Abstract
Interspecies exchange of electrons enables a diversity of microbial communities to gain energy from reactions that no one microbe can catalyze. The first recognized strategies for interspecies electron transfer were those that relied on chemical intermediates that are recycled through oxidized and reduced forms. Well-studied examples are interspecies H2 transfer and the cycling of sulfur intermediates in anaerobic photosynthetic communities. Direct interspecies electron transfer (DIET) in which two species establish electrical contact is an alternative. Electrical contacts documented to date include electrically conductive pili, as well as conductive iron minerals and conductive carbon moieties such as activated carbon and biochar. Interspecies electron transfer is central to the functioning of methane-producing microbial communities. The importance of interspecies H2 transfer in many methanogenic communities is clear, but under some circumstances DIET predominates. It is expected that further mechanistic studies and broadening investigations to a wider range of environments will help elucidate the factors that favor specific forms of interspecies electron exchange under different environmental conditions.
Highlights
Interspecies electron transfer plays a key role in the functioning of methane-producing microbial communities, which have a significant impact on the global carbon cycle (Stams and Plugge, 2009; Sieber et al, 2012)
Interspecies electron transfer via H2/formate has been extensively reviewed in recent years (Morris et al, 2013; Schink and Stams, 2013; Sieber et al, 2014)
H2 AND FORMATE AS ELECTRON TRANSFER MOLECULES H2 and formate are important electron transfer molecules that are reported in various methanogenic environments (Schink and Stams, 2006, 2013; Stams and Plugge, 2009), these are described briefly under separate headings below: H2 AS ELECTRON TRANSFER MOLECULE Interspecies electron transfer via H2 was first demonstrated almost four decades ago in a defined co-culture (Bryant et al, 1967) of the “S organism,” which converted ethanol to acetate and H2, only in the presence of Methanobacterium ruminantium, which consumed H2 for the reduction of CO2 to CH4 (Bryant et al, 1967)
Summary
Interspecies electron transfer plays a key role in the functioning of methane-producing microbial communities, which have a significant impact on the global carbon cycle (Stams and Plugge, 2009; Sieber et al, 2012). Interspecies electron transfer via H2/formate has been extensively reviewed in recent years (Morris et al, 2013; Schink and Stams, 2013; Sieber et al, 2014). The generation of H2 is energetically unfavorable at H2 partial pressures above 10−3 bar (Schink and Stams, 2013), syntrophic microorganisms bypass this energetic barrier by coupling the unfavorable H2 production with www.frontiersin.org
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
