Ethane-feeding archaea's preference for their favored meal

The Paul Scherrer Institute in Switzerland has made a significant breakthrough in the understanding of alkane metabolism, with a team of researchers led by Thomas Spatzal, Oliver Einsle, and Daniel Sippel studying the developments in the tunnel structure of the ethane-fixing enzyme.

The study, titled "Ethanoperedens thermophilum: A New Archaeon from Hydrothermal Vents That Grows on Ethane", published in Science, reveals that the ethane-degrading microbes specialize in ethane capture at geothermally active seeps. The microbes, found at hydrothermal vents of the Guaymas Basin at a water depth of 2,000 meters in the Gulf of California, were named Ethanoperedens thermophilum, meaning "heat-loving ethane-eater".

The ethane-fixing enzyme contains a unique tunnel connecting the exterior to the catalytic chamber, a feature not found in any characterized similar enzymes. This tunnel is maintained and stabilized by modified amino acids and additional extensions. The enzyme responsible for ethane fixation also has a larger catalytic chamber than the one capturing methane.

The first step in ethane degradation is now better understood due to this work, as it is the only source of energy for these archaea. A protein responsible for the methylations in the cofactor is only found in ethane-consuming microbes, further highlighting the unique nature of this enzyme.

Gunter Wegener, a researcher from the Max Planck Institute for Marine Microbiology, where the discovery was made, suggests that the activation of longer alkanes like propane and butane could require similar enzymes. The research team plans to investigate the specific features of the enzymes that catalyze the activation of propane and butane as their next step.

The study's conclusion emphasizes that while the understanding of the whole ethane degradation process is still in progress, the discovery of the ethane-degrading enzyme's specific traits is a significant step forward. The team's findings are accessible via the DOI 10.1126/science.abg1765.

The enzyme responsible for ethane fixation is similar to the enzyme responsible for methane degradation/generation, suggesting a common evolutionary origin. Previous research indicates that the activation of longer alkanes requires similar enzymes. The ethane-degrading enzyme, however, has specific traits that recognize ethane rather than other alkanes.

This discovery not only broadens our understanding of alkane metabolism but also opens up possibilities for future research in bioenergy and bioremediation. The faster growth rate of ethane-eating microbes compared to methane-eating microbes could potentially lead to quicker biomass production, making them valuable in these fields.