Cell Powerhouses Evolved from Parasitic Bacteria

It turns out that parasitic bacteria may be to blame for the eventual evolution of mitochondria, the powerhouses of animal and plant cells. Scientists have found that these bacteria first acted as energy parasites before becoming beneficial.

The origin of mitochondria began about 2 billion years ago. This event helped spur further evolution as it powered animal and plant cells. Yet very little is known about the circumstances surrounding the origin of mitochondria, which is why scientists decided to take a closer look.

The researchers used next-generation DNA sequencing technologies in order to decode the genomes of 18 bacteria that are close relatives of mitochondria. This allowed them to reconstruct the gene content of mitochondrial ancestors. In the end, they predicted that the first "mitochondria" was actually a parasite that stole energy in the form of ATP from its host, which is completely opposite to the current role that it plays.

"We believe this study has the potential to change the way we think about the event that led to mitochondria," said Martin Wu, the lead author of the new study, in a news release. "We are saying that the current theories-all claiming that the relationship between the bacteria and the host cell at the very beginning of the symbiosis was mutually beneficial-are likely wrong. Instead, we believe the relationship likely was antagonistic-that the bacteria were parasitic and only later became beneficial to the host cell by switching the direction of the ATP transport."

The findings reveal a bit more about the evolution of mitochondria. This, in turn, can tell researchers about the evolution of animal and plants in general. By looking at evolution at a cellular basis, the scientists can expand and better learn about this process over our Earth's history.

The findings are published in the journal PLOS One.