New Genetic Tools for Engineering a Biomass-Degrading Microbe


Achieving efficient and cost-effective breakdown of cellulosic plant biomass remains a significant barrier to the development of economically competitive biofuels that do not compete with food supplies. The hot spring bacterium Caldicellulosiruptor has been shown to efficiently degrade biomass (e.g., switch grass and corn stover) at temperatures over 160° Fahrenheit, but further characterization and engineering of this organism for biofuel production has proven challenging due to a lack of tools for genetic manipulation. Researchers at the DOE BioEnergy Science Center (BESC) have now developed the first system allowing the stable introduction of foreign DNA elements into this microbe. This breakthrough is based on the identification of a Caldicellulosiruptor “immune system” that normally protects the bacterium from viral infection, destroying outside DNA before it can be integrated into the host genome. The BESC team was able develop a set of targeted nucleic acid modifications that protects DNA from the host immune system and allows the introduction of new genes and regulatory elements into the organism. Now that Caldicellulosiruptor is a step closer to the model status of an easily manipulated microbe like E. coli, the team can more effectively study the organism’s unique cellulose-degrading properties and engineer new metabolic pathways that would allow direct conversion of plant biomass into next-generation biofuels.


Chung, D., J. Farkas, J. R. Huddleston, E. Olivar, and J. Westpheling. 2012. “Methylation by a Unique a-class N4-Cytosine Methyltransferase Is Required for DNA Transformation of Caldicellulosiruptor bescii DSM6725,” PLoS ONE 7(8), e43844. DOI: 10.1371/journal.pone.0043844.