A hydrothermal vent found deep in the ocean. Picture taken by NOAA expedition in 2004, licensed under public domain.

In the 1970s, a scientist named Carl Woese compared all of cellular life and divided it into three categories: bacteria (such as E.coli), archaea (microbes most famous for living in extreme temperatures, though they are found in other environments), and eukarya (animals and plants). All eukaryotes share the same complexity in their cells. Because eukaryotic cells are relatively new compared to those of bacteria and archaea, scientists have long wondered how and when eukaryotes evolved. Recently, scientists discovered a species of archaea called Lokiarchaeum that may provide a link to the origin of eukaryotic cells. The DNA of this particular microbe was discovered in sediment samples taken near a hydrothermal vent in the Arctic Ocean. After analyzing the DNA, researchers found that the microbe contains instructions for building cellular compartments and skeletons, all of which are associated with eukaryotic cells.

Though the results are very exciting, they are also preliminary. Lokiarchaeum are extremely sensitive to environment and die after they leave the sediment. Therefore, the researchers do not know the size of the cells or how they function. The residual DNA of the Lokiarchaeum suggests that they have a cellular skeleton and special compartments, but there is no way to know for certain until the microbe is cultivated and observed in the lab.

Aknowledgements: Many thanks to Heather Olins and Holly Elmore, graduate students in the Organismic and Evolutionary Biology Department at Harvard University, for providing their expertise and insight into the topic.

Managing Correspondent: Haley Manchester

Original Article: Complex archaea that bridge the gap between prokaryotes and eukaryotes – Nature

Media Coverage: Under the Sea, a Missing Link in the Evolution of Complex Cells – New York Times

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