Eukaryotic Cell Found That Lacks Mitochondria

Eukaryotic cells make up complex organisms like humans and trees and can exist as single-celled organisms such as amoebas and paramecia. These cells contain a nucleus by definition as well as a number of organelles (”little organs”) that carry out specific functions for the cell, like protein synthesis. Although all eukaryotes were thought to contain organelles known as mitochondria, which serve as “powerhouses” and produce an essential energy-carrying molecule known as ATP, scientists have discovered a single-celled eukaryote that lacks these critical mitochondria—an unprecedented finding.

While sequencing the genome for Monocercomonoides, a group of organisms related to Giardia and Trichomonas, scientists were surprised to find no evidence of mitochondrial DNA nor of the proteins necessary for the mitochondria to exist. These organisms live in low-oxygen environments, and it seems that they have been able to survive without mitochondria, thanks to an energy system used by bacteria. The discovery raises fascinating questions about the evolution of these unique eukaryotes and rewrites previous assumptions about the requirements for eukaryotic life.