ISSN:0149-0451    

DOI:10.1080/01490458909377845

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This paper describes important hydrologic features of the deep subsurface microbiology sampling sites. Geologic history, depositional environments, statigraphy, and groundwater movement are discussed in relation to possible mechanisms of microbial colonization of deep aquifer formations beneath the Savannah River Plant.

ISSN:0149-0451    

DOI:10.1080/01490458909377846

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The distribution of microorganisms in deep subsurface profiles was determined at three sites at the Savannah River Plant, Aiken, South Carolina. Acridine orange direct counts (AODC) of bacteria were highest in surface soil samples and declined to the 106to 107per gram range in the subsurface, but then did not decline further with depth. In the subsurface, AODC values varied from layer to layer, the highest being found in samples from sandy aquifer formations and the lowest in clayey interbed layers. Sandy aquifer sediments also contained the highest numbers of viable bacteria as determined by aerobic spread plate counts (CFU) on a dilute heterotrophic medium. In some of these samples bacterial CFU values approached 100% of the AODC values. Viable protozoa (amoebae and flagellates, but no ciliates) were found in samples with high bacterial CFU values. A variety of green algae, phytoflagellates, diatoms, and a few cyanobacteria were found at low population densities in samples from two of the three boreholes. Low numbers of fungi were evenly distributed throughout the profiles at all three sites. Microbial population density estimates correlated positively with sand content and pore‐water pH, and negatively with clay content and pore‐water metal concentration. A large diversity of prokaryotic and eukaryotic microorganisms was found in samples with high population densities. A survey of bacterial strains isolated from subsurface samples revealed associations of gram‐positive bacteria with high clay sediments and gram‐negative bacteria with sandy sediments. The ability to deposit lipophilic storage material (presumably poly‐ß‐hydroxybutyrate) was found in a high proportion of isolates from sandy sediments, but only rarely in isolates from high clay sediments.

ISSN:0149-0451    

DOI:10.1080/01490458909377847

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The aerobic, chemoheterotrophic bacteria indigenous to deep aquifers and other subsurface sediments (depths to 265 m) at a site in South Carolina were characterized by direct microscopy, enumeration of viable cells, analysis of colony morphologies on plates, and analysis of cell morphologies of isolated strains. Substantial numbers of viable bacteria (105‐108/g) were present in all transmissive, aquifer sediments, and their numbers did not decrease with depth. Fewer bacteria (<103/g) were detected in nontransmissive, confining layers. The highest viable counts were obtained on dilute media, but 10–50% of the bacteria in most aquifer sediments also grew rapidly on concentrated, nutrient‐rich media (indicating a high degree of metabolic flexibility). Most of the bacteria were mesophilic; relatively few psychrophiles or thermophiles were detected (<103/g; in many cases, none). The bacterial flora was diverse (11–62 distinct colony types on enumeration plates of most aquifer sediments). Diversity did not decrease with depth, but the composition of the microflora (based on colony analysis) varied extensively from one geological formation to another. Almost 95% of the platable colonies that grew on enumeration plates contained nonstreptomycete bacteria, more than 80% of which were gram‐negative rods. Light microscopy of films released from aquifer sediments by flotation revealed the presence of dividing cells and microcolonies, thus implying that the in situ deep aquifer microflora was more metabolically active than that seen previously in shallow aquifers.

ISSN:0149-0451    

DOI:10.1080/01490458909377848

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Subsurface sediments obtained from three cores drilled to depths of 260 m below the surface in South Carolina were analyzed for heterotrophic bacteria; N2‐fixing microaerophiles; and nitrifying, sulfur‐oxidizing, and H2‐oxidizing lithotrophic bacteria. In addition, pore waters were extracted for chemical analysis of inorganic nitrogen species, sulfate, dissolved organic carbon, pH, and Eh. Autotroph populations were generally less than 103most probable number (MPN) g‐1dry sediment with sulfur‐oxidizing bacteria, detected in 60% of the sediment samples, being the most frequently encountered group. Nitrifying bacteria were detected mainly in sediments from one borehole (P28), and their populations in those sediments were correlated with pore‐water ammonium concentrations. Populations of heterotrophic bacteria in 60% of the sediments were greater than 106colony forming units (CFU) g‐1dry sediment and were typically lower in sediments of high clay content and low pH. Microaerophilic N2‐fixing bacteria were cultured from >50% and bacteria capable of growth on H2were cultured from 35% of the subsurface sediments examined. Sediment texture, which controls porosity, water potential, and hydraulic conductivity, appears to be a major factor influencing microbial populations in coastal plain subsurface sediments.

