Identification and Phylogenetic Analysis of Thermophilic Sulfate-Reducing Bacteria in Oil Field Samples by 16S rDNA Gene Cloning and Sequencing

Abstract

Thermophilic sulfate-reducing bacteria (SRB) have been recognized as an important source of hydrogen sulfide (H2S) in hydrocarbon reservoirs and in production systems. Four thermophilic SRB enrichment cultures from three different oil field samples (sandstone core, drilling mud, and production water) were investigated using 16S rDNA sequence comparative analysis. In total, 15 different clones were identified. We found spore-forming, low G+C content, thermophilic, sulfate-reducingDesulfotomaculum-related sequences present in all oil field samples, and additionally a clone originating from sandstone core which was assigned to the mesophilicDesulfomicrobiumgroup. Furthermore, three clones related to Gram-positive, non-sulfate-reducingThermoanaerobacterspecies and four clones close toClostridium thermocopriaewere found in enrichment cultures from sandstone core and from production water, respectively. In addition, the deeply rooted lineage of two of the clones suggested previously undescribed, Gram-positive, low G+C content, thermophilic, obligately anaerobic bacteria present in production water. Such thermophilic, non-sulfate-reducing microorganisms may play an important ecological role alongside SRB in oil field environments.