DNA probes

What are DNA Probes?
Little more than a decade ago, toxic phytoplankton monitoring with DNA probes was still in the realm of science fiction. Today it is a reality. Probes for some key micro-algae are already in commercial use and ultimately DNA probes could become a major HAB monitoring tool.

What exactly are they?
DNA probes have been in use for more than a decade in medicine and dentistry, but they have only recently been developed with the aquaculture industry in mind. The DNA of a selected micro-alga is sequenced, and the sequence of nucleotides that makes up its genetic code is compared with that of other related algae using readily available computer software packages. Unique nucleotide "signatures" (usually between 15 and 50 nucleotides) are selected to develop into probes. The ribosomal RNA (rRNA) of the cell is targeted because it is abundant in cells and so good recognition, or a good "hit", is ensured. The probes will have some "tag", for example fluorescein, attached for easy recognition of a positive assay. The probes can be prepared for a number of different assay systems, but require intensive trialling to ensure there is no cross-reactivity with other micro-algae species.
Pseudo-nitzschia and Alexandrium whole cell format DNA probes are now used routinely in New Zealand's phytoplankton monitoring programmes as an aid to risk management decision-making, and the monitoring laboratory (Cawthron Institute) is approved by International Accreditation New Zealand (recognised under ISO17025).

How are they used?
Identification of micro-algae to species level is vital so that shellfish growers, and health and industry officials, can make safe and economically sound harvesting decisions.
Standard phytoplankton monitoring methods involve identifying toxic species in a water sample and counting them. It is labour intensive and requires expert training in the recognition of the critical algae. In some case scanning electron microscope preparation of samples can be required to differentiate species. This can be expensive and cause delays. DNA probes offer an exciting and rapid alternative

http://www.geneprobes.org/whatare.htm