title: Methylacidiphilum fumariolicum SolV, a thermoacidophilic 'Knallgas' methanotroph with both an oxygen-sensitive and -insensitive hydrogenase.
abstract: Methanotrophs play a key role in balancing the atmospheric methane concentration. Recently, the microbial methanotrophic diversity was extended by the discovery of thermoacidophilic methanotrophs belonging to the Verrucomicrobia phylum in geothermal areas. Here we show that a representative of this new group, Methylacidiphilum fumariolicum SolV, is able to grow as a real 'Knallgas' bacterium on hydrogen/carbon dioxide, without addition of methane. The full genome of strain SolV revealed the presence of two hydrogen uptake hydrogenases genes, encoding an oxygen-sensitive (hup-type) and an oxygen-insensitive enzyme (hhy-type). The hhy-type hydrogenase was constitutively expressed and active and supported growth on hydrogen alone up to a growth rate of 0.03 h-1, at O2concentrations below 1.5%. The oxygen-sensitive hup-type hydrogenase was expressed when oxygen was reduced to below 0.2%. This resulted in an increase of the growth rate to a maximum of 0.047 h-1, that is 60% of the rate on methane. The results indicate that under natural conditions where both hydrogen and methane might be limiting strain SolV may operate primarily as a methanotrophic 'Knallgas' bacterium. These findings argue for a revision of the role of hydrogen in methanotrophic ecosystems, especially in soil and related to consumption of atmospheric methane.
authors.affiliation: Department of Microbiology, IWWR, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Sepehr
authors.initials: S
authors.lastname: Mohammadi
authors.affiliation: Department of Microbiology, IWWR, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Pol
authors.affiliation: Department of Microbiology, IWWR, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Theo A
authors.initials: TA
authors.lastname: van Alen
authors.affiliation: Department of Microbiology, IWWR, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Mike Sm
authors.initials: MS
authors.lastname: Jetten
authors.affiliation: Department of Microbiology, IWWR, Radboud University, Heyendaalseweg 135, NL-6525 AJ, Nijmegen, The Netherlands.
authors.forename: Huub Jm
authors.initials: HJ
authors.lastname: Op den Camp
mesh_terms: D002244:Carbon; D002245:Carbon Dioxide; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D016680:Genome, Bacterial; D006864:Hydrogenase / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D008697:Methane; D010100:Oxygen; D010802:Phylogeny; D012988:Soil Microbiology; D061327:Verrucomicrobia / Q000201:enzymology* / Q000235:genetics
chemical_list: D002245:Carbon Dioxide; D002244:Carbon; D006864:Hydrogenase; D008697:Methane; D010100:Oxygen