OCCURRENCE OF SULFATE-REDUCING AND IRON-REDUCING BACTERIA IN STRATAL WATERS OF THE ROMASHKINSKOE OIL-FIELD

The occurrence of microorganisms and the rates of terminal biogenic pr ocesses - sulfate reduction and methane synthesis - were studied in st ratal waters in bed 302 of the Bashkir Carboniferous deposit at the Ro mashkinskoe oil field. It was shown that bed 302 was a dynamic, highly reduced ecosystem containing sulfates and hydrogen sulfide in conside rable concentrations, in which active biogenic processes occurred. Sul fate reduction was a dominating anaerobic process by which the transfo rmation of organic matter occurred. The sulfate-reducing microflora wa s diverse and characterized by a wide range of metabolic potentials. E nrichment cultures capable of oxidizing many organic substances, such as benzoate, acetate, ethanol, or lactate, at the expense of reduction of sulfates and ferric ion were isolated from bed 302. It was suggest ed that the sulfate-reducing microflora might be responsible not only for sulfate reduction in the stratum but also for mobilization of some insoluble iron oxides in the oil-bearing rock. These findings indicat e that bacteria carrying out dissimilatory reduction of sulfate and ir on can contribute to the geochemistry of organic and mineral compounds in subsurface ecosystems.