hostol

Hostol is a term used in speculative biology to denote a hypothesized cellular organelle or vesicular structure involved in host–molecule exchange in some eukaryotic microorganisms and primitive metazoan cells. It is described as a discrete, membrane-enclosed compartment that participates in the transfer of materials between a host cell and its intracellular or extracellular milieu.

Etymology and scope

The name combines the root host with a suffix used for organ-like structures. The concept arose in early 2010s speculative literature as a potential mechanism for modular nutrient and signal exchange between host organisms and associated symbionts or endosymbionts. It remains disputed and is not part of established cell biology.

Structure and proposed function

Reported descriptions place hostols at roughly 0.1–0.5 micrometers in diameter, bounded by a single limiting membrane and containing electron-dense cores or granules. The proposed function is to mediate selective import and trafficking of macromolecules—proteins, lipids, and nucleic acids—between the host cytoplasm and the surrounding environment or symbiotic partners. In some accounts, hostols are thought to coordinate signaling and nutrient exchange, supporting symbiotic maintenance.

Occurrence and assessment

Evidence for hostols comes from a small number of exploratory studies and remains controversial. Critics emphasize methodological limitations and the lack of reproducible markers. As such, hostol is viewed as a hypothetical construct in need of robust, independent verification before it can be considered a validated cellular component.

See also

Endocytosis, Organelle, Symbiosis, Cryo-electron microscopy.