Microbial Fuel Factories

An archaeon takes the first steps toward making a liquid fuel from carbon dioxide and hydrogen gas.

Sep 1, 2013
Kate Yandell

EDITOR'S CHOICE IN BIOENGINEERING

ONE CHILL MICROBE: The archaeon Pyrococcus furiosus normally thrives at 100 °C. Culturing it at a lower temperature can minimize metabolic processes that may interfere with engineered pathways.FULVIO314/WIKIMEDIA COMMONS

The paper
M.W. Keller et al., “Exploiting microbial hyperthermophilicity to produce an industrial chemical, using hydrogen and carbon dioxide,” PNAS, 110:5840-45, 2013.

The finding
Genetically engineered microorganisms could be used to produce fuels and industrial products, but some microbes’ metabolisms get in the way, degrading or blocking synthesis of the products scientists want. By keeping an extreme heat-loving microorganism below its accustomed temperature, University of Georgia biochemist Michael Adams and colleagues deactivated many of the hyperthermophile’s own metabolic processes and engineered a pathway that could ultimately be manipulated to produce liquid fuel.  

The methods
Adams and colleagues took five genes from one archaeon (Metallosphaera sedula) that uses hydrogen gas as an energy source to incorporate carbon dioxide into organic compounds, and inserted those genes into the hyperthermophile Pyrococcus furiosus, another archaeon. The modified microbe produced 3-hydoxypropionic acid, a valued industrial compound used in acrylic plastics production.

The innovation
The hyperthermophile P. furiosus grows best at 100 °C, but the scientists cultured it near 70 °C, a temperature at which “it’s sort of a close-to-inactive bowl of cytoplasm, whereas the genes we engineered into it are maximally active at 70 degrees,” says Adams. By shifting the culturing temperature, the team enabled the engineered microbe to efficiently perform new tasks without interference from its usual metabolic processes.

The model
“This is exciting work that extends frontiers in several important ways,” demonstrating both a new way to make useful organic chemicals and a strategy for genetically engineering a heat-loving microbe, says Lee Lynd, a metabolic engineer at Dartmouth College.

Correction (September 9): This story has been updated from its original version to refer to Pyrococcus furiosus and Metallosphaera sedula as archaea, not archaebacteria. The Scientist regrets the error.