ARCHAEOGLOBUS-FULGIDUS ISOLATED FROM HOT NORTH-SEA-OIL FIELD WATERS

A hyperthermophilic sulfate reducer, strain 7324, was isolated from ho t (75-degrees-C) oil field waters from an oil production platform in t he Norwegian sector of the North Sea. It was enriched on a complex med ium and isolated on lactate with sulfate. The cells were nonmotile, ir regular coccoid to disc shaped, and 0.3 to 1.0 mum wide. The temperatu re for growth was between 60 and 85-degrees-C with an optimum of 76-de grees-C. Lactate, pyruvate, and valerate plus H-2 were utilized as car bon and energy sources with sulfate as electron acceptor. Lactate was completely oxidized to CO2. The cells contained an active carbon monox ide dehydrogenase but no 2-oxoglutarate dehydrogenase activity, indica ting that lactate was oxidized to CO2 via the acetyl coenzyme A/carbon monoxide dehydrogenase pathway. The cells produced small amounts of m ethane simultaneously with sulfate reduction. F420) was detected in th e cells which showed a blue-green fluorescence at 420 nm. On the basis of morphological, physiological, and serological features, the isolat e was classified as an Archaeoglobus sp. Strain 7324 showed 100% DNA-D NA homology with A. fulgidus Z, indicating that it belongs to the spec ies A. fulgidus. Archaeoglobus sp. has been selectively enriched and i mmunomagnetically captured from oil field waters from three different platforms in the North Sea. Our results show that strain 7324 may grow in oil reservoirs at 70 to 85-degrees-C and contribute to hydrogen su lfide formation in this environment.