Microbial life in geothermal and volcanic areas

Extreme environments, such as volcanic/geothermal areas, are sites of complex interactions between geosphere and biosphere. Although biotic and abiotic components are strictly related, they were separately studied for long time. , Nowadays, innovative and interdisciplinary approaches are available to explore microbial life thriving in these environments.  Pantelleria island (Italy) hosts a high enthalpy geothermal system characterized by high CH4 and low H2S fluxes. Two selected sites, FAV1 and FAV2, located at the main exhalative area of the island Favara Grande, show similar physical conditions with a surface temperature close to 60?C and a soil gas composition enriched in CH4, H2 and CO2. FAV1 soil is characterized by harsher conditions (pH 3.4 and 12% of H2O content); conversely, milder conditions were recorded at site FAV2 (pH 5.8 and 4% of H2O content). High methanotrophic activity (59.2 nmol g?1 h?1) and wide diversity of methanotrophic bacteria were preliminary  detected at FAV2, while no activity could  be detected at FAV1(1). Our aim was to investigate  how the soil microbial communities of these two close geothermal sites at Pantelleria respond to different geochemical conditions. Bacterial and Archaeal communities of the sites were investigated by MiSeq Illumina sequencing of hypervariable regions of the 16S rRNA gene. More than 33,000 reads were obtained for Bacteria and Archaea from soil samples of the two sites. At FAV1 99% of the bacterial sequences were assigned to four main phyla (Proteobacteria, Firmicutes, Actinobacteria and Chloroflexi). FAV2 sequences were distributed in the same phyla with the exception of Chloroflexi that were represented below 1%. Results indicate a high abundance of thermo-acidophilic chemolithotrophs in site FAV1 dominated by Acidithiobacillus ferrooxidans (25%), Nitrosococcus halophilus (10%), Alicyclobacillus spp. (7%) and the rare species Ktedonobacter racemifer (11%). The bacterial community at FAV2 soil is dominated by the methanotrophs (~40% of the reads) Methylocaldum gracile, Beijerinckia sp. and Methylobacterium sp.. The Archaea assemblages are similar in both sites and dominated by the moderately thermophilic chemolithotrophic ammonia-oxidating candidate species Nitrososphaera gargensis, in the phylum Thaumarchaeota. Volcanic/geothermal activities represent a complex phenomenon, thuis shapeing different and peculiar microbial niches even at adjacent sites. Lower pH, higher water, NH4+ and H2 content are probably the discriminating factors that prevent methanotrophy at FAV1 and favor chemolithotrophy. Site FAV2 hosts an extraordinary diversity of methanotrophs due to large supply of CH4, scarce presence of inhibitors of methanotrophy  (H2S and NH3) and slightly acidic soil pH. This study integrates geochemical and biological information to move a step ahead in the still scarce knowledge on the complex ecology of microbes living in geothermal sites and their interactions with the geosphere. (Oppure: This study integrates geochemical and biological information to move a step forward a more complete knowledge on the complex ecology of microbes living in geothermal sites and their interactions with the geosphere)

Biome: root:Environmental:Terrestrial:Volcanic