David L. Balkwill

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An uncontaminated subsurface aquifer sediment contains a sparse microbial community consisting primarily of coccobacillary bacteria of relatively uniform size which can be counted directly with appropriate staining. The morphological simplicity and the relatively decreased cell numbers, when compared with surface soils and sediments, make the subsurface an(More)
The bacterial microflora of two shallow aquifers (saturated subsurface zones) in Oklahoma was characterized by direct observation with light and electron microscopy, by plating, and by examination of colony morphology and distribution. Isolated bacterial strains were also examined. Total cell counts varied only slightly (2.9 x 10 to 9.8 x 10 g [dry wt])(More)
Previous studies have demonstrated that metal-reducing microorganisms can effectively promote the precipitation and removal of uranium from contaminated groundwater. Microbial communities were stimulated in the acidic subsurface by pH neutralization and addition of an electron donor to wells. In single-well push-pull tests at a number of treated sites,(More)
A novel solvent-producing, anaerobic clostridium, strain P7(T), was isolated from sediment from an agricultural settling lagoon after enrichment with CO as the substrate. The metabolism of this Gram-positive, motile, spore-forming rod was primarily acetogenic. Acetate, ethanol, butyrate and butanol were the end-products of metabolism. Strain P7(T) grew on(More)
A strain of anaerobic, syntrophic, propionate-oxidizing bacteria, strain LYPT (= OCM 661T; T = type strain), was isolated and proposed as representative of a new genus and new species, Smithella propionica gen. nov., sp. nov. The strain was enriched from an anaerobic digestor and isolated. Initial isolation was as a monoxenic propionate-degrading co-culture(More)
Methanogenium frigidum sp. nov. was isolated from the perennially cold, anoxic hypolimnion of Ace Lake in the Vesfold Hills of Antarctica. The cells were psychrophilic, exhibiting most rapid growth at 15 degrees C and no growth at temperatures above 18 to 20 degrees C. The cells were irregular, nonmotile coccoids (diameter, 1.2 to 2.5 microns) that occurred(More)
Bacillus infernus sp. nov. was isolated from ca. 2,700 m below the land surface in the Taylorsville Triassic Basin in Virginia. B. infernus was a strict anaerobe that grew on formate or lactate with Fe(III), MnO2, trimethylamine oxide, or nitrate (reduced to nitrite) as an electron acceptor, and it also grew fermentatively on glucose. Type strain TH-23 and(More)
For extremely ionizing radiation-resistant bacteria, survival has been attributed to protection of proteins from oxidative damage during irradiation, with the result that repair systems survive and function with far greater efficiency during recovery than in sensitive bacteria. Here we examined the relationship between survival of dry-climate soil bacteria(More)
Sediments from a high-level nuclear waste plume were collected as part of investigations to evaluate the potential fate and migration of contaminants in the subsurface. The plume originated from a leak that occurred in 1962 from a waste tank consisting of high concentrations of alkali, nitrate, aluminate, Cr(VI), (137)Cs, and (99)Tc. Investigations were(More)
Iron(III)-reducing bacteria have been demonstrated to rapidly catalyze the reduction and immobilization of uranium(VI) from contaminated subsurface sediments. Thus, these organisms may aid in the development of bioremediation strategies for uranium contamination, which is prevalent in acidic subsurface sediments at U.S. government facilities.(More)