摘要:

Previous research has indicated that halophilic microorganisms are associated with salt crystals from ancient formations. However,this research has generally failed to convincingly demonstrate that these organisms were originally trapped inside the crystals during their deposition and were not recent surface contaminants. This paper presents techniques for crystal selection; verifiable, noninvasive, surface sterilization of salt crystals; and sterile extraction of biological material from the crystals. Immersing salt crystals in 10 M NaOH for 5 min; rinsing with sterile, saturated brine before immersing for 5 min in 10 M HCl; and rinsing with saturated brine is an effective method for surface sterilization. No growth has resulted from contamination tests of 216 faces from 36 natural salt crystals exposed to these treatments. Pure culture experiments using the halotolerant eubacteria, Halomonas elongata and Bacillus sp. (2-9-3), and the archeon, Halogeometricium borinquense, showed that exposure to either 10 M HCl or NaOH reduced the population of these organisms by a factor of 107to 108colony-forming units/ml. The fluid is extracted from inclusions by drilling into surface-sterilized salt crystals with a variable-speed drill using sterilized 0.5-mm-diameter carbide drill bits and extracting the fluid with a sterilized microliter syringe. Drilling and extraction are performed in a Class II biosafety cabinet. All procedures are carried out in a biosafety level 3 facility. All personnel involved wear cleanroom coveralls, shoe covers, hair caps, and gloves. The above protocol has resulted in the isolation of a Bacillus sp. from a Permian-age salt crystal.

ISSN:0149-0451    

DOI:10.1080/01490450050121152

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The acidophilic heterotrophic eubacterium Acidiphilium SJH was shown to catalyze the reductive dissolution of a wide range of ferric iron?containing minerals (akageneite, goethite, jarosite, natrojarosite, and amorphous ferric hydroxide) and of the mixed ferrous/ferric mineral magnetite. The specific rates of dissolution varied with the structural stabilities of the minerals, such that amorphous ferric hydroxide was the most rapid and jarosite and akageneite were the slowest of the minerals tested. The reductive dissolution of both amorphous ferric hydroxide and magnetite was faster in pH 2.0 than in higher pH (2.8?3.0) cultures, even though Acidiphilium SJH has a pH optimum close to pH 3. Contact between bacteria and ferric mineral was not necessary for reductive dissolution to occur. Adding EDTA or diethylenetriamine pentaacetic acid to bacterial cultures accelerated the solubilization of goethite and amorphous ferric hydroxide. Although cell-free spent media and heat-killed Acidiphilium SJH also appeared to enhance mineral dissolution (indicated by formation of soluble Fe3 + ), this was far less extensive than that in active bacterial cultures, and no iron reduction was observed in the absence of viable cells. Experimental results suggested that Acidiphilium SJH accelerates the reductive dissolution of ferric iron minerals by way of an indirect mechanism, in which bacterial reduction of soluble ferric iron causes a shift in equilibrium between solid phase (mineral) and soluble ferric iron, thereby causing further dissolution of the mineral.

ISSN:0149-0451    

DOI:10.1080/01490450050121161

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490450050121170

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The role of sulfate-reducing bacteria (SRB) in the cycling of Fe and S was studied in a young constructed wetland located in Kanata, Ontario, Canada. The wetland is a surface-flow system composed of three consecutive cells. Sediments and water samples were collected over the course of 1 year within each cell. Sediments were analyzed for the presence of SRB (using a lactate-rich medium), whereas surface and porewaters were analyzed for their concentrations of dissolved Fe and sulfate and for pH, Eh, and dissolved organic carbon. Lactate-using SRB were present at all three sites within the wetland, and the populations were largest (1010colony-forming units per gram of sediment) during the cold winter months, where the temperature of the water was 1°C. The presence of high-SRB populations also corresponded to highly anoxic conditions within the sediments and to a decrease of sulfate concentrations, suggesting that cold temperature did not affect the activity of SRB. Our results indicate that Fe and S cycling in the young constructed wetland was active throughout the year, especially in the cold winter months, where large SRB populations were encountered. This suggests that Fe removal in wetlands can be effective in temperate climates, even though the temperature of the water decreases drastically during the winter.

ISSN:0149-0451    

DOI:10.1080/01490450050121189

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Boreal peatlands, a major source of atmospheric CH4, are characterized by a rapidly fluctuating water table position and meter-scale variations in relief. Regional and ecosystem-based studies show that water table position generally controls CH4emission from boreal peatlands by influencing the relative extent of the zones of CH4oxidation and production within the peat profile. We used a combined field and laboratory study to assess the influence of local hydrology on the short-term dynamics of CH4production, oxidation, and emission from sites in an Alaskan boreal peatland that were characterized by temporarily (site LB1A) and permanently (LB2) water-saturated subsurface peat during the thaw season. The two sites contrasted sharply with respect to the dynamics of CH4cycling. Site LB1A, which showed low CH4

ISSN:0149-0451    

DOI:10.1080/01490450050121198

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490450050121206

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor