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| Titel |
The importance of methanotrophic activity in geothermal soils of Pantelleria island (Italy) |
| VerfasserIn |
Walter D'Alessandro, Antonina Lisa Gagliano, Paola Quatrini, Francesco Parello |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250075822
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| Zusammenfassung |
| Methane is a major contributor to the greenhouse effect, its atmospheric concentration
being more than doubled since the XIX century. Every year 22 Tg of methane are
released to the atmosphere from several natural and anthropogenic sources. Natural
sources include geothermal/volcanic areas but the estimation of the total methane
emission from these areas is currently not well defined since the balance between
emission through degassing and microbial oxidation within the soils is not well
known.
Microbial oxidation in soils contributes globally for about 3-9% to the removal of methane
from the atmosphere and recent studies evidenced methanotrophic activity also in soils of
volcanic/geothermal areas despite their harsh environmental conditions (high temperatures,
low pH and high concentrations of H2S and NH3). Methanotrophs are a diverse group of
bacteria that are able to metabolize methane as their only source of carbon and energy and are
found within the Alpha and Gamma classes of Proteobacteria and within the phylum
Verrucomicrobia.
Our purpose was to study the interaction between methanotrophic communities and the
methane emitted from the geothermally most active site of Pantelleria island (Italy), Favara
Grande, whose total methane emission has been previously estimated in about 2.5
t/a.
Laboratory incubation experiments with soil samples from Favara Grande showed methane
consumption values of up to 9500 ng g-1 dry soil per hour while soils collected outside the
geothermal area consume less than 6 ng g-1 h-1. The maximum consumption was
measured in the shallowest part of the soil profile (1-3 cm) and high values (>100
ng g-1 h-1) were maintained up to a depht of 15 cm. Furthermore, the highest
consumption was measured at 37°C, and a still recognizable consumption (>20 ng
g-1 h-1) at 80°C, with positive correlation with the methane concentration in the
incubation atmosphere. These results can be considered a clear evidence of the
presence of methanotrophs that were investigated by culturing and culture-independent
techniques.
The diversity of proteobacterial methanotrophs was investigated by creating a clone library of
the amplified methane mono-oxygenase encoding gene, pmoA. Clone sequencing indicates
the presence of Gammaproteobacteria in the soils of Favara Grande. Enrichment
cultures, on a mineral medium in a CH4-enriched atmosphere, led to the isolation
of different strains that were identified as Methylocistis spp., which belong to the
Alphaproteobacteria.
The presence of Verrucomicrobia was detected by amplification of pmoA gene using newly
designed primers.
Soils from Favara Grande show therefore the largest spectrum of methanotrophic
microorganisms until now detected in a geothermal environment.
While the presence of Verrucomicrobia in geothermal soils was predictable due to their
thermophilic and acidophilic character, the presence of both Alpha and Gamma
proteobacteria was unexpected. Their presence is limited to the shallowest part of the soil
were temperatures are lower and is probably favored by a soil pH that is not too low
(pH ~5) and their contribution to biological methane oxidation at Pantelleria is
significant.
Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge
of the role of soils in methane emissions in such environments. |
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