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In natural ecosystems, bacteria, unicellular algae, filamentous and yeast-like fungi are often organised in thin films attached to or entrenched in substrata such as surfaces of solid rocks, minerals or larger organisms. Frequently the formation of a biofilm is the most successful survival strategy. Especially within endolithic biofilms micro-organisms actively create a safe niche to avoid extreme and thus harmful environmental conditions such as electromagnetic radiation, mechanical abrasion, water and temperature stress and hazardous chemical agents. Exemplary survival strategies are presented for bacteria, ascomycetes and green algae. On substrata without organic carbon sources, biofilms are composed of chemolithotrophic or phototrophic primary producers and heterotrophic organisms (including destruents).

Pioneer colonization by endolithic biofilms have been studied on barren, seemingly uninhabitable carbonate rock surfaces in Alpine regions. The geochemical effects of endolithic biofilms on rock surfaces have been studied using a range of microanalytical methods. The metabolism of the biofilms produces a specific pattern of relative element enrichment or depletion (geochemical fingerprint).