Microbe may be missing link in the evolution of complex life

IT’S ONE OF the most fundamental questions in science: how did complex life evolve? Now, a team from Uppsala University in Sweden has moved one step closer to the answer after discovering a new group of microorganisms that represents a missing link in the evolution from simple to complex cells.

Dubbed Lokiarchaeota, or ‘Loki’ for short, the microbe was found in Loki’s Castle, a 2,350m-deep hydrothermal vent located between Norway and Greenland.

All organisms on Earth are either prokaryotes, such as bacteria, which have simple cells, or eukaryotes, such as mammals, which have more complex cells. However, as the two cell types are so different in composition, biologists have long wondered how one evolved from the other.

“The puzzle of the origin of the eukaryotic cell is extremely complicated, as many pieces are still missing. We hoped that Loki would reveal a few more pieces of the puzzle, but when we obtained the first results, we couldn’t believe our eyes.

The data looked spectacular,” says researcher Thijs Ettema. “By studying its genome, we found that Loki represents an intermediate form between the simple cells of microbes and the complex cells of eukaryotes.”

Despite having a very simple structure, the microbe was found to share many genes in common with eukaryotes. This suggests cellular complexity emerged in an early stage of evolution, the researchers say.

However, further investigation is required to determine what functions the genes perform. “We are just getting started. There is still a lot to discover, and I am convinced we will be forced to revise our biology textbooks in the near future,” says Ettema.