hide
Free keywords:
-
Abstract:
Scientific deep drilling in the Koyna seismogenic zone (Koyna, India), sheds new light into the prokaryotic denizens of the deep, dark, igneous crust hosted biosphere, spanning the basaltic formations of Cretaceous volcanism to the Archaean granitic horizon (59-2913 mbs) of the Deccan Traps. These enigmatic polyextremophilic oligotrophic microorganisms possess unique genetic traits that allow chemolithoautotrophic metabolism under conditions of high temperature, pressure and severe energy and nutrient limitations while driving biogeochemical cycles of carbon and other elements. Obligately anaerobic acetogenic and microaerophilic hydrogenotrophic bacteria were enriched from these rocks using specialised nutrient media under high temperature (50-70 ℃) and CO2 concentration (2-12% v/v). Their ability to assimilate hot CO2 gas and metabolize gaseous H2was investigated. 16S rRNA gene amplicon sequencing and predictive phenotyping have revealed the most abundant and metabolically productive genera to include Moorella, Bacillus, Anarobranca, Thermoacetogenia, Thermonaeromonas, Desulfofundulus, Desulfovibrio and Paracoccus. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2) analysis identified the most abundant autotrophic carbon fixation pathways to be reverse Krebs cycle, Calvin-Benson-Bassham cycle and Wood-Ljungdahl pathway; and major biosynthetic products as medium- and short-chain fatty acids, alcohols and antibiotics. Our research provides new insights into the geomicrobiological processes within the active seismogenic zone of Koyna and their possible correlation with various subsurface geophysical and geochemical properties. The study provides a better understanding of the overall system of such important geological provinces, highlighting the role of microorganisms and developing improved geomicrobiological methods to study such crystalline deep biosphere.
