Frequency-based haplotype reconstruction from deep sequencing data of bacterial populations

Clonal populations accumulate mutations over time, resulting in different haplotypes. Deep sequencing of such a population in principle provides information to reconstruct these haplotypes and the frequency at which the haplotypes occur. However, this reconstruction is technically not trivial, especially not in clonal systems with a relatively low mutation frequency. The low number of segregating sites in those systems adds ambiguity to the haplotype phasing and thus obviates the reconstruction of genome-wide haplotypes based on sequence overlap information.

Therefore, we present EVORhA, a haplotype reconstruction method that complements phasing information in the non-empty read overlap with the frequency estimations of inferred local haplotypes. As was shown with simulated data, as soon as read lengths and/or mutation rates become restrictive for state-of-the-art methods, the use of this additional frequency information allows EVORhA to still reliably reconstruct genome-wide haplotypes. On real data, we show the applicability of the method in reconstructing the population composition of evolved bacterial populations and in decomposing mixed bacterial infections from clinical samples.

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Pulido-Tamayo, Sergio; Sanchez-Rodriguez, Aminael; Swings, Toon; Van den Bergh, Bram; Dubey, Akanksha; Steenackers, Hans; Michiels, Jan; Fostier, Jan; Marchal, Kathleen
NUCLEIC ACIDS RESEARCH, 43 (16):10.1093/nar/gkv478 SEP 18 2015