| Popis: |
This study reports deep biosphere related outcomes of the scientific drilling into the seismogenic zones of Koyna (India) and South African gold mine and presents a comparative account of microbial ecology across the continental settings (by including geomicrobiological data from Fennoscandian and SAFOD deep drilling / biosphere sites as well). ICDP DSeis project (SA) and Ministry of Earth Sciences (India) - ICDP Koyna scientific drilling allowed us to drill and recover Archean granitic rock cores from deep Earth crust (~3-4 km) and investigate the patterns of deep biosphere microbial ecosystems. Deep crystalline rock hosted microbial communities are elucidated by sequencing the 16S rRNA genes from extracted total DNA of the rock samples. Two rock core samples obtained from borehole B (~3330 meter below surface; representing quartzite from the Babrasco Formation) drilled at the Moab Khotsong Gold mine and several rock samples obtained from various depths of Koyna exploratory and pilot boreholes are used. Microbial taxa affiliated to Burkholderiace dominated (>30% relative abundance) the SA deep rocks. Predominance of multiple hydrogen metabolizing genera such as Comamonas, Ralstonia, Burkholderia-Caballeronia-Paraburkholderia, Enhydrobacter, extremotolerant Corynebacterium and C1- compound metabolizing Methylobacterium could be noted. In contrast, the deep biosphere of Koyna (down to 2910 meter below surface) is found to be constituted by multiple taxa with relatively lower abundance. Abundance of extremotolerant Actinobacteria (Micrococcaceae and Corynebacteriace), Pseudomonadaceae, Burkholderiaceae and Opitutaceae is noted. WPGMA based clustering suggests that microbial communities of Deccan trap subsurface are significantly different from its South African counterparts; and the latter are somewhat similar to microbial communities previously reported from Fennoscandian deep biosphere. Presence of several unique taxa is identified in each of these habitats. Members of Thermoactinomycetaceae, Planococcaceae, Babeliaceae, Thermomonosporaceae and several Clostridial families are found as unique taxa in SA deep biosphere, while Thermoanerobaculaceae, Cyclobacteriaceae, Acidothermaceae, Thioalkalispiraceae, etc. represented those of the deep biosphere underneath the Deccan. The study highlights the pattern of deep granitic crust hosted microbial communities and reinforces the need to develop and adopt more universal sampling and experimental approaches in deep life research. |
