PASS-bis: a bisulfite aligner suitable for whole methylome analysis of Illumina and SOLiD reads

The sequencing of bisulfite-treated DNA (Bi-Seq) is becoming a gold standard for methylation studies. The mapping of Bi-Seq reads is complex and requires special alignment algorithms. This problem is particularly relevant for SOLiD color space, where the bisulfite conversion C/T changes two adjacent colors into 16 possible combinations. Here, we present an algorithm that efficiently aligns Bi-Seq reads obtained either from SOLiD or Illumina. An accompanying methylation-caller program creates a genomic view of methylated and unmethylated Cs on both DNA strands. Availability and implementation: The algorithm has been implemented as an option of the program PASS, freely available at http://pass.cribi.unipd.it.