Recovery of in-situ methanotrophic activity following acetylene inhibition

Methane (CH4) is the second most important greenhouse gas after carbon dioxide (CO2). To understand CH4 cycling, quantitative information about microbial CH4 oxidation in soils is essential. Field methods such as the gas push-pull test (GPPT) to quantify CH4 oxidation are often used in combination with specific inhibitors, such as acetylene (C2H2). Acetylene irreversibly binds to the enzyme methane monooxygenase, but little is known about recovery of CH4 oxidation activity after C2H2 inhibition in situ, which is important when performing several experiments at the same location. To assess recovery of CH4 oxidation activity following C2H2 inhibition, we performed a series of GPPTs over 8 weeks at two different locations in the vadose zone above a petroleum hydrocarbon-contaminated aquifer in Studen, Switzerland. After 4 weeks a maximum recovery of 30% and 50% of the respective initial activity was reached, with a subsequent slight drop in activity at both locations. Likely, CH4 oxidation activity and CH4 concentrations were too low to allow for rapid recovery following C2H2 inhibition at the studied locations. Therefore, alternative competitive inhibitors have to be evaluated for application in conjunction with GPPTs, especially for sites with low activit

Recovery of in-situ methanotrophic activity following acetylene inhibition

Methane (CH4) is the second most important greenhouse gas after carbon dioxide (CO2). To understand CH4 cycling, quantitative information about microbial CH4 oxidation in soils is essential. Field methods such as the gas push-pull test (GPPT) to quantify CH4 oxidation are often used in combination with specific inhibitors, such as acetylene (C2H2). Acetylene irreversibly binds to the enzyme methane monooxygenase, but little is known about recovery of CH4 oxidation activity after C2H2 inhibition in situ, which is important when performing several experiments at the same location. To assess recovery of CH4 oxidation activity following C2H2 inhibition, we performed a series of GPPTs over 8 weeks at two different locations in the vadose zone above a petroleum hydrocarbon-contaminated aquifer in Studen, Switzerland. After 4 weeks a maximum recovery of 30% and 50% of the respective initial activity was reached, with a subsequent slight drop in activity at both locations. Likely, CH4 oxidation activity and CH4 concentrations were too low to allow for rapid recovery following C2H2 inhibition at the studied locations. Therefore, alternative competitive inhibitors have to be evaluated for application in conjunction with GPPTs, especially for sites with low activit

Response of methanotrophic activity and community structure to temperature changes in a diffusive CH4/O2 counter gradient in an unsaturated porous medium

Microbial methane oxidation is a key process in the global methane cycle. In the context of global warming, it is important to understand the responses of the methane-oxidizing microbial community to temperature changes in terms of community structure and activity. We studied microbial methane oxidation in a laboratory-column system in which a diffusive CH4/O2 counter gradient was maintained in an unsaturated porous medium at temperatures between 4 and 20 °C. Methane oxidation was highly efficient at all temperatures, as on average 99 ± 0.5% of methane supplied to the system was oxidized. The methanotrophic community that established in the model system after initial inoculation appeared to be able to adapt quickly to different temperatures, as methane emissions remained low even after the system was subjected to abrupt temperature changes. FISH showed that Type I as well as Type II methanotrophs were probably responsible for the observed activity in the column system, with a dominance of Type I methanotrophs. Cloning and sequencing suggested that Type I methanotrophs were represented by the genus Methylobacter while Type II were represented by Methylocystis. The results suggest that in an unsaturated system with diffusive substrate supply, direct effects of temperature on apparent methanotrophic activity and community may be of minor importance. However, this remains to be verified in the fiel

Recovery of in-situ methanotrophic activity following acetylene inhibition

Abstract Methane (CH 4 ) is the second most important greenhouse gas after carbon dioxide (CO 2 ). To understand CH 4 cycling, quantitative information about microbial CH 4 oxidation in soils is essential. Field methods such as the gas push-pull test (GPPT) to quantify CH 4 oxidation are often used in combination with specific inhibitors, such as acetylene (C 2 H 2 ). Acetylene irreversibly binds to the enzyme methane monooxygenase, but little is known about recovery of CH 4 oxidation activity after C 2 H 2 inhibition in situ, which is important when performing several experiments at the same location. To assess recovery of CH 4 oxidation activity following C 2 H 2 inhibition, we performed a series of GPPTs over 8 weeks at two different locations in the vadose zone above a petroleum hydrocarbon-contaminated aquifer in Studen, Switzerland. After 4 weeks a maximum recovery of 30% and 50% of the respective initial activity was reached, with a subsequent slight drop in activity at both locations. Likely, CH 4 oxidation activity and CH 4 concentrations were too low to allow for rapid recovery following C 2 H 2 inhibition at the studied locations. Therefore, alternative competitive inhibitors have to be evaluated for application in conjunction with GPPTs, especially for sites with low activity

Response of methanotrophic activity and community structure to temperature changes in a diffusive CH4/O2 counter gradient in an unsaturated porous medium

ISSN:0168-6496ISSN:1574-694

Further validation of the HPCD-technique for the evaluation of PAH microbial availability in soil.

There is currently considerable scientific interest in finding a chemical technique capable of predicting bioavailability; non-exhaustive extraction techniques (NEETs) offer such potential. Hydroxypropyl-beta-cyclodextrin (HPCD), a NEET, is further validated through the investigation of concentration ranges, differing soil types, and the presence of co-contaminants. This is the first study to demonstrate the utility of the HPCD-extraction technique to predict the microbial availability to phenanthrene across a wide concentration range and independent of soil-contaminant contact time (123 d). The efficacy of the HPCD-extraction technique for the estimation of PAH microbial availability in soil is demonstrated in the presence of co-contaminants that have been aged for the duration of the experiment together in the soil. Desorption dynamics are compared in co-contaminant and single-PAH contaminated spiked soils to demonstrate the occurrence of competitive displacement. Overall, a single HPCD-extraction technique proved accurate and reproducible for the estimation of PAH bioavailability from soil. (c) 2006 Elsevier Ltd. All rights reserved