Cultivation Of Alkaliphlic Iron-Reducing Bacteria In Ultra-pressure Metamorphic Rocks Collected From Chinese Continental Scientific Drilling Program (CCSD)

A novel iron-reducing alkaliphilic anaerobic species was isolated from an 880-m-depth drilling mud sample of a subsurface borehole of CCSD (Chinese Continental Scientific Drilling Program). The bacterium displayed a slightly curved rod morphologically, and was physiologically characterized with an optimal temperature of 38℃, the salinity of (NaCl), (KCl), respectively, and an optimal pH 9.4. The strictly anaerobic bacterium was able to utilize various carbon substrates such as peptone, nutrient broth, lactate, cellobiose, glucose, ribose, fumarate and so on. The G+ C content of genomic DNA was 35.4 mol%. Phylogenetic analysis based on the 16S rRNA sequence indicated that the isolate is a member of Firmicutes within the low G+C Gram-positive bacteria. Phylogenetic analysis of the 16S rRNA indicated the bacterium was a low G+C Gram-positive microorganism in the Clostridiaceae, and had 94% and 93% nucleotide identity with Anaerobranca gottschalkii and Anaerobranca californiensis, respectively. The isolate represented a novel metal-reducing, alkaliphilic species and the name Alkaliphilus Aanaerobium sp. nov. is proposed based on its physiological and molecular properties. The highly anaerobic habitat and the comparison with other isolates from the CCSD boreholes are discussed. The interactions between the iron-reducing and iron-bearing minerals are also tested in the paper.