Mitoilla

Mitoilla is a fictional term used in speculative biology and science fiction to denote a diminutive, mitochondrion-derived endosymbiont or organelle that could reside within the cytoplasm of a eukaryotic cell. The name blends mito- from mitochondrion with the diminutive suffix -illa, implying a smaller and more integrated form than a typical mitochondrion.

In educational and fictional models, mitoilla is described as a compact, double-membrane–bound structure with a greatly reduced genomic content. Its genome is imagined to be small, encoding only a limited set of essential components for energy metabolism, while most other functions are provided by the host cell or by host-encoded proteins imported into the organelle. Cristae, if present, may be simplified or irregular, and the organelle is typically depicted as housing a minimal set of ribosomes. Mitoilla would rely heavily on the host for metabolites and molecular machinery, rearranging its metabolic role toward specialized or localized energy production under specific cellular conditions.

Origin and significance in speculative scenarios focus on illustrating pathways of organelle evolution, such as reductive evolution or secondary endosymbiosis. Because mitoilla is not observed in real organisms, it remains a hypothetical construct used to explore questions about genome reduction, host–organelle integration, and the diversity of cellular energy strategies.

In practice, mitoilla appears in teaching discussions and fictional worldbuilding as a useful thought experiment about the evolution and function of intracellular organelles.