Electric interspecies interactions in aquatic environments

A/Prof Amelia-Elena Rotaru
Nordic Center for Earth Evolution, University of Southern Denmark
18 March 2016 - 3:00pm
Rountree Room 356, Level 3, Biological Sciences Building D26

Microbial interspecies interactions with methanogens are central for the release of the greenhouse gas - methane, in natural systems, but also for production of useful “biogas” from waste in anaerobic digesters. This seminar will focus on the recent discovery of an unusual type of microbial interspecies interactions via direct electric contacts between Geobacter and Methanosarcinales, which is relevant for anaerobic digestion. Only in co-culture with methanogens belonging to Methanosarcinales, Geobacter can metabolize ethanol in the absence of its usual electron acceptors. Geobacter releases electrons directly via an extracellular network of electrically-conductive cell surface structures - pili and cytochromes. Methanosarcinales cells retrieve electrons by an unknown direct electron-uptake mechanism, to reduce CO2 to methane. This mechanism is now under investigation. Interestingly, conductive materials were shown to stimulate DIET metabolism in co-cultures and in manmade systems including rice paddies and anaerobic digesters. Where else could DIET occur in the environment? Using conductive minerals and labelled isotope probing, evidence for DIET in marine and lake sediments is presented, showing that DIET could partake in methane discharge in natural aquatic systems.

Image: A false-colour transmission electron micrograph of Methanosaeta harundinacea cells. This methanogen is capable of direct interspecies electron transfer with Geobacter metallireducens.
Photo credit: Amelia-Elena Rotaru and Dale Calaghan at UMass Amherst.

Biography: Amelia-Elena Rotaru is recently appointed Assistant Professor at the University of Southern Denmark. In her research group they are searching for solutions to harness microbial metabolism in order to produce fossil fuel free renewable resources and control harmful microbial processes.

Previously, A/Prof Rotaru worked as a postdoc on direct interspecies interactions at the University of Massachusetts Amherst, and biorecovery of rare metals from waste at the University of Aarhus.  She did her PhD at the Max Planck Institute for Marine Microbiology in Bremen, Germany – studying anaerobic biodegradation of hydrocarbons. Part of her PhD was dedicated to syntrophic interactions - a topic which she is still exploring today.