Boreskov

OP‐17HABITALS AND ENERGETICS OF FIRST CELLSMulkidjanian A.Y.School of Physics, University of Osnabrück, 49076, Osnabrück, Germany, andA.N. Belozersky Institute of Physico‐Chemical Biology, Moscow State University,Moscow, 119991, Russia, e‐mail: amulkid@uos.deLife can exist only when supported by energy flow(s). Here, it is argued that theevolutionarily relevant, continuous fluxes of reducing equivalents, which were needed forthe syntheses of first biomolecules, may have been provided by the inorganicphotosynthesis and by the redox reactions within hot, iron‐containing rocks. The onlyprimordial environments where these fluxes could meet were the continental geothermalsystems. The ejections from the hot, continental springs could contain, on the one hand,hydrogen and carbonaceous compounds and, on other hand, transition metals, such as Znand Mn, which precipitated around the springs as photosynthetically active ZnS and MnSparticles capable of reducing carbon dioxide to diverse organic compounds. At high pressureof the primordial CO 2 atmosphere, both the inorganic photosynthesis and the abioticreduction of carbon dioxide within hot rocks should have proceeded with high yield. Amonga plethora of abiotically produced carbonaceous molecules, the natural nucleotides couldaccumulate as the most photostable structures; their polymerization and folding intodouble‐stranded segments should have been favored by the further increase in thephotostability. It is hypothesized that after some aggregates of photoselected RNA‐likepolymers could attain the ability for self‐replication, the consortia of such replicating entitiesmay have dwelled within porous, ZnS‐contaminated silicate minerals, which provided shelterand nourishment. The energetics of the first cells could be driven by their ability to cleavethe abiogenically formed organic molecules and by reactions of the phosphate grouptransfer. The next stage of evolution may be envisaged as a selection for increasingly tighterenvelopes of the first organisms; this selection may have eventually yielded ion‐tight lipidmembranes able to support the sodium‐dependent membrane bioenergetics. Lastly, theproton‐tight, elaborate membranes independently emerged in Bacteria and Archaea andenabled the transition to the modern‐type proton‐dependent bioenergetics.References[1]. Mulkidjanian, A. Y., Cherepanov, D. A., and Galperin, M. Y. (2003), 'Survival of the fittest before thebeginning of life: selection of the first oligonucleotide‐like polymers by UV light', BMC Evol Biol, 3, 12.58