title: Magnetite particles triggering a faster and more robust syntrophic pathway of methanogenic propionate degradation.
abstract: Interspecies electron transfer mechanisms between Bacteria and Archaea play a pivotal role during methanogenic degradation of organic matter in natural and engineered anaerobic ecosystems. Growing evidence suggests that in syntrophic communities electron transfer does not rely exclusively on the exchange of diffusible molecules and energy carriers such as hydrogen or formate, rather microorganisms have the capability to exchange metabolic electrons in a more direct manner. Here, we show that supplementation of micrometer-size magnetite (Fe3O4) particles to a methanogenic sludge enhanced (up to 33%) the methane production rate from propionate, a key intermediate in the anaerobic digestion of organic matter and a model substrate to study energy-limited syntrophic communities. The stimulatory effect most probably resulted from the establishment of a direct interspecies electron transfer (DIET), based on magnetite particles serving as electron conduits between propionate-oxidizing acetogens and carbon dioxide-reducing methanogens. Theoretical calculations revealed that DIET allows electrons to be transferred among syntrophic partners at rates which are substantially higher than those attainable via interspecies H2 transfer. Besides the remarkable potential for improving anaerobic digestion, which is a proven biological strategy for renewable energy production, the herein described conduction-based DIET could also have a role in natural methane emissions from magnetite-rich soils and sediments.
authors.affiliation: Water Research Institute (IRSA), National Research Council (CNR) , via Salaria km 29.300, 00015 Monterotondo (RM), Italy.
authors.forename: Carolina
authors.initials: C
authors.lastname: Cruz Viggi
authors.forename: Simona
authors.initials: S
authors.lastname: Rossetti
authors.forename: Stefano
authors.initials: S
authors.lastname: Fazi
authors.forename: Paola
authors.initials: P
authors.lastname: Paiano
authors.forename: Mauro
authors.initials: M
authors.lastname: Majone
authors.forename: Federico
authors.initials: F
authors.lastname: Aulenta
mesh_terms: D000085:Acetates / Q000378:metabolism; D001105:Archaea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D001419:Bacteria / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D001673:Biodegradation, Environmental / Q000187:drug effects; D002087:Butyrates / Q000378:metabolism; D004058:Diffusion; D004579:Electron Transport / Q000187:drug effects; D052203:Ferrosoferric Oxide / Q000494:pharmacology*; D006859:Hydrogen / Q000737:chemistry; D017404:In Situ Hybridization, Fluorescence; D007700:Kinetics; D008697:Methane / Q000378:metabolism*; D010313:Partial Pressure; D011422:Propionates / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000085:Acetates; D002087:Butyrates; D011422:Propionates; D006859:Hydrogen; D008697:Methane; D052203:Ferrosoferric Oxide