mitochondrialike

Mitochondrial-like refers to organelles that are derived from mitochondria but are reduced in function or genome compared with canonical mitochondria. The term is commonly used for mitosomes and hydrogenosomes, which are collectively known as mitochondrion-related organelles (MROs). These organelles are found in diverse protists and some fungi, especially those living under anaerobic or microaerophilic conditions.

Many mitochondrial-like organelles retain some features of mitochondria, such as a double-medial membrane and protein import systems, but they often lack a complete set of mitochondrial pathways. Mitosomes, for example, are highly reduced and typically do not perform oxidative phosphorylation or contain a functional electron transport chain; their roles are frequently linked to iron-sulfur cluster assembly and other essential biosynthetic processes. Hydrogenosomes, in contrast, generate ATP and hydrogen under anaerobic conditions mainly through substrate-level phosphorylation and may contain enzymes for pyruvate metabolism and ferredoxin-dependent reactions, but they usually lack a conventional respiratory chain.

Genetically, mitochondrial-like organelles frequently exhibit extreme genome reduction or altogether lack their own DNA, with most genes transferred to the host nucleus. This reduction reflects evolutionary adaptation to anaerobic lifestyles and reliance on cytosolic or host-derived metabolites. The concept of MROs helps unify diverse taxa that possess mitochondria-derived organelles with varying metabolic capabilities, highlighting the evolutionary plasticity of energy metabolism in eukaryotes.

Overall, mitochondrial-like organelles illustrate how endosymbiotic origins can diverge into a spectrum of organelles with specialized, often reduced, functions that support survival under specific environmental conditions.