Scientists Discover First Ever Eukaryotes Without a Mitochondria
For decades, scientists believe that eukaryotes can't survive without mitochondria, the powerhouse of the cell. A team of researchers led by evolutionary biologist Anna Karnkowska, a postdoc, and her adviser, Vladimir Hampl, of Charles University in Prague discovered a microbe that can survive without mitochondria.
"They're part of the definition of eukaryotic cell," Karnkowska told the Washington Post. "If you open a biology textbook to a picture of a eukaryotic cell, that's what you'll see."
For the study, researchers used the 454 whole-genome shotgun sequencing methodology to generate a draft genome sequence of the oxymonad Monocercomonoides, which belongs to a group of microbes that scientists believe had lost their mitochondria.
Their genome sequence revealed no signs of mitochondrial genes in the microbe. Further examination also showed that Monocercomonoides are lacking all the key proteins that enable mitochondria to function.
Monocercomonoides is a single-celled organism that lives in the intestines of chinchilla hosts. Researchers suggest that this kind of microbes don't due to the abundance of nutrients and scarcity of oxygen in their environment. Oxygen is required for the energy production in the mitochondria. Due to the near absence of oxygen in their environment, Monocercomonoides is more likely to enzymes in its cytoplasm to break down food and produce energy.
Other important function of mitochondria is the synthesis clusters of iron and sulfur that are essential helpers for a variety of proteins, but these organisms, cope up with the absence of mitochondria by borrowing some bacterial genes that perform the same function.
"It's a very solid paper experimentally," said evolutionary genomicist B. Franz Lang of the University of Montreal in Canada, in a statement. "If you'd like me to bet, I'd give them 90% probability that they are correct."
According to the researchers, their findings provide better understanding in the evolution of single-celled organism. It also suggests that there might be other eukaryotes that are still striving even with the absence of their powerhouse.