Great South Bay during a harmful algal tidal bloom. (Photo: Suffolk County Department of Health Services)
Genome of harmful algal bloom species discovered
Wednesday, February 23, 2011, 15:30 (GMT + 9)
A team of researchers including scientists from the US Department of Energy (DOE) Joint Genome Institute (JGI) recently revealed the first complete and annotated genome sequence of the harmful algal bloom (HAB) species Aureococcus anophagefferens.
The findings were published online this week in the Proceedings of the National Academy of Sciences in the article "Niche of harmful alga Aureococcus anophagefferens revealed through ecogenomics."
"Harmful algal blooms are not a new phenomenon, although many people may know them by other names such as red tides or brown tides," said Christopher J Gobler, PhD, Associate Professor of the School of Marine and Atmospheric Sciences at Stony Brook University and leader of the study. "These events can harm humans by causing poisoning of shellfish and can damage marine ecosystems by killing fish and other marine life."
And the problem is worsening. "The distribution, frequency and intensity of these events have increased across the globe and scientists have been struggling to determine why this is happening," he noted, reports NewsWise.
|Aureococcus anophagefferens cells. (Photo: Chris Gobler, Stony Brook University)
By sequencing its genome, the scientists can now analyse its "parts list" for data that will help them understand Aureococcus' ability to gather CO2, survive in disparate marine environments, exploit selenium in its proteins and outgrow many of its counterparts.
Aureococcus’s 56-million base pair genome was sequenced by the DOE JGI from a culture isolated sample taken from the shores of Long Island, New York -- one of the areas most affected by the microalga since it first appeared there 25 years ago.
In cases when billions of Aureococcus cells gather together, the organism outcompetes the other regional marine phytoplankton, thereby damaging the food chains in marine ecosystems and economically harming the local shellfish industry.
Economic losses ascribed to this and other HAB incidences in the country in the last 10 years have been estimated at USD 1 billion.
"Compared to [Ostreococcus and cyanobacteria] inhabiting the same estuaries, Aureococcus, which outcompetes them, shows genome-encoded advantages to benefit from alternative nutrients, survive under variable light conditions, and encode the largest number of selenoproteins (which use the trace element selenium to perform essential cell functions) known to date," commented DOE JGI's Igor Grigoriev.
This photosynthetic microalga is well-adapted to low light, for instance, and can thus survive for long periods in darkness. The genomic study showed that Aureococcus contained 62 light-harvesting genes compared to its competitors, which had on average 24 of these genes.
"For decades, scientists have been trying to understand why this species blooms, when it blooms, how it is able to dominate when there are so many other competing species in the water with it,” said Don Anderson, a senior scientist at Woods Hole Oceanographic Institution (WHOI) who has studied harmful algal blooms for decades and is a diligent promoter of research efforts in the field. “With this new genomic data we have a new approach.”
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By Natalia Real