@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 {3077,
	title = {Iron Corrosion via Direct Metal-Microbe Electron Transfer.},
	journal = {mBio},
	volume = {10},
	year = {2019},
	month = {2019 May 14},
	abstract = {<p>The concept that anaerobic microorganisms can directly accept electrons from Fe(0) has been controversial because direct metal-microbe electron transfer has previously only been indirectly inferred. Fe(0) oxidation was studied with  strain ACL, an autotrophic strain that was previously shown to grow with electrons derived from a graphite cathode as the sole electron donor. Strain ACL grew with Fe(0) as the sole electron donor and fumarate as the electron acceptor. However, it appeared that at least a portion of the electron transfer was via H produced nonenzymatically from the oxidation of Fe(0) to Fe(II). H, which accumulated in abiotic controls, was consumed during the growth of strain ACL, the cells were predominately planktonic, and genes for the uptake hydrogenase were highly expressed. Strain ACL was constructed to prevent growth on H or formate by deleting the genes for the uptake of hydrogenase and formate dehydrogenases from strain ACL. Strain ACL also grew with Fe(0) as the sole electron donor, but H accumulated in the culture, and cells heavily colonized Fe(0) surfaces with no visible planktonic growth. Transcriptomics suggested that the outer surface -type cytochromes OmcS and OmcZ were important during growth of strain ACL on Fe(0). Strain ACL did not grow on Fe(0) if the gene for either of these cytochromes was deleted. The specific attachment of strain ACL to Fe(0), coupled with requirements for known extracellular electrical contacts, suggest that direct metal-microbe electron transfer is the most likely option for Fe(0) serving as an electron donor. The anaerobic corrosion of iron structures is expensive to repair and can be a safety and environmental concern. It has been known for over 100 years that the presence of anaerobic respiratory microorganisms can accelerate iron corrosion. Multiple studies have suggested that there are sulfate reducers, methanogens, and acetogens that can directly accept electrons from Fe(0) to support sulfate or carbon dioxide reduction. However, all of the strains studied can also use H as an electron donor for growth, which is known to be abiotically produced from Fe(0). Furthermore, no proteins definitely shown to function as extracellular electrical contacts with Fe(0) were identified. The studies described here demonstrate that direct electron transfer from Fe(0) can support anaerobic respiration. They also map out a simple genetic approach to the study of iron corrosion mechanisms in other microorganisms. A better understanding of how microorganisms promote iron corrosion is expected to lead to the development of strategies that can help reduce adverse impacts from this process.</p>},
	keywords = {Anaerobiosis, Corrosion, Cytochromes, Electron Transport, Formate Dehydrogenases, Geobacter, Iron, Oxidation-Reduction, Oxidoreductases, Transcriptome},
	issn = {2150-7511},
	doi = {10.1128/mBio.00303-19},
	author = {Tang, Hai-Yan and Holmes, Dawn E and Ueki, Toshiyuki and Palacios, Paola A and Lovley, Derek R}
}
