Lithophiles aremicro-organisms that can live within the pore interstices ofsedimentary and evenfracturedigneous rocks to depths of several kilometers.

Some are known to live on surface rocks, and make use ofphotosynthesis for energy.

Those that live in deeper rocks cannot usephotosynthesis to gather energy, but instead extract energy from minerals around them. They live in cracks in the rock where water seeps down. The water contains dissolvedcarbon dioxide (CO₂) which the organisms use for their carbon needs.^[1] They have been detected in rocks down to depths of nearly three km, where the temperature is approximately 75 °C.

Terrestrial lithophiles can be found in canyons primarily composed ofgranite, an igneous rock, and soils saturated with fractured rock.^[2] Organisms from the genusElliptochloris, a subaerial photosynthetic green algae,^[3] demonstrate lithophilic preferences through colonization in granite cracks and in proximity to terrestriallichens.^[2] Lithophilic lichens from the genusCollema form tight symbiotic relationships between fungi and photosynthetic algae such asElliptochloris in order to produce necessary saturated fatty acid secondary metabolites.^[4] Lithophilic algal species colonizing fractured rock outcroppings individually exhibitcoccal morphological shape while aggregating into an elliptical or globular arrangement during adulthood.^[5]

Lithobiontic ecological niches further classify lithophiles into sub-categories determined by their spatial niche specificity. The term, lithic, refers to an association with rock and can be further explained by the term, lithobiontic, regarded as organisms living both on, and within rock surfaces.^[6] Sub-surface rock organisms, endoliths, primarily exhibit niche preference within fissures, cavities, or tunnels of various rocks. While many endoliths degrade and effectively excavate the availablecarbonate rock surface, many are preyed upon by selectgastropod, andechinoderm species. This habitat preference can be further threatened by suspension feeding organisms searching for acquired shelter.^[6]