June 13, 2013
Bizarre Ehux Algae Adapts To Environment With Variable Genome
redOrbit Staff & Wire Reports - Your Universe Online
An international team of researchers has sequenced the genome of Emiliania huxleyi, a species of single-celled photosynthetic marine algae that they say is responsible for removing carbon dioxide from the air, supplying the oxygen we breath, and even forming the basis of marine food chains.The results of their work has just been published in the journal Nature and helps explain the tremendous adaptive potential and global distribution of this algae, which is smaller than a speck of dust and contains a shield of thin calcified platelets resembling the outside of a soccer ball.
A team of 75 researchers from a dozen different countries spent seven years mapping the genome, and found a set of core genes that have mixed with a separate set of variable genes. The authors reported that genetic diversity allows E. huxleyi (℠Ehux´ for short) to adapt to different environments, as part of its gene pool is dependent upon its geographic location and living conditions. It is the first algae in which scientists have detected this unique characteristic.
“The Ehux genome is incredibly variable,” said study co-author Dr. Uwe John and biologist with the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). “For example, if the genetic information of two humans is compared, an agreement of about 99 per cent is found. However, if, for example, we take two Ehux strains from different ocean regions, we find a degree of similarity of only 70 or 80 per cent. The rest of the genome differs.”
“This means that all of the algae possess a certain basic set of genes, the ℠core genome´, which is supplemented by different genes, i.e. is interchangeable to a certain extent, depending on the habitat of the algae,” he continued. “In the scientific world, we call this phenomenon 'pan-genome', which was only known from bacteria until we conducted our study. We have now demonstrated the pan-genome in a calcified alga for the first time.”
Dr. John and colleagues from the Department of Energy Joint Genome Institute (DOE JGI) sequenced the Ehux genome and compared it with the genetic information from other algal isolates, reporting their results in the June 12 edition of Nature. The strain sequenced by the researchers was isolated from the South Pacific and is the first reference genome for coccolithophores.
The project wound up taking the scientists longer to complete than originally predicted because of the complexity and size of the Ehux genome. They originally believed that it was an estimated 30 million bases, but the genome wound up being more than four times that size — approximately 141 million bases. Sequencing efforts of Ehux, which is part of the third most abundant group of phytoplankton, was first proposed by researchers back in 2002.
“Ehux is the dominant bloom forming coccolithophore and is abundant in oligotrophic oceans — those that have little to sustain life — so they exert a large effect on global carbon cycling,” wrote lead investigator Betsy Read, a professor of biological sciences at California State University.
“Until now, the underlying mechanisms for the considerable physiological and morphological variationsbetween isolates have been elusive. Evidence we present indicates that this capacity can be explained in part by its pan-genome, the first of its kind reported for what was thought to be a single microbial eukaryotic algal species.”
Their work could provide clues as to the future of the world´s climate, as Ehux could adapt under increasingly acidic changes, leading to a change in the way it interacts with and impacts the carbon cycle. Sequencing this genome also brings scientists closer to understanding evolution as well as how organisms change in order to exploit their environments. Finally, the researchers report that it could lead to medical breakthroughs because of the anti-microbial, anti-fungal, anti-parasitic and anti-tumor properties of some of Ehux´s metabolites.