A SYSTEMATIC SURVEY FOR THERMOPHILIC FERMENTATIVE BACTERIA AND ARCHAEA IN HIGH-TEMPERATURE PETROLEUM RESERVOIRS

Production waters from 36 high temperature petroleum reservoirs were e xamined for the presence of thermophilic, fermentative microorganisms. The direct supplementation of production waters with glucose and eith er yeast extract, peptone, tryptone or casamino acid resulted in the i solation of thermophilic, fermentative microorganisms from 47% of the petroleum reservoirs examined. Three distinctive morphological groups were isolated from the production waters of petroleum reservoirs with depths ranging from 396-3048 metres, temperatures ranging from 21-130 degrees C, salinities ranging from 2.8-128 g1(-1) and pHs ranging from 6.0-8.5. Group 1 were pleomorphic rod-shaped bacteria, Group 2 were s heathed rod-shaped bacteria, and Group a were coccoid archaea. Partial characterisation of strains from one seawater-flooded petroleum reser voir and three non-waterflooded petroleum reservoirs tentatively ident ified some strains in Group 1 as members of the genera Thermoanaerobac ter and Thermoanaerobacterium, Group 2 as members of the Thermotogales order, and Group 3 as members of the genus Thermococcus. Production w ater salinity determined the type of microorganisms that were isolated . Group 1 organisms were found primarily in petroleum reservoirs with salinities less than 30 g/1, while Group 2 and 3 organisms were found to dominate in more saline reservoirs. The successful isolation of the rmophilic, fermentative microorganisms from petroleum reservoirs decre ased significantly with increasing salinity and temperature. These fin dings support the existence of a deep biosphere where fermentative mic rooganisms are widespread.