entrometen

Entrometen are a fictional class of microorganisms described in speculative biology and science fiction narratives. They are not recognized by real-world biology, and there is no empirical evidence for their existence. In the imagined taxonomy used by these works, entrometen are ultra-small, single-celled organisms capable of rapid shape changes and occupying a middle ground between bacteria and eukaryotes. They are often depicted as lacking a rigid cell wall, with a flexible cytoskeleton and membrane-bound compartments that function as primitive organelles. Energy is typically derived from chemosynthesis, using minerals such as hydrogen sulfide or reduced iron from their surroundings.

In fiction, entrometen are described as inhabitants of dark, mineral-rich environments where light is scarce. Common settings include deep-sea hydrothermal vents, subglacial lakes, and porous subsurface aquifers. Their cellular architecture is portrayed as robust against high pressure and chemical variability, enabling survival in extreme conditions. Reproduction is usually asexual, by simple fission or budding, though some narratives allow limited horizontal transfer of genetic material within colonies.

Ecology and significance: Entrometen are often used as thought experiments to explore questions about minimal cellular organization, the evolution of metabolic pathways, and life's adaptability. They appear as plot devices in worldbuilding, helping to illustrate how life might arise and persist under conditions hostile to familiar organisms. They remain a fictional construct with no standing in established biology.