Heterotrophic denitrification potential as an adaptive response in groundwater bacteria

Abstract

The denitrification rate of bacteria indigenous to aquifers with different nitrate concentrations was investigated. The objective was to test how high nitrate loads affect community composition and select for enhanced nitrate reduction rates among denitrifying strains. Groundwater bacteria were isolated from two aquifers with high in situ concentrations of nitrate (24.1 and 35.2 mg NO3−‐N 1−1) and one aquifer with a lower in situ concentration (6.3 mg NO3−‐N 1−1). The isolates were characterized with respect to 15 colony and cell morphological and 8 physiological features. The frequency of heterotrophic denitrifiers of all isolated strains was 45–50% in the nitrate contaminated aquifers compared to slightly more than 20% in the uncontaminated aquifer. Kinetics of nitrate reduction were measured by using progress curves ot nitrous oxide production. Bacterial respiration was measured to determine whether proposed differences in denitrification rates were due to differences in carbon utilization. Strains from the aquifers with enhanced nitrate concentrations showed shorter lag periods and higher growth rates than strains from the aquifer with low nitrate concentration. Denitrification rates for unamended incubations varied between 0.10 and 0.42 ml cells−1 day−1 and between 0.42 and 2.10 ml cells−1 day−1 for the glucose amended incubations. The average denitrification rate for the strains from the contaminated sites was 2‐fold higher than for the strains from the uncontaminated site, and glucose amendment increased the difference to 2.5‐fold. The differences in rates were not explained by differences in carbon utilization. The strains from the contaminated sites reduced more nitrate per unit of carbon dioxide produced than the strains from the uncontaminated aquifer. This suggests that strains in soils which have been heavily N‐fertilized may have developed denitrification reductases with optimum activities at high in situ concentrations of nitrate.

Effects of Aquifer Travel Time on Nitrogen Transport to a Coastal Embayment

“…Method 2 was further divided into carbon-limited and carbon-unlimited cases. (1) The higher kinetic parameter values (K NO 3 and V max ) for septic systems compared to nonseptic locations are consistent with other studies, suggesting that denitrifying bacterial populations, growth rates, and activities increase with increasing nitrate concentration (Bengtsson and Bergwall 1995;King and Nedwell 1987 (Almeida et al 1995;Dincer and Kargi 2000;Jorgensen et al 1995;Kornaros et al 1997; Kornaros and Lyberatos 1998; Thomas et al 1994;Wang et al 1995). Many studies mea-sure denitrification kinetic parameters in laboratory incubations under much higher nitrate concentrations than found in this Cape Cod ground water system; when normalized to account for lower denitrifying populations in ground water conditions, reported V max more closely approximate these calculated values (Pabich 2000;Pabich et al in press).…”

Methodology to Increase the Efficiency of the Mineral Water Extraction Process

“…A technical scheme for geological development is necessary and justifies a rational development method [31][32][33]. In countries such as the USA, Japan, Italy, and Germany, achievements have been recorded regarding the use of hydromineral raw materials and the extraction of rare elements and mineral salts [34,35]. Worldwide, the USA is in first place for the production of hydromineral raw materials (thousand tons/year): the USA's production of lithium is about 16, its production of bromine is up to 190, its production of magnesium oxide is up to 750, and its production of table salt is about 16,000; Japan's production of iodine is up to 7; and Italy's production of borates is about 35 [36].…”

Production of Inorganic Carbon From Aquatic Macrophytes by Solar Radiation

“…Measurements of carbon dioxide (CO 2 ) were performed by gas chromatography (Varian model 3700 [Varian Associates, Palo Alto, California, USA]), equipped with a thermal conductivity detector (Bengtsson and Bergwall 1995). An amount from 190 to 210 mg dry mass (DM) of detritus was placed in quartz tubes (inner diameter ϭ 40 mm, length ϭ 200 mm, volume ϭ 190 mL) with ground glass stoppers.…”