CircoTax: a novel circular representation of differentially abundant microbial ranks

Abstract

One of the most relevant applications of NGS-based microbial abundance analysis is the discovery of taxa that appear as differentially represented between ecological niches. In the last years several methods have been proposed to accomplish this task, invariantly reporting the differentially represented taxa at the appropriate taxonomic rank as well as an adjusted p-value and a log2 fold change, representing the confidence on differential call and the amount of variation recorded. This work describes CircoTax, a specialized R ggplot2 plot representing a rank-aware collection of differentially abundant taxa in an intuitive, compact radial form. Specifically, the CircoTax is a circular plot with sectors encoding the taxonomy depth (from phylum to genus) and, departing from the center, a number of radial bars that reach rank-based sectors whose color and transparency are proportional to the log fold change intensity direction and p-value. The visualization of results is graphically appealing and allows to accommodate tens of differentially abundant ranks each with an associated amount of up or down variation so that results are easily intelligible for each differentially represented taxa at a glance. The software is freely available and can be run natively in R or through a dedicated ShinyApp for an interactive usage.