Unravelling the molecular basis of the anaerobic degradation of hydrocarbons in archaea

PhD behind the papers Seminar Series

  • Datum: 26.11.2018
  • Uhrzeit: 13:15
  • Vortragende(r): Rafael Laso Perez
  • MPI for Marine Microbiology, Bremen
  • Ort: MPI for Terrestrial Microbiology
  • Raum: Lecture hall
  • Gastgeber: PhD Representatives
  • Kontakt: tarryn.miller@mpi-marburg.mpg.de

Crude oil and natural gas are formed due to the degradation of the organic matter in deep subsurface layers. From there, they can migrate towards the sediment surface, where they represent an energy source for microbial communities. Anaerobic methanotrophic archaea (ANME) are the main responsible of anaerobic oxidation of methane in anoxic environments. For methane oxidation, they use a reversal of the methanogenesis, whose key enzyme is the methyl-coenzyme M reductase (MCR). However, little is known about the role of archaea in the anaerobic oxidation of other hydrocarbons. The aim of my research is to shed light on the role of archaea in anaerobic hydrocarbon degradation. For that we investigated an anaerobic butane-degrading thermophilic enrichment derived from the Guaymas Basin. This enrichment is dominated by consortia of archaea and bacteria. The archaea represent two strains of the newly described clade Candidatus Syntrophoarchaeum. Using meta-omics approaches, we discovered that Ca. Syntrophoarchaeum use before uncharacterized divergent MCRs to activate butane. The produced butyl-CoM units are then fully oxidized using a combination of different pathways and the reducing equivalents are transferred to the partner bacteria for sulfate reduction. Additionally, we also study environmental sediment samples from oil seeps of the Gulf of Mexico. There, several archaeal clades were present including ANME and other undescribed groups like archaea from the D-C06 clade, which were especially abundant and we could visualize in oil droplets without any associated bacteria. Metagenomic analyses revealed that D-C06 had the machinery for alkane degradation similar to Ca. Syntrophoarchaeum, including a divergent mcr gene. Strikingly they also contained a complete methanogenesis pathway with a canonical mcr copy. Therefore, we hypothesize that D-C06 are degrading hydrocarbons coupled to methane production in a single cell. In summary, my research describes a novel pathway in archaea to degrade hydrocarbons anaerobically using highly divergent MCRs that are capable to activate multi-carbon alkanes.

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