ИСТИНА

We attempted to reconstruct the “hatcheries” of the first cells by phylogenomic analysis of the inorganic ion requirements of cellular universal components that preceded the Last Universal Cellular Ancestor (LUCA). These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K+, Zn2+, Mn2+, and phosphate [1-3]. The high levels of these ions in modern cells is maintained by ion-tight cellular membranes and ion pumps. The very first organisms were unlikely to have such appliances, so that the inorganic chemistry of modern cytoplasm is believed to reflect the chemistry of the habitats of the first cells [3-6]. Specifically, building on the measured [K+]/[Na+] > 1.0 and high levels of Zn, Mn and phosphate in geothermal vapor condensate as sampled from vapor-dominated zones of inland geothermal systems, we have suggested that the first cells could have developed in primordial anoxic geothermal fields, where the elementary composition of the condensed vapor would resemble the internal milieu of modern cells [3]. Indeed, in the absence of oxygen, the transition metals would precipitate in such fields mostly as sulfides, whereby the slow precipitating and volatile Zn2+ ions [7] would selectively precipitate in far-off ponds and puddles, fed by cooled geothermal fluids and condensed vapor. We hypothesize that cool ponds, with their beds covered by clays and zeolites contaminated by sulfides and carbonates of Zn and Mn, may have served as the cradles for protocells. Anoxic geothermal fields, as putative cradles of life, would not only provided versatile catalysts for organic and inorganic molecules, but also support condensation reactions and enable the involvement of solar light as an energy source [3, 6, 8]. The predicted properties of anoxic geothermal fields have been recently confirmed by Van Kranendonk and colleagues who have described evaporative minerals containing precipitates of photoactive sphalerite (ZnS) and anatase (TiO2) from 3.48 Ga Dresser Formation, Pilbara Craton, Western Australia [9,10]. In the view of recent progress in understanding the geochemistry of the early Earth [11], the timing of the life origin would be discussed. Acknowledgements: The work was supported by the Federal Ministry of Education and Research of Germany, the Osnabrueck University (AYM) and the Russian Science Foundation (grant #14-50-00029). References 1. Mulkidjanian AY (2009) Biol Direct 4:26, 2. Mulkidjanian AY, Galperin MY (2009) Biol Direct 4:27. 3. Mulkidjanian, AY. et al. (2012) Proc Natl Acad Sci USA 109, E821-830. 4. Macallum, AB. (1926) Phys. Rev., 6:316-357. 5. Mulkidjanian AY, Galperin MY, Koonin EV (2009) Trends Biochem Sci 34:206–215. 6. Dibrova, DV et al. (2015) Biochemistry (Mosc) 80, 495-516. 7. Seewald JS, Seyfried WE (1990) Earth Planet Sci Lett 101:388–403. 8. Mulkidjanian, AY et al. (2003) BMC. Evol. Biol 3:12. 9. Djokic et al. (2017) Nature Comm. 15263. 10. Van Kranendonk et al. (2017) Life Springs, Sci. Amer. 317:28-35. 11. Albarede et al. (2015) Meteoritics & Planetary Science, 50: 568-577.