Whole cell DNA probes are now available for a wide range of microalgae, with probes currently being developed for species in the genus Karenia (formerly known as Gymnodinium). These species produce a range of toxic compounds including the neurotoxic brevetoxins. Probes are already available for Karenia mikimotoi. Sandwich hybridisation probes are also being developed for species in this group.

Contacts for obtaining whole cell format DNA probes are:

"Oligos"
(for ordering probes)
web: www.oligosetc.com

"Invitrogen"
web: www.invitrogen.com

and for probes in Sandwich Hybridisation format:

Jason Ray
ORCA
(for ordering sandwich hybridisation assay plates and analysers)

email: orcaresearch@yahoo.com

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Probes and Pfiesteria

PCR based probe assays have also been developed for a range of microalgae species including Pfiesteria piscicida and P. shumwayae. To find out more read

Rublee, P.A., J.W. Kempton, E.F. Schaefer, C. Allen, J. Harris, D.W. Oldach, H. Bowers, T. Tengs, J.M. Burkholder, and H.B. Glasgow (2001) Use of Molecular Probes to Assess Geographic Distribution of Pfiesteria Species. Environmental Health Perspectives 109:765-774 full article- pdf format
More information on Pfiesteria can be found at www.dnr.state.md.us/
pfiesteria/ and
www.pfiesteria.org

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Single cell detection

New methods based on single cells are being developed and will be demonstrated at the workshop to be held in Bremerhaven, Germany in April 2002 (see workshops and conferences).

New methods of biotoxin detection at Cawthron Institute include routine testing for marine biotoxins using LC-MS (visit the Cawthron site to find out more). Recent work linking DNA probes with biotoxin analyses by LC-MS has led to the discovery of the production of new compounds by micro-algae.

An unexpected bonus to the success of the DNA probes has been the development of immunoassays to biotoxins. Domoic acid, which causes amnesic shellfish poisoning or ASP, is easily detected by immunoassay. Dr Ian Garthwaite, AgResearch, Hamilton has developed suitable antibodies in sheep. (These act much as antibodies in the human immune system do, by binding to specific harmful microbes.)

The immunoassay has been tested on the microalgae that produce domoic acid, the Pseudo-nitzschias, and we now have a good idea of the likely level of toxin per cell for each Pseudo-nitzschia species. The result is that not only can shellfish harvesters be warned of a bloom of potential harmful Pseudo-nitzschias, but also of how toxic the bloom is likely to be.

Pseudo-nitzschias with DNA Probe