A recent study has discovered a microscopic eukaryote that appears to have eliminated its mitochondria, joining an exclusive club of organisms that can thrive without these essential energy-producing structures. Skoliomonas litria is the first free-living eukaryote found to have lost its mitochondria.
Mitochondria are often referred to as the powerhouse of the cell, generating energy through the process of cellular respiration. Their acquisition is considered a key event in the evolution of eukaryotes, which include animals, plants, and fungi.
However, some eukaryotes have been found to survive without typical mitochondria. Monocercomonoides, discovered in 2016, is one such example. This commensal organism lives in oxygen-poor environments and absorbs nutrients from its surroundings. It has adapted to the powerhouse-free life by “borrowing” genes from neighboring bacteria to fulfill other essential mitochondrial functions.
The newly studied Skoliomonas genus belongs to the phylum Metamonada, which includes Monocercomonoides. The study analyzed five recently discovered metamonads that are free-living, including species from two genera: Skoliomonas and Barthelona.
Phylogenomic analysis revealed that both genera form their own clade, named “BaSK.” BaSKs display a level of MRO reduction not typically seen in free-living metamonads. They have acquired systems to replace the iron-sulfur cluster system, which is vital for assembling groups of iron and sulfur molecules needed by cellular proteins.
One specimen stood out: Skoliomonas litria appears to have no mitochondrial pathways at all. If confirmed, it would be the first example of a free-living metamonad to have lost its organelle.
More research will be needed to determine how and where S. litria makes its ATP without oxygen. However, this discovery suggests that there may be an exception to every rule in biology. The study is published in Nature Communications.
Source: https://www.iflscience.com/single-celled-organism-may-be-first-free-living-eukaryote-without-mitochondria-ever-discovered-75624