@article {3117, title = {Carbon cloth stimulates direct interspecies electron transfer in syntrophic co-cultures.}, journal = {Bioresour Technol}, volume = {173}, year = {2014}, month = {2014 Dec}, pages = {82-86}, abstract = {

This study investigated the possibility that the electrical conductivity of carbon cloth accelerates direct interspecies electron transfer (DIET) in co-cultures. Carbon cloth accelerated metabolism of DIET co-cultures (Geobacter metallireducens-Geobacter sulfurreducens and G.metallireducens-Methanosarcina barkeri) but did not promote metabolism of co-cultures performing interspecies H2 transfer (Desulfovibrio vulgaris-G.sulfurreducens). On the other hand, DIET co-cultures were not stimulated by poorly conductive cotton cloth. Mutant strains lacking electrically conductive pili, or pili-associated cytochromes participated in DIET only in the presence of carbon cloth. In co-cultures promoted by carbon cloth, cells were primarily associated with the cloth although the syntrophic partners were too far apart for cell-to-cell biological electrical connections to be feasible. Carbon cloth seemingly mediated interspecies electron transfer between the distant syntrophic partners. These results suggest that the ability of carbon cloth to accelerate DIET should be considered in anaerobic digester designs that incorporate carbon cloth.

}, keywords = {Carbon, Cell Communication, Coculture Techniques, Electric Conductivity, Electron Transport, Geobacter, Materials Testing, Membranes, Artificial, Microbial Consortia, Oxidation-Reduction, Symbiosis}, issn = {1873-2976}, doi = {10.1016/j.biortech.2014.09.009}, author = {Chen, Shanshan and Rotaru, Amelia-Elena and Liu, Fanghua and Philips, Jo and Woodard, Trevor L and Nevin, Kelly P and Lovley, Derek R} } @article {3124, title = {Promoting interspecies electron transfer with biochar.}, journal = {Sci Rep}, volume = {4}, year = {2014}, month = {2014 May 21}, pages = {5019}, abstract = {

Biochar, a charcoal-like product of the incomplete combustion of organic materials, is an increasingly popular soil amendment designed to improve soil fertility. We investigated the possibility that biochar could promote direct interspecies electron transfer (DIET) in a manner similar to that previously reported for granular activated carbon (GAC). Although the biochars investigated were 1000 times less conductive than GAC, they stimulated DIET in co-cultures of Geobacter metallireducens with Geobacter sulfurreducens or Methanosarcina barkeri in which ethanol was the electron donor. Cells were attached to the biochar, yet not in close contact, suggesting that electrons were likely conducted through the biochar, rather than biological electrical connections. The finding that biochar can stimulate DIET may be an important consideration when amending soils with biochar and can help explain why biochar may enhance methane production from organic wastes under anaerobic conditions.

}, keywords = {Charcoal, Coculture Techniques, Electron Transport, Electrons, Ethanol, Geobacter, Methanosarcina barkeri, Soil}, issn = {2045-2322}, doi = {10.1038/srep05019}, author = {Chen, Shanshan and Rotaru, Amelia-Elena and Shrestha, Pravin Malla and Malvankar, Nikhil S and Liu, Fanghua and Fan, Wei and Nevin, Kelly P and Lovley, Derek R} } @article {404, title = {Interspecies electron transfer via hydrogen and formate rather than direct electrical connections in cocultures of Pelobacter carbinolicus and Geobacter sulfurreducens.}, journal = {Appl Environ Microbiol}, volume = {78}, year = {2012}, month = {2012 Nov}, pages = {7645-51}, abstract = {

Direct interspecies electron transfer (DIET) is an alternative to interspecies H(2)/formate transfer as a mechanism for microbial species to cooperatively exchange electrons during syntrophic metabolism. To understand what specific properties contribute to DIET, studies were conducted with Pelobacter carbinolicus, a close relative of Geobacter metallireducens, which is capable of DIET. P. carbinolicus grew in coculture with Geobacter sulfurreducens with ethanol as the electron donor and fumarate as the electron acceptor, conditions under which G. sulfurreducens formed direct electrical connections with G. metallireducens. In contrast to the cell aggregation associated with DIET, P. carbinolicus and G. sulfurreducens did not aggregate. Attempts to initiate cocultures with a genetically modified strain of G. sulfurreducens incapable of both H(2) and formate utilization were unsuccessful, whereas cocultures readily grew with mutant strains capable of formate but not H(2) uptake or vice versa. The hydrogenase mutant of G. sulfurreducens compensated, in cocultures, with significantly increased formate dehydrogenase gene expression. In contrast, the transcript abundance of a hydrogenase gene was comparable in cocultures with that for the formate dehydrogenase mutant of G. sulfurreducens or the wild type, suggesting that H(2) was the primary electron carrier in the wild-type cocultures. Cocultures were also initiated with strains of G. sulfurreducens that could not produce pili or OmcS, two essential components for DIET. The finding that P. carbinolicus exchanged electrons with G. sulfurreducens via interspecies transfer of H(2)/formate rather than DIET demonstrates that not all microorganisms that can grow syntrophically are capable of DIET and that closely related microorganisms may use significantly different strategies for interspecies electron exchange.

}, keywords = {Coculture Techniques, Deltaproteobacteria, Electricity, Electron Transport, Electrons, Formates, Geobacter, Hydrogen, Microbial Interactions}, issn = {1098-5336}, doi = {10.1128/AEM.01946-12}, author = {Rotaru, Amelia-Elena and Shrestha, Pravin M and Liu, Fanghua and Ueki, Toshiyuki and Nevin, Kelly and Summers, Zarath M and Lovley, Derek R} }