MICROBIAL BIOPSHERE

Abstract

Evolution of the prokaryotic biosphere is regarded from the system point of view. It starts with the appearance of the first organisms, the ~3.5 Ga date forming the boundary between the observed and imagined biosphere. The prokaryotic community dominated from the Archean to the Mesoproterozoic. Prokaryotes make a sustainable community due to the cooperative action of specialized forms. The main route for establishing a community is made by trophic links. The structure of the trophic links in the prokaryotic community making a trophic network is an invariant, with secondary adaptive deviations. Material balance is the ultimate requirement for a long living self-supporting system. The system of biogeospheric cycles is dictated by the constancy of biomass composition establishing a quantitative ratio between Corg: Norg:Porg. Biospheric processes are driven by the Corg-cycle. Carbon assimilation is limited by the size of the illuminated moist surface populated by producers, meaning that Corg-production remains within an order of magnitude of 102 Gt/yr. Evolution of primary producers forms a basis for the evolution of the biospheric-geospheric system, and cyanobacteria integrated as chloroplasts remain its driving force. Decomposition of organic compounds is performed by organotrophic destructors, anacrobic being less effective. Destructors determine the residual Corg accumulation. Recalcitrant Corg remaining in the sedimentary record is equilibrated by O2 and other oxidized compounds as Fe-oxides or sulfates. Geospheric and biotic interactions include both direct and biotically mediated processes; the most important is the weathering-sedimentation pathway. Prokaryotic community makes a sustainable frame into which all other more complex forms of life fit. That makes the prokaryotic biosphere a permanent essence of the whole system. New participants might come in and substitute functional components only when they fit to the existing system. The evolution of a large system is additive rather than substitutive. The message of this is; "we all originated from the cyanobacterial community." © Pleiades Publishing, Inc. 2006.