05/05/2013
New Technique for Improved Microbial Genome Assembly
Summary
In addition to sequencing the genomes of microbes, plants, fungi, and metagenomes, the U.S. Department of Energy’s (DOE) Joint Genome Institute (JGI) develops tools to improve the assembly and analysis of the DNA sequences that it generates. One tool, HGAP (Hierarchical Genome Assembly Process), provides a fully automated workflow for users of the Pacific Biosciences’ single molecule, real-time DNA sequencing machine. The “PacBio” sequencer generates initial DNA sequences up to 10 or more times longer than those provided by other technologies, which is a great assistance in the assembly of sequences into more complete genomes, but at a higher cost and lower accuracy. Competing sequencing technologies involve creating multiple DNA libraries, conducting multiple runs, and combining the data. I n contrast, HGAP requires just a single, long-insert, shotgun DNA library, enabling the resolution of long regions of repeated DNA sequence that often complicate other assembly methods. This new assembly method was tested using three microbes previously sequenced by DOE JGI. The HGAP produced final assemblies with >99.999% accuracy when compared to the reference sequences for these microbes. Next steps in the project will focus on extending HGAP’s utility beyond microbes to the larger genomes of more complex organisms. By improving sequence assemblies in this way, sequencing information can more readily be developed into understanding the role of biological processes and genes in DOE bioenergy and environmental missions.
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References
Chin, C.-S., D. H. Alexander, P. Marks, A. K. Klammer, J. Drake, C. Heiner, A. Clum, A. Copeland, J. Huddleston, E. E. Eichler, S. W. Turner, and J. Korlach. 2013. “Nonhybrid, Finished Microbial Genome Assemblies from Long-Read SMRT Sequencing Data,” Nature Methods 10, 563–69. DOI: 10.1038/nmeth.2474.