Microbial control of the production of hydrogen sulfide by sulfate-reducing bacteria.

A sulfide-resistant ctrain of Thiobacillus denitrificans, strain F, prevented the accumulation of sulfide by Desulfovibrio desulfuricans when both organisms were grown in liquid medium or in Berea sandstone cores. The wild-type strain of T. denitrificans did not prevent the accumulation of sulfide produced by D. desulfuricans. Strain F also prevented the accumulation of sulfide by a mixed population of sulfate-reducing bacteria enriched from an oil field brine. Fermentation balances showed that strain F stoichiometrically oxidized the sulfide produced by D. desulfuricans and the oil field brine enrichment to sulfate. These data suggest that strain F would be effective in controlling sulfide production in oil reservoirs and other environments.

Method for detection of microorganisms that produce gaseous nitrogen oxides.

A method was developed to detect NO- or N(2)O-producing bacteria in solid or liquid medium by their ability to oxidize the redox indicator resazurin from its reduced colorless form to its oxidized pink form. The method was sensitive to as little as 35 nM N(2)O or 0.5 nM NO. Ninety-one percent of the colonies that oxidized resazurin on plates also produced N(2)O in slant cultures. Forty-four percent of the colonies that did not oxidize resazurin did produce N(2)O. This percentage was reduced to 15% when colonies in which the coloration was difficult to discern were picked to slants to determine whether they oxidized the slant. The production of N(2)O preceded the oxidation of resazurin by liquid cultures of Escherichia coli and a sludge isolate. With the denitrifying sewage isolate, the disappearance of N(2)O was followed by the return of resazurin to its reduced state. Wolinella succinogenes was found to produce small amounts of N(2)O from NO(3), which resulted in a transient oxidation of resazurin.