A fluorescence microscopy tool may help screen shellfish for dinoflagellates that produce toxins. (Photo: Stock File)
New tool may brighten future of toxin screening in shellfish
Monday, October 11, 2010, 23:50 (GMT + 9)
US scientists have come up with a fluorescent probe that could offer a tool for real-time toxin screening in shellfish and help eradicate seafood related food-poisoning.
Some dinoflagellates, organisms typically found in sea water, can be toxic and are linked to injurious algae and bacteria buildup, which can lead the way to toxins moving into shellfish tissue, thereby putting food safety in serious danger.
Although it has been considered that symbiotic bacteria are important in the biosynthesis of toxins from dinoflagellates, this toxin-bacteria interaction has only now been established, reports the Royal Society of Chemistry.
Michael Burkart et al at the University of California at San Diego (UCSD) have worked to create a fluorescence microscopy tool to screen shellfish for dinoflagellates that produce toxins.
His team fluorescently labelled a protein taken up by the marine cells that biosynthesise the toxin, okadaic acid. In vivo studies have demonstrated that the samples generating the toxin show up in fluorescent blue under the microscope.
The same samples that gave a positive response to the probe also gave signs of symbiotic bacteria in their cell walls, which proves the toxin-bacteria association.
Burkart's assay is therefore capable of selecting mussels that carry live toxin producing dinoflagellates at various stages of infection, by counting the number of cells that glow. Imaging shellfish going through dinoflagelate infection identifies okadaic acid much faster than current methods that only detect the dinoflagellates once they are completely absorbed into the shellfish tissue.
This discovery has “the beginnings of a potentially useful surveillance tool for public health,” said Jon Clardy, a pharmacology researcher at the Harvard Medical School in Cambridge, US.
He was mostly surprised to find that the bacteria play a role in the biosynthesis of okadaic acid and are possibly related to dinoflagellate toxins.
“The biosynthesis of these compounds has been untouchable because of the enormous size of dinoflagellate genomes, which are much larger than human genomes, and the lack of genetic systems, which has frustrated commonly used approaches,” he commented.
Burkart said that if this method can be used with an automated system, it could be a useful screening tool for the aquaculture sector.
“One could imagine a mobile phone application that would let you see if your crop or plate of oysters is safe for consumption. There is a tremendous potential in visual methods for food quality screening and its merge with the modern digital devices and networks,” he envisioned.
By Natalia Real