Quick Dips

Algae Alert

Researchers at Massey University and Nelson's Cawthron Institute have developed a new way to identify organisms appearing in algal blooms in seawater [Nov 1994]. Some microalgae produce natural poisons which can accumulate in shellfish, kill fin fish directly and cause neurological and other disorders in humans. These biotoxins can be ingested from food such as contaminated fish and shellfish, or taken in by direct contact with airborne sea spray.

Scientists monitoring biotoxins need to quickly identify the microalgae which produce them. Microscopic identification can be time-consuming, as considerable sample preparation and painstaking comparative observations of the detailed structure of cell wall material are needed.

Massey PhD student Lesley Rhodes, now with the Cawthron Institute, collaborated with Prof David Fountain to study the binding reactions of lectins, sugar-binding proteins that can be used to distinguish between cells of different species by their ability to recognise and bind to sugar-like molecules which make up part of the cell walls. Some lectins will strongly bind to some microalgal cells, others will not.

Lectins artificially joined to a fluorescent compound are used for the tests.

"When the lectin is chemically coupled to a fluorescent molecule, the presence or absence of binding can be seen using a fluorescence microscope so that algal cells which bind a particular lectin appear strongly coloured as they fluoresce," says Fountain. Such "fluorescent conjugated lectins" proved to be a fast and effective way of differentiating between closely related marine dinoflagellates, so similar in structure that they are difficult to tell apart under the microscope.