It's common knowledge that in eukaryotic cells, which are cells that have a nucleus and organelles enclosed in membranes, it's the mitochondria that is responsible for powering the cell. These kinds of cells need a lot of energy to support the functions the perform and most of it is thought to come from the mitochondria that produce ATP, a specific protein that powers the cell. Recently though, scientists at the University of Prague discovered an organism that has no mitochonria. It's found in the gut biome of chinchillas and since there isn't much oxygen, it's thought that the mitochondria was lost in the evolutionary process.
Called monocircomonoides, the organism is powered on a sulphur based system that gives the gut biome the energy to digest food and turn it into fuel. The team in Prague believes there are other forms of these kinds of organisms that also lack mitochondria and will be expanding their research to see if they can connect other biomes with the protists they have found so far.