Exploring methanotrophic activity in geothermal soils from Pantelleria Island (Italy)

Methane is released to the atmosphere by a wide number of natural (geological and biological) and anthropogenic sources, and is the second most important greenhouse gas after CO2. Microbial oxidation in soils by methanotrophic bacteria contributes to the removal of CH4 from the atmosphere and methanotrophic activity was also detected in volcanic/geothermal areas where degassing of endogenous gases occurs. Our aim is to describe the methanotrophs at the main exhalative area of Le Favare site at Pantelleria Island, where high CH4 consumption (up to 950 ng/g/ per h) was measured. Total soil bacterial diversity was analysed by TTGE of amplified 16S rRNA genes and the diversity of proteobacterial methanotrophs was investigated by creating a clone library of the amplified methane mono-oxygenase encoding genes, pmmoA. Enrichment cultures on a mineral medium in a CH4-enriched atmosphere led to the isolation of different strains that were identified as Methylocistis spp. Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge of the role of such soils in methane emissions.