title: Expanding the verrucomicrobial methanotrophic world: description of three novel species of Methylacidimicrobium gen. nov.
abstract: Methanotrophic Verrucomicrobia have been found in geothermal environments characterized by high temperatures and low pH values. However, it has recently been hypothesized that methanotrophic Verrucomicrobia could be present under a broader range of environmental conditions. Here we describe the isolation and characterization of three new species of mesophilic acidophilic verrucomicrobial methanotrophs from a volcanic soil in Italy. The three new species showed 97% to 98% 16S rRNA gene identity to each other but were related only distantly (89% to 90% on the 16S rRNA level) to the thermophilic genus Methylacidiphilum. We propose the new genus Methylacidimicrobium, including the novel species Methylacidimicrobium fagopyrum, Methylacidimicrobium tartarophylax, and Methylacidimicrobium cyclopophantes. These mesophilic Methylacidimicrobium spp. were more acid tolerant than their thermophilic relatives; the most tolerant species, M. tartarophylax, still grew at pH 0.5. The variation in growth temperature optima (35 to 44°C) and maximum growth rates (µmax; 0.013 to 0.040 h(-1)) suggested that all species were adapted to a specific niche within the geothermal environment. All three species grew autotrophically using the Calvin cycle. The cells of all species contained glycogen particles and electron-dense particles in their cytoplasm as visualized by electron microscopy. In addition, the cells of one of the species (M. fagopyrum) contained intracytoplasmic membrane stacks. The discovery of these three new species and their growth characteristics expands the known diversity of verrucomicrobial methanotrophs and shows that they are present in many more ecosystems than previously assumed.
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, the Netherlands.
authors.forename: Muriel C F
authors.initials: MC
authors.lastname: van Teeseling
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, the Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Pol
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, the Netherlands.
authors.forename: Harry R
authors.initials: HR
authors.lastname: Harhangi
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, the Netherlands.
authors.forename: Sietse
authors.initials: S
authors.lastname: van der Zwart
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, the Netherlands.
authors.forename: Mike S M
authors.initials: MS
authors.lastname: Jetten
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, the Netherlands h.opdencamp@science.ru.nl.
authors.forename: Huub J M
authors.initials: HJ
authors.lastname: Op den Camp
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, the Netherlands.
authors.forename: Laura
authors.initials: L
authors.lastname: van Niftrik
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure; D016000:Cluster Analysis; D003593:Cytoplasm / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007558:Italy; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013696:Temperature; D061327:Verrucomicrobia / Q000145:classification* / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S