title: Clonothrix fusca Roze 1896, a filamentous, sheathed, methanotrophic gamma-proteobacterium.
abstract: Crenothrix polyspora Cohn 1870 and Clonothrix fusca Roze 1896 are two filamentous, sheathed microorganisms exhibiting complex morphological differentiation, whose phylogeny and physiology have been obscure for a long time due to the inability to cultivate them. Very recently, DNA sequencing data from uncultured C. polyspora-enriched material have suggested that Crenothrix is a methane-oxidizing gamma-proteobacterium (39). In contrast, the possible ecological function of C. fusca, originally considered a developmental stage of C. polyspora, is unknown. In this study, temporal succession of two filamentous, sheathed microorganisms resembling Cohn's Crenothrix and Roze's Clonothrix was observed by analyzing the microbial community of an artesian well by optical microscopy. Combined culture-based and culture-independent approaches enabled us to assign C. fusca to a novel subgroup of methane-oxidizing gamma-proteobacteria distinct from that of C. polyspora. This assignment was supported by (i) methane uptake and assimilation experiments, (ii) ultrastructural data showing the presence in C. fusca cytoplasm of an elaborate membrane system resembling that of methanotrophic gamma-proteobacteria, and (iii) sequencing data demonstrating the presence in its genome of a methanol dehydrogenase alpha subunit-encoding gene (mxaF) and a conventional particulate methane mono-oxygenase alpha subunit-encoding gene (pmoA) that is different from the unusual pmoA (u-pmoA) of C. polyspora.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università degli Studi di Lecce, Via Monteroni, 73100 Lecce, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Vigliotta
authors.forename: Eliana
authors.initials: E
authors.lastname: Nutricati
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Carata
authors.forename: Salvatore M
authors.initials: SM
authors.lastname: Tredici
authors.forename: Mario
authors.initials: M
authors.lastname: De Stefano
authors.forename: Paola
authors.initials: P
authors.lastname: Pontieri
authors.forename: Domenica Rita
authors.initials: DR
authors.lastname: Massardo
authors.forename: Maria Vittoria
authors.initials: MV
authors.lastname: Prati
authors.forename: Luigi
authors.initials: L
authors.lastname: De Bellis
authors.forename: Pietro
authors.initials: P
authors.lastname: Alifano
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D002462:Cell Membrane / Q000648:ultrastructure; D016000:Cluster Analysis; D003470:Culture Media; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005618:Fresh Water / Q000382:microbiology*; D008697:Methane / Q000378:metabolism; D008772:Methylococcaceae / Q000145:classification* / Q000166:cytology / Q000302:isolation & purification* / Q000502:physiology; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000235:genetics; D010802:Phylogeny; D021122:Protein Subunits / Q000235:genetics; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D012988:Soil Microbiology; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D021122:Protein Subunits; D000429:Alcohol Oxidoreductases; C019641:alcohol dehydrogenase (acceptor); D010105:Oxygenases; C021555:methane monooxygenase; D008697:Methane