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Applied and Environmental Microbiology, February 2004, p. 883-890, Vol. 70, No. 2
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.2.883-890.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Electrotransformation of Clostridium thermocellum

Michael V. Tyurin,1 Sunil G. Desai,1 and Lee R. Lynd1,2*

Thayer School of Engineering,1 Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 037552

Received 10 September 2003/ Accepted 7 November 2003

Electrotransformation of several strains of Clostridium thermocellum was achieved using plasmid pIKm1 with selection based on resistance to erythromycin and lincomycin. A custom-built pulse generator was used to apply a square 10-ms pulse to an electrotransformation cuvette consisting of a modified centrifuge tube. Transformation was verified by recovery of the shuttle plasmid pIKm1 from presumptive transformants of C. thermocellum with subsequent PCR specific to the mls gene on the plasmid, as well as by retransformation of Escherichia coli. Optimization carried out with strain DSM 1313 increased transformation efficiencies from <1 to (2.2 ± 0.5) x 105 transformants per µg of plasmid DNA. Factors conducive to achieving high transformation efficiencies included optimized periods of incubation both before and after electric pulse application, chilling during cell collection and washing, subculture in the presence of isoniacin prior to electric pulse application, a custom-built cuvette embedded in an ice block during pulse application, use of a high (25-kV/cm) field strength, and induction of the mls gene before plating the cells on selective medium. The protocol and preferred conditions developed for strain DSM 1313 resulted in transformation efficiencies of (5.0 ± 1.8) x 104 transformants per µg of plasmid DNA for strain ATCC 27405 and ~1 x 103 transformants per µg of plasmid DNA for strains DSM 4150 and 7072. Cell viability under optimal conditions was ~50% of that of controls not exposed to an electrical pulse. Dam methylation had a beneficial but modest (7-fold for strain ATCC 27405; 40-fold for strain DSM 1313) effect on transformation efficiency. The effect of isoniacin was also strain specific. The results reported here provide for the first time a gene transfer method functional in C. thermocellum that is suitable for molecular manipulations involving either the introduction of genes associated with foreign gene products or knockout of native genes.

* Corresponding author. Mailing address: Thayer School of Engineering, 8000 Cummings Hall, Rm. 128, Dartmouth College, Hanover, NH 03755. Phone: (603) 646-2231. Fax: (603) 646-2277. E-mail: lee.lynd{at}dartmouth.edu.

Applied and Environmental Microbiology, February 2004, p. 883-890, Vol. 70, No. 2
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.2.883-890.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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  • Tyurin, M. V., Sullivan, C. R., Lynd, L. R. (2005). Role of Spontaneous Current Oscillations during High-Efficiency Electrotransformation of Thermophilic Anaerobes. Appl. Environ. Microbiol. 71: 8069-8076 [Abstract] [Full Text]  
  • Demain, A. L., Newcomb, M., Wu, J. H. D. (2005). Cellulase, Clostridia, and Ethanol. Microbiol. Mol. Biol. Rev. 69: 124-154 [Abstract] [Full Text]  


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