an alternative to the USEARCH tool developed by Robert C. Edgar (2010) for which the source code is not publicly available, VSEARCH is an open source, multithreaded 64-bit tool for processing and preparing metagenomics, genomics, and population genomics nucleotide sequence data. It supports de novo and reference based chimera detection, clustering, full-length and prefix dereplication, rereplication, reverse complementation, masking, all-vs-all pairwise global alignment, exact and global alignment searching, shuffling, subsampling, and sorting. It also supports FASTQ file analysis, filtering, conversion, and merging of paired-end reads.