Metabolic Diversity and Activity of Heterotrophic Bacteria in Ground Water

Abstract

The number and metabolic diversity of bacteria were studied in groundwaters collected in the United States and Canada. Bacterial numbers were determined by acridine orange direct counts, viable plate counts and 14C most‐probable‐number counts. Metabolic diversity was determined by heterotrophic activity and biodegradation potential assays using several classes of natural and xenobiotic substrates. Rates of metabolism in diversity studies (uptake and/or mineralization to carbon dioxide) were measured by radiotracer techniques and rate data were analyzed by nonlinear regression models to generate appropriate kinetic constants. Overall, the density and activity of groundwater bacteria were comparable to values reported for oligotrophic marine and freshwater systems. Bacterial numbers ranged from approximately 102 to 106 cells/ml, depending on the enumeration technique used and the particular sample tested. Turnover times for natural compounds in heterotrophic activity assays (i.e., glucose, amino acids) ranged from less than 100 to more than 2,000 h. Degradation half‐lives for xenobiotic and natural substrates in biodegradation potential studies exhibited a comparable range of values. In general, our results indicate that groundwater bacteria have the potential to metabolize several classes of natural and xenobiotic substrates, although at reduced rates compared with those of surface water systems.

A comparison of microbial community characteristics among petroleum-contaminated and uncontaminated subsurface soil samples

“…These results indicated that a sizable microbial community was present in each sample tested. The AODCs determined for the pristine and uncontaminated samples in this study were approximately on the same order of magnitude as those reported in studies of other uncontaminated aquifer samples, with approximately the same amount of intersample variation [5,16,36,44]. The variation in the AODC populations enumerated from the contaminated samples exhibited a larger amount of intersample variation, which is also observed in other studies of contaminated aquifer samples [6,18,34,43].…”

Mineralization of monosubstituted aromatic compounds in unsaturated and saturated subsurface soils

“…Ward (1985) reported half-lives for benzoic acid of 0.3 days in aerobic and 0.8 days in anaerobic subsurface soils in a septic-tank tile field. Ventullo and Larson (1985) found a half-life for benzoic acid of 1.08 days in groundwater. Benzoic acid half-lives in the present study ranged from 0.4 to 3.2 days.…”

“…Wilson et al (1983a, 19836) demonstrated the ability of microbes in shallow subsurface soil to degrade toluene, and to a lesser degree styrene and chlorobenzene, based upon their disappearance in biologically active samples. Benzoic acid has been shown to be rapidly mineralized-in ground water (Ventullo and Larson 1985) and in anaerobic and aerobic subsurface soils (Ward 1985). Dobbins et al (1987) showed that mineralization potential for phenol varied greatly as a function of soil type and subsurface horizon.…”

Microbial biodiversity in groundwater ecosystems

“…, 1991), or could metabolise xenobiotics not normally occurring in their original environment (e.g. Ventullo & Larson, 1985). In an initiative to archive subsurface microbial biodiversity and promote general access to this genetic resource, the US DOE founded the Subsurface Microbial Culture Collection (SMCC) in 1986 (Balkwill, 1993).…”