Cultivation-Based Characterization of Microbial Communities Associated with Deep Sedimentary Rocks from Taiwan Chelungpu Drilling Project Cores

Abstract

ABSTRACT1 Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC 2 Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC The Taiwan Chelungpu Drilling Project (TCDP) has provided an unprecedented opportunity to reveal a terrestrial subsurface microbial ecosystem that has possibly experienced continuous disturbance by the arccontinental collision since 5 Ma. The drilling penetrated Pliocene-Pleistocene sedimentary rocks to a depth of 2000 meters below the land surface (mbls) and encountered two major fault zones. Sixteen samples retrieved from the drilled cores at depths between 464 to 1451 mbls were examined to characterize microbial community structures through cultivation-based approaches. Cultivation experiments were performed with various media at temperatures ranging from 30 to 50°C. The results indicate that fermenters and heterotrophic sulfate reducers, using complex organic carbon, were ubiquitously present in most samples. Acetate-utilizing and H 2 -utilizing sulfate reducers were restricted to shallower intervals along the depth profile. Iron reducers and methanogens were only cultivated in a few shallow samples. Twelve pure strains including 8 fermenters, 3 iron reducers and Terr. Atmos. Ocean. Sci., Vol. 18, No. 2, June 2007 396 1 sulfate reducer originally enriched at 30 or 40°C were isolated and identified with 16S rDNA sequence analyses. They were phylogenetically affiliated with Firmicutes, Bacteriodes, Actinobacteria, and Proteobacteria in various degrees of similarity. The presence of metabolism was not correlated with lithology, depth, temperature and the appearance of fracture throughout the core. The ubiquitous appearance of fermentation and organotrophic sulfate reduction suggests that organic carbon sources were readily accessible in this deep terrestrial subsurface environment. These results infer that the foreland sedimentary strata disturbed by tectonic activities over a geological time scale might support a heterotrophy-dominated deep terrestrial subsurface microbial ecosystem.

Methanogenic Archaea Isolated from Taiwan's Chelungpu Fault

“…Coring was performed with a diamond-coated hollow bit with an inner diameter of 8.3 cm (57). Drilling fluid consisted of water pumped from an adjacent river, and bentonite and barite (BaSO4) were used to reduce heat, remove rock fragments generated during pulverization, and prevent groundwater intrusion.…”

“…Drilling fluid consisted of water pumped from an adjacent river, and bentonite and barite (BaSO4) were used to reduce heat, remove rock fragments generated during pulverization, and prevent groundwater intrusion. Rhodamine dye was added to the drilling fluid at a concentration of 50 ppm (wt/vol) to monitor contamination introduced during the coring (57). Each core section, with a maximum length of around 3 meters, was brought to the surface using a wireless core catcher.…”

“…Two major fracture zones were encountered: one was located within the Chinshui formation at around 1,110 mbls and the other at the boundary between the Kueichulin forma-tion and the underlying Cholan formation at around 1,750 mbls. At depths greater than 1,750 mbls, the Cholan formation was displaced underneath the Kueichulin formation by overthrusting along the deeper fracture zone (57).…”

“…Investigations of microbial communities have used 16S rRNA gene sequence analysis to characterize archaea in the deep subsurface such as in terrestrial rocks (45,52), petroleum reservoirs (8,9,18,39,40,42,58), faults (37,49,57), coal seams (11,48), gas fields (36), and subseafloor gas hydrates (17,33,35). These studies have demonstrated the abundance and diversity of methanoarchaea.…”

Workshop to develop deep-life continental scientific drilling projects

“…The geological context provides unique opportunities to address how microbial communities are shaped by and/or adapted to tectonic displacement of strata, pulse heat sterilization generated by fault shearing, and substrate availability and flux as-sociated with lithological transitions and active faulting. Previous analyses have revealed diverse and active microbial communities present at 1.5 km depth (Wang et al, 2007). At the workshop, the mud volcanoes in southwestern Taiwan were proposed as a potential ICDP-IODP drilling target as they extend along the same fault zone beneath the South China Sea.…”