species. Electron microscopy is most often used to identify Pseudo-nitzschia species. This is a laborious and time-consuming procedure that requires expensive instrumentation. Oligonucleotide (ribosomal RNA)-targeted probes have been developed to distinguish among 7 Pseudo-nitzschia species found in coastal waters of California. They take advantage of unique large unit ribosomal RNA gene sequences, acting as ‘signatures’, for each Pseudo-nitzschia species. This paper documents that these nucleotide probes are also capable of detecting eastern Canadian species of Pseudo-nitzschia. Also examined are if differences in cell physiology in cultures affect the amount of labelling by these probes.