The continued exploration of Earth's biological potential has revealed a range of unexpected microbial habitats. The discovery of organisms inhabiting rokc interior, known as endoliths, was one such revelation that has altered our perspective of habitability, bioenergetics, and the relationship between biology and geology. Endolithic organisms were described during the early to mig 1900's, but their detailed study was initiated largely by E. Imre Friedmann, who published reports of rock-hosted algae in the Negev Desert and the Dry Valley of Anacrtica. In an attempt to standardize terminalogy, Golubic et al. (1981) formalized rock-associated subdivisions, providing three distinct catagories of endoliths (in contrast to exterior surface-associated organisms know as epiliths). The resulting description remains standard nomenclature to this day: "chasmoendolith" inhabit fissures and cracks, "cryptoendoliths" live in structural cavities, and "euendoliths" actively penetratre into rock interiors. Here, we propose a fourth subdivision: the "autoendoliths" (using the Greek prefix for 'self'), whose metabolism induces mineral precipitation, leading to the formation of a rocks that remains inhabited by the same kinde of organism. Three criterial demaracte the autoendolithic lifestyle as follows: 1. Microbial activity-dependent inducment of mineralization. This process may occur directly, whem metabolic products precipitate as mineral phases, or indirectly, when a microbial precipitate as mineral phases, or indirectly, when a microbial matrix such as extracellular polymeric substancnes (EPS) promotes and structures localized mineralization. 2. The formation of rock (as opposed to poorly lithified precipitates) as a result of extensive biological induced mineralization. 3. Continued metabolic activity within rock cavities.
The continued exploration of Earth's biological potential has revealed a range of unexpected microbial habitats. The discovery of organisms inhabiting rokc interior, known as endoliths, was one such revelation that has altered our perspective of habitability, bioenergetics, and the relationship between biology and geology. Endolithic organisms were described during the early to mig 1900's, but their detailed study was initiated largely by E. Imre Friedmann, who published reports of rock-hosted algae in the Negev Desert and the Dry Valley of Anacrtica. In an attempt to standardize terminalogy, Golubic et al. (1981) formalized rock-associated subdivisions, providing three distinct catagories of endoliths (in contrast to exterior surface-associated organisms know as epiliths). The resulting description remains standard nomenclature to this day: "chasmoendolith" inhabit fissures and cracks, "cryptoendoliths" live in structural cavities, and "euendoliths" actively penetratre into rock interiors. Here, we propose a fourth subdivision: the "autoendoliths" (using the Greek prefix for 'self'), whose metabolism induces mineral precipitation, leading to the formation of a rocks that remains inhabited by the same kinde of organism. Three criterial demaracte the autoendolithic lifestyle as follows: 1. Microbial activity-dependent inducment of mineralization. This process may occur directly, whem metabolic products precipitate as mineral phases, or indirectly, when a microbial precipitate as mineral phases, or indirectly, when a microbial matrix such as extracellular polymeric substancnes (EPS) promotes and structures localized mineralization. 2. The formation of rock (as opposed to poorly lithified precipitates) as a result of extensive biological induced mineralization. 3. Continued metabolic activity within rock cavities.