Effect of nitrate injection on the microbial community in an oil field as monitored by reverse sample genome probing

Abstract

The reverse sample genome probe (RSGP) method, developed for monitoring the microbial community in oil fields with a moderate subsurface temperature, has been improved by (i) isolation of a variety of heterotrophic bacteria and inclusion of their genomes on the oil field master filter and (ii) use of phosphorimaging technology for the rapid quantitation of hybridization signals. The new master filter contains the genomes of 30 sulfatereducing, 1 sulfide-oxidizing, and 16 heterotrophic bacteria. Most have been identified by partial 16S rRNA sequencing. Use of improved RSGP in monitoring the effect of nitrate injection in an oil field indicated that the sulfide-oxidizing, nitrate-reducing isolate CVO (a Campylobacter sp.) becomes the dominant community component immediately after injection. No significant enhancement of other community members, including the sulfate-reducing bacteria, was observed. The elevated level of CVO decayed at most sampling sites within 30 days after nitrate injection was terminated. Chemical analyses indicated a corresponding decrease and subsequent increase in sulfide concentrations. Thus, transient injection of a higher potential electron acceptor into an anaerobic subsurface system can have desirable effects (i.e., reduction of sulfide levels) without a permanent adverse influence on the resident microbial community. Oil fields at moderate subsurface depth and, consequently, with a moderate resident temperature harbor a complex microbial community that is being characterized in increasing detail (22, 27, 30). The metabolic potential of this community is characterized by an abundance of electron donors (aliphatic and aromatic hydrocarbons) but a shortage of electron acceptors (in order of increasing redox potential, carbon dioxide, sulfur and sulfate, ferric ions, nitrate, and oxygen). Stimulation and direction of the metabolism of this resident community are desirable for microbially enhanced oil recovery and to prevent the formation of excessive levels of sulfide (reservoir souring) by the action of sulfate-reducing bacteria (SRB), which has corrosive effects (7, 10). Both of these positive effects can be achieved by injection of nitrate, i.e., nitrate can serve as an alternate higher-potential electron acceptor (compared to sulfur or sulfate) and thus can stimulate the metabolic activity of the oil field microbial community. This can lead to increased oil recovery through microbial production of gas, emulsification of biopolymers, or the blockage of nonproductive subsurface channels (3). In addition, sulfide levels can be decreased through the action of bacteria that use sulfide as electron donor for nitrate reduction (12, 16, 26). However, some SRB are known to be able to use nitrate as well as sulfate as electron acceptors (18, 25, 32), and nitrate reduction coupled to sulfide oxidation may raise sulfate and sulfur levels. Thus, the increase in metabolic activity of the microbial population may be due in part to an unwanted increase in numbers and activity of SRB, for which reason i...

Bacterial freshwater species successfully immigrate to the brackish water environment in the northern Baltic

“…3, 4). Empirical estimates suggest that the level of cross-hybridization is ϳ2.5% for bacteria in general (Pinhassi et al 1997;Telang et al 1997), although it might be higher within a genus (16S rDNA similarity of 95-97%; Kisand et al 2002). As shown by Greene and Voordouw (2003), the influence of crosshybridization can vary, being less in limited diversity (e.g., enrichment cultures) than in very complex communities (ϳ1,000 species).…”

“…This method allows species-specific detection even at the low abundances typically found in natural environments, below the detection limit of direct microscopy (i.e., ϳ10,000 cells ml Ϫ1 ). Error rates from cross-hybridization have been shown to be low, suggesting DNA-DNA hybridization is sufficiently accurate to record bacteria at the species level (Pinhassi et al 1997;Telang et al 1997;Kisand et al 2002). DNA-DNA hybridization is easily applied and economical, thus allowing replication at various sampling levels, comparable to that applied in ecological studies of macroorganisms.…”

Nitrite reductase activity of sulphate‐reducing bacteria prevents their inhibition by nitrate‐reducing, sulphide‐oxidizing bacteria

“…Analysis of the microbial community composition indicated a strong increase in the nitrate-reducing, sulphide-oxidizing bacterium (NR-SOB) Thiomicrospira sp. strain CVO (Telang et al ., 1997;Gevertz et al ., 2000). In laboratory studies, it was shown that addition of Thiomicrospira sp.…”

Molecular characterization of a sulfate-reducing consortium which mineralizes benzene

“…Hydrothermal vents such as the one where the original inoculum for this culture was collected [25] are known to contain large numbers of the genus Thiomicrospira, and not all sul¢de oxidizers are strict aerobes [32]. In addition, investigations of the microbial community in anaerobic production waters at oil ¢elds have found signi¢cant numbers of sul¢de oxidizers [12,33].…”

“…Variations of these techniques have been used to study the microbial communities in hot springs [36], marine bacterioplankton [37], soils [38], marine sediments [39], oil ¢elds [12], activated sludge [40], and freshwater lakes [41]. The information gained by phylogenetically identifying the members of a consortium can be used to make inferences about the microbially mediated processes occurring in an environment [12,33] or to design isolation schemes for speci¢c bacteria [13].…”