Abstract
Two bacterial isolates, designated S1.1 and S3.1, were recovered from oil-well produced water extracted from a deep and hot oil-well in the Thar Jath oil-field in South Sudan, and characterized. Based on their 16S rRNA gene sequences and phenotypic properties, the isolates were identified as members of the genus Thermoanaerobacter, possibly representing novel species. Both strains are strict anaerobes, grow optimally at 65 – 70°C at neutral pH and with ~0.3% NaCl, and can use various carbohydrates, proteinaceous compounds and organic acids as growth substrates. Strain S1.1 differs from strain S3.1 in its ability to grow on xylan and D-ribose, and S3.1 from S1.1 in its capacity to grow on acetate, arabinose, cellulose and lactate. Both produced acetate, ethanol, carbon dioxide and hydrogen as fermentation by-products from glucose, and growth was stimulated by thiosulphate. Strain S1.1 actively reduced Fe(III) as revealed by the formation of a dark paramagnetic precipitate and increased growth in cultures supplemented with Fe2O3. Cultures of both strains survived autoclaving at 121°C for 40 min, suggesting the formation of extremely heat-resistant endospores. Key words: Thermoanaerobacter, oil-well, produced water, deep biosphere, petroleum microbiology, thermophiles, Thar Jath.
Highlights
Deep Oil-field reservoirs represent extreme anaerobic environments with high temperature and pressure, toxic compounds, and limited nutrient availability
Strain S1.1 differs from strain S3.1 in its ability to grow on xylan and D-ribose, and S3.1 from S1.1 in its capacity to grow on acetate, arabinose, cellulose and lactate
Thermoanaerobacterium and gram-positive sulphatereducing Desulfotomaculum species from geographically widely separated high-temperature reservoirs, is taken as evidence for an indigenous microbial community in these habitats. This is supported by the fact that members of the genera Geotoga, Petrotoga and Thermovirga have only been obtained from oil-well produced waters (Dahle and Birkeland, 2006; Davey et al, 1993; Lien et al, 1998; Miranda-Tello et al, 2007; Miranda-Tello et al, 2004)
Summary
Deep Oil-field reservoirs represent extreme anaerobic environments with high temperature and pressure, toxic compounds, and limited nutrient availability. A number of anaerobic bacteria and archaeal isolates believed to be indigenous to these environments have been recovered and described, including fermentative organisms, methanogens, metal reducers, acetogens, and sulphate and nitrate reducers (Birkeland, 2004; Magot et al, 2000). Thermoanaerobacter and Thermoanaerobacterium and gram-positive sulphatereducing Desulfotomaculum species from geographically widely separated high-temperature reservoirs, is taken as evidence for an indigenous microbial community in these habitats. This is supported by the fact that members of the genera Geotoga, Petrotoga and Thermovirga have only been obtained from oil-well produced waters (Dahle and Birkeland, 2006; Davey et al., 1993; Lien et al, 1998; Miranda-Tello et al, 2007; Miranda-Tello et al, 2004). Subsurface microbial communities could represent a major part of the biosphere and
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