Smaller than a speck of dust, Emiliania huxleyi plays an outsized role in the world’s seas. Ranging from the polar oceans to the tropics, these free-floating photosynthetic algae remove carbon dioxide from the air, help supply the oxygen that we breathe, and form the base of marine food chains. When they proliferate, their massive turquoise blooms are visible from space.
Now scientists have discovered one of the keys to E. huxleyi‘s success. A seven-year effort by 75 researchers from 12 countries to map its genome has revealed a set of core genes that mix and match with a set of variable genes that likely allows E. huxleyi, or Ehux, to adapt to different environments. Their results are described in the latest issue of Nature.
Over generations, the exchange of material within Ehux’s so-called “pan-genome” has allowed it to evolve in far-flung places. “In the sea, we thought that only bacteria were shuffling around their genes in this way so it was a real shock to see that Ehux was doing the same thing,” said senior co-author of the study Sonya Dyhrman, a microbial oceanographer at Columbia University’s Lamont-Doherty Earth Observatory.
Like all phytoplankton, Ehux harvests sunlight from the upper layer of the world’s oceans. But it sets itself apart by building armor-like plates of chalk, or coccoliths. It lives mostly in cold, nutrient-rich waters but also thrives at the warm, nutrient-poor equator. Its variety of shapes and sizes, and the diverse places it calls home, hint at its extreme versatility.
Two-thirds of Ehux’s genes are shared among all strains. This core genome allows Ehux to thrive under low levels of phosphorus and iron, elements key to life but in short supply in the ocean. The remaining third of its genes are present in one but not all strains. In this variable gene pool are those that allow Ehux to use varying forms of nitrogen, another relatively scarce element in the sea. This flexibility likely allows it to adapt to changing environmental conditions.
Read more at: Phys.org