Greenhouse gas as a nutrient: methanotrophic activity in soils of hydrothermal systems

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Abstract

Methane is the most abundant hydrocarbon in the atmosphere and a significant contributor to the radiative forcing with a globalwarming potential about 21 times that of CO2. Methane is released to the atmosphere by a wide number of sources, both naturaland anthropogenic, with the latter being twice as large as the former. Significant amounts of geological methane, produced withinthe Earth’s crust (e.g. volcanic/geothermal areas), are currently released into the atmosphere (48 Tg CH4/y).Microbial oxidation in soils by methanotrophic bacteria contributes to the removal of CH4 from the atmosphere for about 3-9%.Methanotrophs belong to the Gamma- and Alpha-proteobacteria and to the recently discovered acidophilic Verrucomicrobia.Evidence of methanotrophic activity also in soils of volcanic/geothermal areas has been recently revealed, notwithstanding theirharsh environmental conditions (high temperatures, low pH, high concentrations of H2S and NH3).The purpose of our study was to verify the methanotrophic potential and the bacterial diversity of the soils of the main geothermalarea of Pantelleria island (Italy).Close to the fumarolic area (Le Favare) the mean detected temperature is about 90 °C at 30 cm of depth and the mean measuredpH of the soil is about 4.8.Laboratory incubation experiments with soil samples collected at the main exhalative area showed methane consumption valuesof up to 9500 ng/g of dry soil per hour while soils collected outside the geothermal area consumed less than 6 ng/g/h. Geothermalsoils showed their maximum methane consumption in the shallowest part of the soil profile (0-3 cm). Furthermore they showedthe maximum consumption at about 37°C, showing a still recognizable consumption (>20 ng/g/h) at 80°C. These results can beconsidered a clear evidence of the presence of methanotrophs.In order to evaluate the bacterial diversity, soil metagenomic DNA was extracted from Le Favare and analysed using a TemporalTemperature Gradient Electrophoresis (TTGE) analysis of the amplified Bacterial 16S rRNA gene. The amplification ofmetagenomic DNA with primers targeting Proteobacterial and Verrucomicrobial MMO (methane monooxygenase) genes is inprogress. Enrichment cultures on a mineral medium in a CH4-enriched (25%) atmosphere led to the isolation of different strains that are under characterization.
Lingua originaleEnglish
pagine (da-a)P78-P78
Numero di pagine1
RivistaEnvironmental Engineering and Management Journal
Volume11
Stato di pubblicazionePublished - 2012

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