HR: 0800h
AN: B41C-0212    [Abstracts]
TI: Unique Microbial Community in Drilling Fluids from Chinese Continental Scientific Drilling
AU: * Zhang, G
EM: zhangg@muohio.edu
AF: Department of Geology, Miami University, oxford, OH 45056
AU: Dong, H
EM: dongh@muohio.edu
AF: Department of Geology, Miami University, oxford, OH 45056
AU: Jiang, H
EM: jiangh@muohio.edu
AF: Department of Geology, Miami University, oxford, OH 45056
AU: Xu, Z
B41C-0212 AF: Key Laboratory for Continental Dynamics, Chinese Academy of Geological Sciences ,Institute of Geology, , Beijing, 100037 China
AB: Circulating drilling fluid is often regarded as a contamination source in investigations of subsurface microbiology. However, it also provides an opportunity to sample geological fluids at depth and to study contained microbial communities. During our study of deep subsurface microbiology of Chinese Continental Scientific Deep drilling project, we collected 6 drilling fluid samples from a borehole from 2290 to 5100 m below the ground surface. Microbial communities in these samples were characterized with cultivation-dependent and -independent techniques. Characterization of 16S rRNA genes indicated that the bacterial clone sequences related to Firmicutes became progressively dominant with increased depth. Most sequences were related to anaerobic, thermophilic, halophilic or alkaliphilic bacteria. These habitats were consistent with the measured geochemical characteristics of the drilling fluids that have incorporated geological fluids and partly reflected the in-situ conditions. Several clone types were closely related to Thermoanaerobacter ethanolicus, Caldicellulosiruptor lactoaceticus, and Anaerobranca gottschalkii, an anaerobic metal-reducer, an extreme thermophile, and an anaerobic chemoorganotroph, respectively. Their optimal growth temperature was between 50-85­aC. Anaerobic, thermophilic Fe(III) reducing bacterial isolates were obtained and they were capable of reducing Fe(III) in iron oxide and clay mineral to produce siderite and vivianite, and illite, respectively. Anaerobic, thermophilic Fe(II) oxidizing bacterial isolate was able to oxidize Fe(II) in clay structure. Biological iron redox cycles may be present in the deep subsurface. The archaeal diversity was low. Most archaeal sequences were not related to known cultivated species, but to environmental clone sequences recovered from subsurface marine environments. We infer that the detected microbes were derived from geological fluids at depth and their growth habitats reflected the deep subsurface environments. These findings have important implications for microbial ecology in the deep subsurface . Analyzing drilling fluid might provide us with a new method to study subsurface microbiology.
DE: 0410 Biodiversity
SC: Biogeosciences [B]
MN: Fall Meeting 2005