What is "picrust"

PICRUSt is a bioinformatics software, the name is an abbreviation for phylogenetic investigation of communities by reconstruction of unobserved states. The tool serves in the field of metagenomic analysis where it allows inference of the functional profile of a microbial community based on marker gene survey along one or more samples. In essence, PICRUSt takes a user supplied OTU table, representing the marker gene sequences (most commonly a 16S cluster) accompanied with its relative abundance in each of the samples. The output of PICRUSt is a sample by functional-gene-count marix, telling the count of each functional-gene in each of the samples surveyed. The ability of PICRUSt to estimate the functional-gene profile for a given sample relies on a set of known sequenced genomes. For each of the marker genes in the actual samples, PICRUSt tries to retrieve the phylogenetically closest known sequenced genome(s), and from that derive the approximated functional gene content of the unknown genome represented by the given marker gene.