ISSN:0149-0451    

DOI:10.1080/01490459809378081

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this review, we summarize the important recent findings relating to arsenate respi‐ration by bacteria. A brief discussion of freshwater arsenic cycling is provided, with attention placed on the microbial contributions to this cycle. The basic evidence for microbial growth on arsenate is presented for studies with both consortia and isolates, followed by a summary of the physiology and phytogeny of four arsenate‐respiring bac‐teria:Chrysiogenes arsenatisstrain BAL‐1T, Desulfotomaculum auripigmentumstrain OREX‐4, Sulfurospirillum arsenophilusstrain MIT‐13, andS. barnesiistrain SES‐3. Drawing on biochemical studies of the arsenate reductasefromS. barnesiistrain SES‐3, a preliminary model for growth on arsenate is proposed. We conclude with a discussion of the importance of microbial arsenate reduction in the environment.

ISSN:0149-0451    

DOI:10.1080/01490459809378082

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The role of Fe(II) biosorption and the effect of medium components on the rate and long‐term extent of Fe(III) oxide reduction (FeRed) by a dissimilatory Fe(III)‐reducing bacterium(Shewanella algastrain BrY) were examined in batch culture experiments. Introduction of freshS. algacells into month‐old cultures in which Fe(III) reduction had ceased resulted in further reduction of synthetic amorphous Fe(III) oxide, hematite, and two forms of goethite (Gt). FreshS. algacells were also able to reduce a substantial amount of synthetic Gt that had been partly or completely saturated with sorbed Fe(II). Cells that had been precoated with Fe(II) showed a reduced rate and capacity for FeRed. These results indicated that biosorption of Fe(II) had a major impact on FeRed.S. algacells were shown to have an Fe(II) sorption capacity of ∼0.1 mmol g−1, compared with ∼0.25 mmol g−1determined for the synthetic Gt. Sorption experiments with component mixtures indicated that direct interaction between cells and oxide resulted in increased Fe(II)‐binding capacity of the mixed system, possibly through production of exopoly‐meric materials by the cells. Medium constituents that affected Fe(II) speciation were shown to have a significant indirect influence on the extent of oxide reduction. Malaie, which formed soluble complexes with Fe(II), promoted the extent of oxide reduction. In contrast, high (mM) PO43−concentrations favored surface/bulk precipitation processes which reduced the extent of oxide reduction. Collectively, our results indicate that Fe(II) sorption by oxide and cell surfaces, together with Fe(II) complexation by or precipita‐tion with medium components, all influence the rate and extent of FeRed. Furthermore, saturation of sorption sites with Fe(II) does not appear to limit the ability ofS. algato reduce Fe(III) oxides, especially if conditions favor growth.

ISSN:0149-0451    

DOI:10.1080/01490459809378083

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

As a first step towards understanding microbial dissolution processes, our research focuses on characterizing attachment features that form between aPseudomonassp. bacteria and the Fe(III)‐(hydr)oxide minerals hematite and goethite. Microbial growth curves in Fe‐limited growth media indicated that the bacteria were able to obtain Fe from the Fe(III)‐(hydr)oxidesfor use in metabolic processes. A combination of scanning electron microscopy, epifluorescence, and Tapping Mode™ atomic‐force microscopy showed that the bacteria colonized some fraction of mineralogical aggregates. These aggregates were covered by bacteria and were linked together by relatively open biofilms consisting of networks of fiber‐like attachment features intertwined through thin films of amorphous‐looking organic material. The biofilm material encompassed numerous individual bacteria, as well as minéralogie particles. We hypothesize that the bacteria first attached to mineral aggregates, perhaps via their flagella, forming colonies. Following initial attachment, the bacteria exuded additional attachment features in the form of fine, branching fibrils intertwined through thin films. The detailed structures of these attachment features were highlighted by Phase Imaging atomic‐force microscopy, which served as a real‐time contrast enhancement technique and showed some poorly defined sensitivity to different surface materials, most probably related to differences in stiffness or viscoelasticity. Although the mechanism of the microbially enhanced dissolution remains unknown, we hypothesize that the bacteria may have produced micro environments conducive to dissolution through the use of observed extracellular materials.

