Rotaru Lab

University of Southern Denmark

Status: completed (2013-2015)

Danish Science Foundation awarded 2 mil. DKK for research on electric interspecies interactions under methanogenic conditions. 

The major focus of the grant is to discover if the recently discovered microbial interspecies interaction via direct electron transfer is widespread in natural environments. To get to environments where such microbial interactions might possibly happen, I’ve rowed in boats made of wood or rubber and been on board a large Swedish fisherman’s boat. We created labs under the deck, on deck, in metal containers, and inside people’s homes. Got really muddy in the process.


Summary of the proposed project:

Methane, a potent greenhouse gas, is also a cost-efficient energy source generated by microorganisms during waste decomposition. The forces behind bio-CH4 production are microbial interactions based on metabolite exchange between syntrophic bacteria fermenting waste organics, and methanogens recycling the products of the first. So far, H2 was the most studied type of metabolite exchange1. Only recently, researchers discovered a new type of electron exchange by direct electron transfer between species (DIET) and proposed it was widespread in methanogenic environments. Yet, little is known about the environmental significance of this type of electron transfer, so learning if DIET is widespread can help us devise new ways to control CH4 emissions, turning it on/off as desired, and resolving two major predicaments of the 21st century – waste removal and clean energy production.
With the aim of understanding the environmental relevance of direct interspecies electron transfer (DIET), I propose the first comprehensive study of this type of interaction in marine systems and agricultural lands. I would like to explore the possibility of DIET in marine environments using already isolated marine strains capable of direct electron transfer to and from electrodes (electrogens and electrotrophs, respectively), followed by the isolation of novel microorganisms potentially primed to perform syntrophy via “electric interactions” in selected environments. My expertise with strict anaerobic microbiology, syntrophic interactions, bio-(electro)chemistry and molecular microbiology techniques should cover most methodological aspects of the project. I will complement the biogeochemical and microbial ecological expertise at SDU with knowledge about interspecies interactions via different types of electron transfer, the use of conductive materials to stimulate interspecies interactions via DIET, and the identification of major cellular components involved in DIET using molecular tools such as DNA- and RNA-based techniques, metatranscriptomic analysis, confocal, fluorescence and electron microscopy, in collaboration with internationally leading laboratories.

Publications (partially or fully funded by this grant):

  1. Rotaru et al. 2019. Limnetica 38(1):21-40
  2. Rotaru et al. 2018. mBio 9(3): e00226-18
  3. Rotaru and Shrestha. 2016. Frontiers in Microbiology 7:662
  4. Rotaru and Thamdrup 2016. Science 351: 658
  5. Rotaru et al. 2015. Frontiers in Microbiology 6:744
  6. Chen et al. 2014, Bioresource Technology 173: 82-86
  7. Shrestha and Rotaru 2014. Frontiers in Microbiology 7:273