ISSN:0149-0451    

DOI:10.1080/01490458909377849

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Subsurface sediment samples, collected from three boreholes ranging in depths from 0.1 to 260 m, were used in substrate mineralization studies to examine the aerobic metabolic potential of microbial populations indigenous to the deep subsurface. Mineralization was measured by quantifying the amount of14CO2released from radiolabeled acetate, phenol, or 4‐methoxybenzoate added to subsurface sediments at 10μg g‐1. Mineralization of the three compounds was observed in all but a few of the subsurface samples and did not decrease with depth. In addition, mineralization data collected from similar geologic formations from the different boreholes indicated that there was significant lateral continuity of microbial activity. Regression analyses were performed to determine which environmental factors were related to microbial metabolic potential. Mineralization was positively correlated with heterotrophic abundance as measured by plate counts. Other parameters that appeared to influence metabolic potential included pH and clay content.

ISSN:0149-0451    

DOI:10.1080/01490458909377850

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Activities of microorganisms residing in terrestrial deep subsurface sediments were examined in 46 sediment samples from three boreholes. Radiolabeled time course experiments assessing in situ microbial activities were initiated within 30 min of core recovery. [1‐C4] Acetate incorporation into lipids, [ methyl‐3H] thymidine incorporation into DNA, [2‐14C]acetate, and [U‐14C]glucose mineralization in addition to microbial enrichment and enumeration studies were examined in surface and subsurface sediments. Surface soils contained the greatest biomass and activities, followed by the shallow aquifer zones. Water‐saturated subsurface sands exhibited three to four orders of magnitude greater activity and culturable microorganisms than the dense clay zones, which had low permeability. Regardless of depth, sediments that contained more than 20% clays exhibited the lowest activities and culturable microorganisms.

ISSN:0149-0451    

DOI:10.1080/01490458909377851

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Methanogenesis, sulfate reduction, and rates of carbon mineralization were determined for samples derived at different depths from four cores drilled at the Savannah River Plant, Aiken South Carolina. Three‐gram subsamples of the sediments were dispensed to 10‐mL serum bottles under 5% H2/95% N2and amended with 0.5 mL degassed distilled water with or without the following solutes: formate plus acetate, bicarbonate, lactate, and radiolabeled sulfate, glucose, and Índole. After incubating 1 to 5 days, the sediments were assayed for methane, H2,35S, andI4CO2. No methanogenesis was detected at any depth in any core and sulfate was rarely reduced. Evolution of14CO2from glucose and indole was detected in sediments as deep as 262 and 259 m, respectively. At some depths the14CO2evolution rate was comparable to that of surface soils; however, at other depths no14CO2evolution could be detected. Injection of sterile air into anaerobic incubations increased rates of carbon mineralization at all depths that had demonstrated anaerobic activity and stimulated mineralization activity in sediments that were inactive anaerobically, suggesting a predominance of aerobic metabolism. Increasing the concentration of added glucose and indole often increased the resulting rates of14CO2evolved from these substrates. Our data indicate that both aerobic and anaerobic microorganisms are present and metabolically active in samples from deep subsurface environments.

ISSN:0149-0451    

DOI:10.1080/01490458909377852

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Dissimilatory nitrate reduction (denitrification) in subsurface sediments by indigenous microflora was investigated in samples obtained over a range of depths from 0 to 289 m. Denitrifying activity in sediment samples retrieved from similar stratigraphic horizons at four different sites was determined by measuring the accumulation of N2O using the acetylene blockage technique. Denitrification was detected in unamended samples which received only prereduced deionized water at almost all depths in all sediments sampled. The surface sediments showed the highest denitrification activity. In the deeper sediments, denitrifying activity was much higher in saturated sandy samples and lower or absent in drier clay samples. Addition of nitrate enhanced denitrification activity in all samples from below the water table down to the maximum depth sampled (289 m), while addition of a carbon (succinate) source in general had no stimulatory effect. These results show that denitrifying microorganisms were present in all of the deep subsurface sediments tested in this study. Furthermore, these results suggest that adequate supplies of metabolizable organic carbon were available to support denitrifying activity. However, denitrification may be limited by inadequate supplies of nitrate in the sediments.

ISSN:0149-0451    

DOI:10.1080/01490458909377853

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Anaerobic microorganisms were enumerated and metabolic activities measured in deep Coastal Plain sediments sampled from three water‐bearing formations at depths down to 300 m. Aseptically obtained sediment cores harbored the potential for anaerobic biodegradation of various substrates in almost all samples. Although the sediments were not predominantly anaerobic, viable methanogens and sulfate‐reducing bacteria (SRB) were present almost throughout the depth profile. Coliform organisms were also found at various locations, but were not recoverable from drilling muds or water used to slurry the muds. The anaerobic metabolism of lactate and formate was easily detected in most samples. However, acetate and benzoate were degraded only in portions of the subsurface that harbored methanogens. The water‐saturated transmissive zones harbored the highest numbers of SRB and the potential for the widest variety of anaerobic metabolic activities. Small or negligible anaerobic microbial activity was associated with thick clay layers. The accumulation of acetate and the production of methane in samples not amended with exogenous organic matter demonstrated that some strata contained reserves of fermentable carbon and suggested that environmental factors or nutrients other than carbon were potentially limiting in situ microbial activity.

ISSN:0149-0451    

DOI:10.1080/01490458909377854

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor