VTAM: A robust pipeline for validating metabarcoding data using controls

A pile of pipelines: An overview of the bioinformatics software for metabarcoding data analyses

Environmental DNA (eDNA) metabarcoding has gained growing attention as a strategy for monitoring biodiversity in ecology. However, taxa identifications produced through metabarcoding require sophisticated processing of high-throughput sequencing data from taxonomically informative DNA barcodes. Various sets of universal and taxon-specific primers have been developed, extending the usability of metabarcoding across archaea, bacteria and eukaryotes. Accordingly, a multitude of metabarcoding data analysis tools and pipelines have also been developed. Often, several developed workflows are designed to process the same amplicon sequencing data, making it somewhat puzzling to choose one among the plethora of existing pipelines. However, each pipeline has its own specific philosophy, strengths and limitations, which should be considered depending on the aims of any specific study, as well as the bioinformatics expertise of the user. In this review, we outline the input data requirements, supported operating systems and particular attributes of thirty-two amplicon processing pipelines with the goal of helping users to select a pipeline for their metabarcoding projects.

mkLTG: a command-line tool for taxonomic assignment of metabarcoding sequences using variable identity thresholds

Metabarcoding is now a widely used method for biodiversity studies. Taxonomic assignment of environmental sequences is one of the key steps of metabarcoding. Assignments based on lowest common ancestor (LCA) method generally rely on fixed arbitrary thresholds, and this is generally not well adapted for assignment of taxonomically diverse groups with variable coverage in reference databases. The mkLTG is a LCA-based method that uses a series of percentage of identity thresholds starting from stringent parameters and decreasing it if necessary. All parameters can be set separately for each percentage of identity threshold, which makes this tool adaptable for different databases, genetic markers and diverse taxonomic groups. The optimization step was included using the COI marker and a comprehensive, non-redundant database. The mkLTG tool is a command-line application with few dependencies that runs in all operating systems, therefore, it is easy to include into complex pipelines. All scripts are freely available including the benchmarking at https://github.com/meglecz/mkLTG .