@article {3085,
	title = {Potential for Methanosarcina to Contribute to Uranium Reduction during Acetate-Promoted Groundwater Bioremediation.},
	journal = {Microb Ecol},
	volume = {76},
	year = {2018},
	month = {2018 Oct},
	pages = {660-667},
	abstract = {<p>Previous studies of acetate-promoted bioremediation of uranium-contaminated aquifers focused on Geobacter because no other microorganisms that can couple the oxidation of acetate with U(VI) reduction had been detected in situ. Monitoring the levels of methyl CoM reductase subunit A (mcrA) transcripts during an acetate-injection field experiment demonstrated that acetoclastic methanogens from the genus Methanosarcina were enriched after 40~days of acetate amendment. The increased abundance of Methanosarcina corresponded with an accumulation of methane in the groundwater. In order to determine whether Methanosarcina species could be participating in U(VI) reduction in the subsurface, cell suspensions of Methanosarcina barkeri were incubated in the presence of U(VI) with acetate provided as the electron donor. U(VI) was reduced by metabolically active M. barkeri cells; however, no U(VI) reduction was observed in inactive controls. These results demonstrate that Methanosarcina species could play an important role in the long-term bioremediation of uranium-contaminated aquifers after depletion of Fe(III) oxides limits the growth of Geobacter species. The results also suggest that Methanosarcina have the potential to influence uranium geochemistry in a diversity of anaerobic sedimentary environments.</p>},
	keywords = {Acetates, Biodegradation, Environmental, Geobacter, Groundwater, Methane, Methanosarcina, Oxidation-Reduction, Uranium, Water Pollutants, Chemical},
	issn = {1432-184X},
	doi = {10.1007/s00248-018-1165-5},
	author = {Holmes, Dawn E and Orelana, Roberto and Giloteaux, Ludovic and Wang, Li-Ying and Shrestha, Pravin and Williams, Kenneth and Lovley, Derek R and Rotaru, Amelia-Elena}
}
@article {3084,
	title = { Strains Expressing Poorly Conductive Pili Reveal Constraints on Direct Interspecies Electron Transfer Mechanisms.},
	journal = {mBio},
	volume = {9},
	year = {2018},
	month = {2018 Jul 10},
	abstract = {<p>Cytochrome-to-cytochrome electron transfer and electron transfer along conduits of multiple extracellular magnetite grains are often proposed as strategies for direct interspecies electron transfer (DIET) that do not require electrically conductive pili (e-pili). However, physical evidence for these proposed DIET mechanisms has been lacking. To investigate these possibilities further, we constructed  strain Aro-5, in which the wild-type pilin gene was replaced with the  pilin gene that was previously shown to yield poorly conductive pili in  strain Aro-5.  strain Aro-5 did not reduce Fe(III) oxide and produced only low current densities, phenotypes consistent with expression of poorly conductive pili. Like  strain Aro-5,  strain Aro-5 displayed abundant outer surface cytochromes. Cocultures initiated with wild-type  as the electron-donating strain and  strain Aro-5 as the electron-accepting strain grew via DIET. However,  Aro-5/ wild-type cocultures did not. Cocultures initiated with the Aro-5 strains of both species grew only when amended with granular activated carbon (GAC), a conductive material known to be a conduit for DIET. Magnetite could not substitute for GAC. The inability of the two Aro-5 strains to adapt for DIET in the absence of GAC suggests that there are physical constraints on establishing DIET solely through cytochrome-to-cytochrome electron transfer or along chains of magnetite. The finding that DIET is possible with electron-accepting partners that lack highly conductive pili greatly expands the range of potential electron-accepting partners that might participate in DIET. DIET is thought to be an important mechanism for interspecies electron exchange in natural anaerobic soils and sediments in which methane is either produced or consumed, as well as in some photosynthetic mats and anaerobic digesters converting organic wastes to methane. Understanding the potential mechanisms for DIET will not only aid in modeling carbon and electron flow in these geochemically significant environments but will also be helpful for interpreting meta-omic data from as-yet-uncultured microbes in DIET-based communities and for designing strategies to promote DIET in anaerobic digesters. The results demonstrate the need to develop a better understanding of the diversity of types of e-pili in the microbial world to identify potential electron-donating partners for DIET. Novel methods for recovering as-yet-uncultivated microorganisms capable of DIET in culture will be needed to further evaluate whether DIET is possible without e-pili in the absence of conductive materials such as GAC.</p>},
	keywords = {Cytochromes, Electron Transport, Ferric Compounds, Fimbriae, Bacterial, Geobacter, Microbial Interactions, Oxidation-Reduction},
	issn = {2150-7511},
	doi = {10.1128/mBio.01273-18},
	author = {Ueki, Toshiyuki and Nevin, Kelly P and Rotaru, Amelia-Elena and Wang, Li-Ying and Ward, Joy E and Woodard, Trevor L and Lovley, Derek R}
}
