Restarting a Microbial Genome After its Modification in Yeast

The Science

Many microbes grow extremely slowly in their native environments, and because of this have been difficult to adapt for DOE missions through genetic engineering. A team at the Venter Institute has developed a solution to this difficult problem. They have shown previously that a small bacterial genome can be transferred into a much larger yeast host and maintained therein. The bacterial genome can then be modified by methods that are routine in the yeast host. The new development demonstrates that the engineered genome can be transferred back into a
bacterial shell with intact function. This success opens a pathway for modifying the genomes of many bacteria that could be valuable for addressing bioenergy and environmental missions.

Summary

When engineering bacteria, it can be advantageous to propagate the genomes in yeast. However, to be truly useful, one must be able to transplant the bacterial chromosome from yeast back into a recipient bacterial cell. But because yeast does not contain restriction-modification systems, such transplantation poses problems not encountered in transplantation from one bacterial cell to another. Bacterial genomes isolated after growth in yeast are likely to be susceptible to the restriction-modification system(s) of the recipient cell, as well as their own. These researchers describe multiple steps, including in vitro DNA methylation, developed to overcome such barriers. A Mycoplasma mycoides large-colony genome was propagated in yeast as a centromeric plasmid, engineered via yeast genetic systems, and, after specific methylation, transplanted into M. capricolum to produce a bacterial cell with the genotype and phenotype of the altered M. mycoides large-colony genome.

BER Program Manager

Dawn Adin

U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]

References

Lartigue, C., S. Vanshee, M. A. Algire, R.-Y. Chuang, G. A. Benders, L. Ma, V. N. Noskov, E. A. Denisova, D. G. Gibson, N. Assad-Garcia, N. Alperovich, D. W. Thomas, C. Merryman, C. A Hutchison III, H. O. Smith, J. C. Venter, and J. I. Glass. 2009. “Creating Bacterial Strains from Genomes That Have Been Cloned and Engineered in Yeast,” Science 325, 1693–96. DOI:10.1126/science.1173759.