@article {3063,
	title = {Correlation of Key Physiological Properties of  Isolates with Environment of Origin.},
	journal = {Appl Environ Microbiol},
	volume = {87},
	year = {2021},
	month = {2021 Jun 11},
	pages = {e0073121},
	abstract = {<p>It is known that the physiology of  species can differ significantly, but the ecological impact of these differences is unclear. We recovered two strains of  from two different ecosystems with a similar enrichment and isolation method. Both strains had the same ability to metabolize organic substrates and participate in direct interspecies electron transfer but also had major physiological differences. Strain DH-1, which was isolated from an anaerobic digester, used H as an electron donor. Genome analysis indicated that it lacks an Rnf complex and conserves energy from acetate metabolism via intracellular H cycling. In contrast, strain DH-2, a subsurface isolate, lacks hydrogenases required for H uptake and cycling and has an Rnf complex for energy conservation when growing on acetate. Further analysis of the genomes of previously described isolates, as well as phylogenetic and metagenomic data on uncultured  in anaerobic digesters and diverse soils and sediments, revealed a physiological dichotomy that corresponded with environment of origin. The physiology of type I  revolves around H production and consumption. In contrast, type II  species eschew H and have genes for an Rnf complex and the multiheme, membrane-bound -type cytochrome MmcA, shown to be essential for extracellular electron transfer. The distribution of  species in diverse environments suggests that the type I H-based physiology is well suited for high-energy environments, like anaerobic digesters, whereas type II Rnf/cytochrome-based physiology is an adaptation to the slower, steady-state carbon and electron fluxes common in organic-poor anaerobic soils and sediments.  Biogenic methane is a significant greenhouse gas, and the conversion of organic wastes to methane is an important bioenergy process.  species play an important role in methane production in many methanogenic soils and sediments as well as anaerobic waste digesters. The studies reported here emphasize that the genus  is composed of two physiologically distinct groups. This is important to recognize when interpreting the role of  in methanogenic environments, especially regarding H metabolism. Furthermore, the finding that type I  species predominate in environments with high rates of carbon and electron flux and that type II  species predominate in lower-energy environments suggests that evaluating the relative abundance of type I and type II  may provide further insights into rates of carbon and electron flux in methanogenic environments.</p>},
	keywords = {Acetates, Anaerobiosis, Bioreactors, Ecosystem, Electron Transport, Ethanol, Genome, Archaeal, Hydrogen, Methane, Methanosarcina, Phylogeny},
	issn = {1098-5336},
	doi = {10.1128/AEM.00731-21},
	author = {Zhou, Jinjie and Holmes, Dawn E and Tang, Hai-Yan and Lovley, Derek R}
}
@article {3074,
	title = {A Membrane-Bound Cytochrome Enables  To Conserve Energy from Extracellular Electron Transfer.},
	journal = {mBio},
	volume = {10},
	year = {2019},
	month = {2019 Aug 20},
	abstract = {<p>Extracellular electron exchange in  species and closely related  plays an important role in the global carbon cycle and enhances the speed and stability of anaerobic digestion by facilitating efficient syntrophic interactions. Here, we grew  with methanol provided as the electron donor and the humic analogue, anthraquione-2,6-disulfonate (AQDS), provided as the electron acceptor when methane production was inhibited with bromoethanesulfonate. AQDS was reduced with simultaneous methane production in the absence of bromoethanesulfonate. Transcriptomics revealed that expression of the gene for the transmembrane, multiheme, -type cytochrome MmcA was higher in AQDS-respiring cells than in cells performing methylotrophic methanogenesis. A strain in which the gene for MmcA was deleted failed to grow via AQDS reduction but grew with the conversion of methanol or acetate to methane, suggesting that MmcA has a specialized role as a conduit for extracellular electron transfer. Enhanced expression of genes for methanol conversion to methyl-coenzyme M and the Rnf complex suggested that methanol is oxidized to carbon dioxide in AQDS-respiring cells through a pathway that is similar to methyl-coenzyme M oxidation in methanogenic cells. However, during AQDS respiration the Rnf complex and reduced methanophenazine probably transfer electrons to MmcA, which functions as the terminal reductase for AQDS reduction. Extracellular electron transfer may enable the survival of methanogens in dynamic environments in which oxidized humic substances and Fe(III) oxides are intermittently available. The availability of tools for genetic manipulation of  makes it an excellent model microbe for evaluating -type cytochrome-dependent extracellular electron transfer in  The discovery of a methanogen that can conserve energy to support growth solely from the oxidation of organic carbon coupled to the reduction of an extracellular electron acceptor expands the possible environments in which methanogens might thrive. The potential importance of -type cytochromes for extracellular electron transfer to syntrophic bacterial partners and/or Fe(III) minerals in some  was previously proposed, but these studies with  provide the first genetic evidence for cytochrome-based extracellular electron transfer in  The results suggest parallels with Gram-negative bacteria, such as  and  species, in which multiheme outer-surface -type cytochromes are an essential component for electrical communication with the extracellular environment.  offers an unprecedented opportunity to study mechanisms for energy conservation from the anaerobic oxidation of one-carbon organic compounds coupled to extracellular electron transfer in  with implications not only for methanogens but possibly also for  that anaerobically oxidize methane.</p>},
	keywords = {Acetates, Anthraquinones, Cytochromes, Electron Transport, Electrons, Ferric Compounds, Gene Expression Regulation, Archaeal, Gram-Negative Bacteria, Membranes, Mesna, Methane, Methanol, Methanosarcina, Oxidation-Reduction, Oxidoreductases, Transcriptome},
	issn = {2150-7511},
	doi = {10.1128/mBio.00789-19},
	author = {Holmes, Dawn E and Ueki, Toshiyuki and Tang, Hai-Yan and Zhou, Jinjie and Smith, Jessica A and Chaput, Gina and Lovley, Derek R}
}
