Bioinformatics Advance Access published online on April 23, 2009
Bioinformatics, doi:10.1093/bioinformatics/btp275
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A Practical Algorithm for Finding Maximal Exact Matches in Large Sequence Data Sets Using Sparse Suffix Arrays
Department of Computer Science1, Department of Molecular Biology2, Department of Ecology and Evoluationary Biology3, Lewis-Sigler Institute for Integrative Genomics4, and Howard Hughes Medical Institute5, Princeton University, Princeton, New Jersey 08544, USA
*To whom correspondence should be addressed. Zia Khan and Mona Singh, E-mail: zkhan{at}princeton.edu, zkhan{at}cs.princeton.edu, mona{at}cs.princeton.edu
| Abstract |
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Motivation: High-throughput sequencing technologies place ever increasing demands on existing algorithms for sequence analysis. Algorithms for computing maximal exact matches (MEMs) between sequences appear in two contexts where high-throughput sequencing will vastly increase the volume of sequence data: (1) seeding alignments of high-throughput reads for genome assembly and (2) designating anchor points for genome-genome comparisons.
Results: We introduce a new algorithm for finding MEMs. The algorithm leverages a sparse suffix array, a text index that stores every Kth position of the text. In contrast to a full text index that stores every position of the text, a sparse suffix array occupies much less memory. Even though we use a sparse index, the output of our algorithm is the same as a full text index algorithm as long as the space between the indexed suffixes is not greater than a minimum length of a MEM. By relying on partial matches and additional text scanning between indexed positions, the algorithm trades memory for extra computation. The reduced memory usage makes it possible to determine MEMs between significantly larger sequences.
Availability: Source code for the algorithm is available under a BSD open source license at http://compbio.cs.princeton.edu/mems. The implementation can serve as a drop-in replacement for the MEMs algorithm in MUMmer 3.
Contact: zkhan{at}cs.princeton.edu, mona{at}cs.princeton.edu
Associate Editor: Prof. John Quackenbush
Received on January 28, 2009; revised on March 31, 2009; accepted on April 19, 2009