Diversity and activity of microorganisms in the Daqing oil field of China and their potential for biotechnological applications

Abstract

The numbers of microorganisms and the rates of sulfate reduction and methanogenesis were investigated in the formation water of the Daqing oil field, China. Physiological groups, aerobic saprotrophic and hydrocarbon-oxidizing, anaerobic fermentative, sulfate-reducing and methanogenic bacteria, were determined with MPN counts. Aerobic bacteria mostly inhabited the near-bottom zone of injection wells, where their number reached 10 3 -10 4 cells/mL. In formation water from oil-producing wells, the number of aerobic and anaerobic bacteria did not exceed 100 and 1000 cells/mL, respectively; the rate of sulfate reduction varied from 0 to 3.61 μg S 2- L -1 day -1 , and the rate of methanogenesis, from 0 to 7.28 μl CH 4 L -1 day -1 . More than 20 strains of aerobic bacteria were isolated from the Daqing oil field. The strains were identified based on their 16S rRNA gene nucleotide sequences. Many of the Gram-positive isolates fell into the genera Bacillus, Brevibacillus, Arthrobacter, Rhodococcus, Kocuria, Dietzia, Clavibacter, Cellulomonas, and Gordonia, Most of the Gram-negative isolates belonged to the genera Pseudomonas and Acinetobacter. The isolates were also characterized by their ability to produce exopolysaccharides and surfactants. High biotechnological potential of the formation microflora was revealed.