报告人： Gunter Wagner, Max Planck Institute for Marine Microbiology, Bremen, Germany
Saturated hydrocarbons are attractive energy and carbon sources for microorganisms, but the knowledge on anaerobic hydrocarbon oxidizers that display the primary sink of these compounds in marine environments is sparse. My team works on multispecies hydrocarbon-oxidizing consortia that we cultivate primarily from gas-rich hydrothermal vents such as found in the Guaymas Basin, Gulf of California. Our general workflow is to supply slurries prepared from heated sediments with specific hydrocarbon compounds as sole energy substrate and sulfate as terminal electron acceptor. The supply of methane yielded consortia of ANME-1 archaea and the before undescribed partner bacterium Ca. Desulfofervidus auxilii. Methane is activated by the archaea in methyl-coenzyme M reductases and the product methyl-CoM reductase is fully oxidized on the methanogenesis pathway. Experiments and microscopic methods located sulfate reduction in the partner bacteria. They retrieve reducing equivalents by direct interspecies electron transfer from the ANME. The involved biochemical and electron transfer mechanisms were thought to be restricted to the C1-compound methane. Recently however, we yielded anaerobic thermophilic enrichment cultures that oxidize the C4-compound butane, but are dominated by the before undescribed Ca. Syntrophoarchaeum. Surprisingly, Syntrophoarchaeum contains highly divergent MCR types that are allow activation of butane via alkyl-CoM formation, but like ANME archaea, it forms consortia with the Desulfofervidus auxilii. Now we enriched additional archaeal strains related to Syntrophoarchaeum that oxidize longer hydrocarbons such as pentane and hexane, and we also enriched archaea that grow on ethane. Metabolite analysis confirms alkyl-CoM formation as general hydrocarbon activation mechanism in these organisms, and syntrophy as underlying principle for their growth with bacterial partners. So far cultivation of C2+-hydrocarbon oxidizing archaea has only been possible at elevated temperatures, however presence of phylogenetic marker genes and divergent mcr types in cold seeps suggest an important role of these consortia-forming organisms in a wide range of gas-rich habitats. The understanding of archaeal hydrocarbon-degradation may, in future, allow bioengineers of biogenic short-chain hydrocarbon production, analogous to methane production in methanogens.
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