ena-STUDY-RADBOUD UNIVERSITY NIJMEGEN-17-03-2020-10:20:37:920-10
A novel Methane and Hydrogen oxidizing Verrucomicrobia species from Pantelleria, Italy
The Favara Grande is a volcanic area in Pantelleria Island characterized by acidic pH (5-3), high temperatures (60 °C) and gas emissions mainly consisting of CH4, H2 and CO2. Based on its geochemical features, the Favara Grande could represent a hotspot for the growth of verrucomicrobial methanotrophs, which are usually found in volcanic ecosystems and need rare earth elements for growth. In this study, we used soil samples from Pantelleria to enrich for novel methanotrophs. The enrichment cultures were incubated at 50 and 60 °C with medium at pH 3 and 5. From these cultures we isolated a new Verrucomicrobia species, for which we propose the name of Methylacidimicrobium thermophilum A8. The genome of strain A8 was sequenced and the gene expression analyzed by transcriptome analysis. Its physiology was investigated by calculating the growth rate, the affinity constant for CH4 and by testing the ability of oxidizing different substrates. In this study we show that this novel metanotroph is able to grow optimally in a pH range of 3 to 5 at 50 °C, representing the first thermophilic strain of the genus Methylacidimicrobium. Furthermore, it exhibited a growth rate of 0.05 h-1 (doubling time ~13 hours) and a Km(app) for methane of 8 ± 1 µM. Transcriptome analysis revealed that methane oxidation at maximum growth rate was carried out by PmoCAB2 and XoxF1 type methanol dehydrogenase. Finally, strain A8 encoded a type 1b Ni-Fe hydrogenase that allowed hydrogen consumption up to 10 µM oxygen. Our results provide more evidence about the characteristics and adaptations of verrucomicrobial methanotrophs in volcanic environments and add a new thermophilic strain to genus Methylacidimicrobium, thus far regarded as mesophilic.
The Favara Grande is a volcanic area in Pantelleria Island characterized by acidic pH (5-3), high temperatures (60 °C) and gas emissions mainly consisting of CH4, H2 and CO2. Based on its geochemical features, the Favara Grande could represent a hotspot for the growth of verrucomicrobial methanotrophs, which are usually found in volcanic ecosystems and need rare earth elements for growth. In this study, we used soil samples from Pantelleria to enrich for novel methanotrophs. The enrichment cultures were incubated at 50 and 60 °C with medium at pH 3 and 5. From these cultures we isolated a new Verrucomicrobia species, for which we propose the name of Methylacidimicrobium thermophilum A8. The genome of strain A8 was sequenced and the gene expression analyzed by transcriptome analysis. Its physiology was investigated by calculating the growth rate, the affinity constant for CH4 and by testing the ability of oxidizing different substrates. In this study we show that this novel metanotroph is able to grow optimally in a pH range of 3 to 5 at 50 °C, representing the first thermophilic strain of the genus Methylacidimicrobium. Furthermore, it exhibited a growth rate of 0.05 h-1 (doubling time ~13 hours) and a Km(app) for methane of 8 ± 1 µM. Transcriptome analysis revealed that methane oxidation at maximum growth rate was carried out by PmoCAB2 and XoxF1 type methanol dehydrogenase. Finally, strain A8 encoded a type 1b Ni-Fe hydrogenase that allowed hydrogen consumption up to 10 µM oxygen. Our results provide more evidence about the characteristics and adaptations of verrucomicrobial methanotrophs in volcanic environments and add a new thermophilic strain to genus Methylacidimicrobium, thus far regarded as mesophilic.