As the researchers report in an online prepublication of the scientific journal Nature, the microalga’s “trick” is genetic diversity. It has a particularly large so-called pan-genome which means that the unicellular algae share a certain set of common genetic information present in all strains.
Scanning microscope image of the calcite-forming algae Emiliania huxleyi. Photo: Gerald Langer, Alfred Wegener Institute
Satellite image of the mass development of coccolithophorides, a so called algal bloom, off Southwest England. Image: NASA
Without “Ehux“, as Emiliania huxleyi is fondly referred to by scientists, it would also probably be considerably warmer on the Earth. “The calciferous microalgae counteract climate change. Viewed in the long term, they absorb and fix considerable quantities of carbon from the atmosphere through photosynthesis and in the production of their calcified platelets”, says the biologist and co-author of the study Dr. Uwe John from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).
However, another characteristic of the microalga is even more interesting to him and his colleagues: “Ehux is able to adjust to a broad range of living conditions in the sea. It occurs in almost all regions of the oceans – from near the Equator to cooler latitudes, also here in the North Sea. However, we only now understand why this is”, says AWI algae researcher Dr. Klaus Valentin.
Uwe John, Klaus Valentin and their AWI colleagues Prof. Dr. Stephan Frickenhaus and Dr. Sebastian Rokitta are four of 75 scientists from the USA, Germany, Canada, France, United Kingdom, Belgium, and Chile, who together have succeeded in sequencing the genome of the calcified alga Emiliania huxleyi. “The genome, so to say, is the ”hard drive” of an organism. All properties are encoded there – how it looks, how it can adapt, how it competes with others. If we know the data on this hard drive, we can learn a great deal about what this organism can do and how it reacts to changes as a result of climate change, for example”, says Klaus Valentin.
The genome of the microalga was a great surprise for the scientists. “The Ehux genome is incredibly variable. 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. 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”, explains Uwe John.
During their work in the laboratory and on large computers, the researchers identified groups of genes which permit the calcified alga to prosper in water with a low phosphorous, iron or nitrogen content. Another gene set ensures that Ehux is not damaged even with an unusually high level of solar radiation. Uwe John: “This great genetic diversity will hopefully also permit the alga to cope with the current changes in the seas such as the rise in the water temperature and the carbon dioxide content.”
The genome data are now providing the AWI scientists the foundation for further detailed investigations. “We intend to understand how exactly the microalga reacts to the altered living conditions. For this purpose, we conduct gene expression studies, for example, which show how the increasing acidification of the ocean influences the metabolic processes inside the alga”, says Uwe John.
An insight into this area of Ehux genome research at the Alfred Wegener Institute is provided by Sebastian Rokitta‘s video introduction “Die Auswirkungen der Ozeanversauerung auf die Kalkalge Emiliania huxleyi“ on the AWI YouTube channel (link to the video: http://www.youtube.com/watch?v=rSW-F_Nm96M).Glossary:
The Alfred Wegener Institute conducts research in the Arctic and Antarctic and in the high and mid-latitude oceans. The Institute coordinates German polar research and provides important infrastructure such as the research icebreaker Polarstern and stations in the Arctic and Antarctic to the international scientific world. The Alfred Wegener Institute is one of the 18 research centres of the Helmholtz Association, the largest scientific organisation in Germany.
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