ISSN:0149-0451    

DOI:10.1080/01490459809378084

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The present study documents the precipitation of Fe(III), silica, and sulfate in the presence of 3 different bacteria(Bacillus subtilus, Bacillus licheniformis, andPseudomonas aeruginosa), under different total Fe(III) concentrations (10−2M, 10−3M, 10−4M) at constant pH (4.0). Morphology and chemical composition of the precipitates were compared with those formed in abiotic control systems, while chemical composition and precipitation of the precipitates were modeled according to solution chemistry data. Transmission electron microscopy (TEM) observations showed morphological differences between the biotic and abiotic systems. All systems contained small grains (diam. 2–50 nm), but amorphous material (i.e., material without any specific morphology) and nodules were present only in the cell systems. This is because bacterial surfaces and exopolymers provided numerous binding sites for metal and anion sorption and promoted heterogeneous nucleation of hydrous ferric oxides (HFO). The initial Fe/Si and Fe/SO4molar ratios of the solutions dictated the type of precipitates in most systems, since abiotic control systems were saturated to oversaturated with respect to amorphous silica, siliceous ferrihydrite, schwertmannite, ferrihydrite, goethite, or combinations of these. Of the three strains studied,B. licheniformisappeared to have the greatest influence on the chemical composition of the precipitates, especially in the presence of Si.B. licheniformis(a gram‐positive bacterium with a large capsule) favored the precipitation of HFO containing less Si than the predicted solids, because Si rather than Fe oxides was preferentially sorted to extracellular polymers (capsule). On the other hand, the formation of SO4‐rich HFO (similar to schwertmannite) did not seem to be affected by the presence of bacteria.

ISSN:0149-0451    

DOI:10.1080/01490459809378085

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Rates of organic matter mineralization in peatlands, and hence production of the greenhouse gases CH4and CO2, are highly dependent on the distribution of oxygen in the peat. Using laboratory incubations of peat, we investigated the sensitivity of the anoxic production of CH4and CO2to a transient oxic period of a few weeks’ duration. Production rates during 3 successive anoxic periods were compared with rates in samples incubated in the presence of oxygen during the second period. In surface peat (5–10‐cm depth), with an initially high level of CH4production, oxic conditions during period 2 did not result in a lower potential CH4production rate during period 3, although production was delayed ∼1 week. In permanently anoxic, deep peat (50–55‐cm depth) with a comparatively low initial production of CH4, oxic conditions during period 2 resulted in zero production of CH4during period 3. Thus, the methanogens in surface peal—but not in deep peat—remained viable after several weeks of oxic conditions. In contrast to CH4production, the oxic period had a negligible effect on anoxic CO2production during period 3, in surface as well as deep peat. In both surface and deep peat, CO2production was several times higher under oxic than under anoxic conditions. However, for the first 2 weeks of oxic conditions, CO2production in the deep peat was very low. Still, deep peat obviously contained facultative microorganisms that, after a relatively short period, were able to maintain a considerably higher rate of organic matter mineralization under oxic than under anoxic conditions.

ISSN:0149-0451    

DOI:10.1080/01490459809378086

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Production of biomass by indigenous bacteria found in hypersaline oil‐reservoir brine was limited by a fermentable carbon and phosphorus source. The addition of polymeric carbohydrates, such as maltodextrins, along with organic phosphates stimulated production of a flocculent and sometimes slimy biomass, which was not produced from simple sugars. Maltodextrins also stimulated production of lower levels of the end‐products acetate and ethanol. Injection of indigenous bacteria into sandstone cores followed by phosphate and maltodextrin resulted in a >90% reduction in the in‐depth permeability of a sandstone core, whereas treatment with glucose resulted in primarily face‐plugging of a sandstone core. These corns tarch maltodextrins and organic phosphate esters have application as nutrients for stimulation of biomass necessary for selective plugging of reservoir rock by microbial populations found in a hypersaline oil reservoir.

ISSN:0149-0451    

DOI:10.1080/01490459809378087

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To understand the conditions under which microorganisms exist in deep hydrocarbon reservoirs, sidewall cores were collected from a natural gas‐bearing formation, 2800 m below the surface in Taylorsville Basin, Virginia. Data from chemical and microbial tracers and controls indicate that the interiors of some sidewall cores contained microorganisms indigenous to the rock formation. The cultured microorganisms were composed primarily of saline‐tolerant, thermophilic fermenting, Fe(III)‐reducing, and sulfate‐reducing bacteria (1 to 104cells/g). The physiological capabilities of the cultured microorganisms are compatible with the temperature (76°C), pressure (32 MPa), and salinity (≈0.8 wt.% NaCl equivalent) in the sampled interval. The petrological data indicated that the strata contain intercrystalline pores of micrometer size, that occur between late diagenetic cement in siltstone and within cross‐cutting, mineralized fractures in shale. These pores made up only 0.04% of the rock volume, were mostly gas‐filled, and were interconnected by pore throats with diameters <0.04 μm. Because the pore throats are smaller than known bacteria, the cultured microorganisms were probably trapped within the larger pores containing alkaline, brackish, formation water. The total phospholipid fatty acid concentration of the rock samples yielded a cellular concentration equivalent to 4 x 105cells/g, much greater than had been determined by enumeration of the cultured bacteria. This may have resulted from either inhibition of dephosphorolation reactions within pores filled with reduced gases, such as methane, or the inability to culture >0.1% of the viable bacteria. The recovery of living bacteria from such an austere environment represents one of the most remarkable examples of microbial survival yet reported.

ISSN:0149-0451    

DOI:10.1080/01490459809378088

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459809378089

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490459809378080

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor