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Author(s): Rafael Laso-Prez [1, 2]; Gunter Wegener (corresponding author) [1, 2, 3]; Katrin Knittel [1]; Friedrich Widdel [1]; Katie J. Harding [1]; Viola Krukenberg [1, 2]; Dimitri V. Meier [1]; [...], The anaerobic formation and oxidation of methane involve unique enzymatic mechanisms and cofactors, all of which are believed to be specific for C[sub.1]-compounds. Here we show that an anaerobic thermophilic enrichment culture composed of dense consortia of archaea and bacteria apparently uses partly similar pathways to oxidize the C[sub.4] hydrocarbon butane. The archaea, proposed genus Candidatus Syntrophoarchaeum, show the characteristic autofluorescence of methanogens, and contain highly expressed genes encoding enzymes similar to methyl-coenzyme M reductase. We detect butyl-coenzyme M, indicating archaeal butane activation analogous to the first step in anaerobic methane oxidation. In addition, Ca. Syntrophoarchaeum expresses the genes encoding -oxidation enzymes, carbon monoxide dehydrogenase and reversible C[sub.1] methanogenesis enzymes. This allows for the complete oxidation of butane. Reducing equivalents are seemingly channelled to HotSeep-1, a thermophilic sulfate-reducing partner bacterium known from the anaerobic oxidation of methane. Genes encoding 16S rRNA and methyl-coenzyme M reductase similar to those identifying Ca. Syntrophoarchaeum were repeatedly retrieved from marine subsurface sediments, suggesting that the presented activation mechanism is naturally widespread in the anaerobic oxidation of short-chain hydrocarbons.

Author(s): Song-Can Chen [sup.1] [sup.2] , Niculina Musat [sup.1] , Oliver J. Lechtenfeld [sup.3] , Heidrun Paschke [sup.3] , Matthias Schmidt [sup.1] , Nedal Said [sup.1] , Denny Popp [sup.4] [...], Ethane is the second most abundant component of natural gas in addition to methane, and--similar to methane--is chemically unreactive. The biological consumption of ethane under anoxic conditions was suggested by geochemical profiles at marine hydrocarbon seeps.sup.1-3, and through ethane-dependent sulfate reduction in slurries.sup.4-7. Nevertheless, the microorganisms and reactions that catalyse this process have to date remained unknown.sup.8. Here we describe ethane-oxidizing archaea that were obtained by specific enrichment over ten years, and analyse these archaea using phylogeny-based fluorescence analyses, proteogenomics and metabolite studies. The co-culture, which oxidized ethane completely while reducing sulfate to sulfide, was dominated by an archaeon that we name 'Candidatus Argoarchaeum ethanivorans'; other members were sulfate-reducing Deltaproteobacteria. The genome of Ca. Argoarchaeum contains all of the genes that are necessary for a functional methyl-coenzyme M reductase, and all subunits were detected in protein extracts. Accordingly, ethyl-coenzyme M (ethyl-CoM) was identified as an intermediate by liquid chromatography-tandem mass spectrometry. This indicated that Ca. Argoarchaeum initiates ethane oxidation by ethyl-CoM formation, analogous to the recently described butane activation by 'Candidatus Syntrophoarchaeum'.sup.9. Proteogenomics further suggests that oxidation of intermediary acetyl-CoA to CO.sub.2 occurs through the oxidative Wood-Ljungdahl pathway. The identification of an archaeon that uses ethane (C.sub.2H.sub.6) fills a gap in our knowledge of microorganisms that specifically oxidize members of the homologous alkane series (C.sub.nH.sub.2n+2) without oxygen. Detection of phylogenetic and functional gene markers related to those of Ca. Argoarchaeum at deep-sea gas seeps.sup.10-12 suggests that archaea that are able to oxidize ethane through ethyl-CoM are widespread members of the local communities fostered by venting gaseous alkanes around these seeps. An archaeon, 'Candidatus Argoarchaeum ethanivorans', which is involved in the oxidation of ethane observed in anoxic marine habitats, is identified and metabolically characterized.

Many archaea produce FtsZ that appears to function in cell division (4-8). However, unlike bacteria, archaeal genomes frequently contain additional genes belonging to the FtsZ/tubulin superfamily (9). These genes are [...], Tubulin is a major component of the eukaryotic cytoskeleton, controlling cell shape, structure and dynamics, whereas its bacterial homologue FtsZ establishes the cytokinetic ring that constricts during cell division (1,2). How such different roles of tubulin and FtsZ evolved is unknown. Studying Archaea may provide clues as these organisms share characteristics with Eukarya and Bacteria (3). Here we report the structure and function of proteins from a distinct family related to tubulin and FtsZ, named CetZ, which co-exists with FtsZ in many archaea. CetZ X-ray crystal structures showed the FtsZ/tubulin superfamily fold, and one crystal form contained sheets of protofilaments, suggesting a structural role. However, inactivation of CetZ proteins in Haloferax volcanii did not affect cell division. Instead, CetZ1 was required for differentiation of the irregular plate-shaped cells into a rod-shaped cell type that was essential for normal swimming motility. CetZ1 formed dynamic cytoskeletal structures in vivo, relating to its capacity to remodel the cell envelope and direct rod formation. CetZ2 was also implicated in H. volcanii cell shape control. Our findings expand the known roles of the FtsZ/ tubulin superfamily to include archaeal cell shape dynamics, suggesting that a cytoskeletal role might predate eukaryotic cell evolution, and they support the premise that a major function of the microbial rod shape is to facilitate swimming.

Anaerobic oxidation of methane (AOM) is critical for controlling the flux of methane from anoxic environments. AOM coupled to iron (1),manganese (1) and sulphate (2) reduction have been demonstrated in [...]

Author(s): Anthony Poole [1]; David Penny [2] [illus. 1] In the absence of direct evidence, science should proceed cautiously with conjecture. Geologist Charles Lyell (1797-1875) warned us not to proceed [...]