AmpliconHunter: A Scalable Tool for PCR Amplicon Prediction from Microbiome Samples

Sequencing of PCR amplicons generated using degenerate primers (typically targeting a region of the 16S ribosomal gene) is widely used in metagenomics to profile the taxonomic composition of complex microbial samples. To reduce taxonomic biases in primer selection it is important to conduct in silico PCR analyses of the primers against large collections of up to millions of bacterial genomes. However, existing in silico PCR tools have impractical running time for analyses of this scale. In this paper we introduce AmpliconHunter, a highly scalable in silico PCR package distributed as an open-source command-line tool and publicly available through a user-friendly web interface at https://ah1.engr.uconn.edu/. AmpliconHunter implements an accurate nearest-neighbor model for melting temperature calculations, allowing for primer-template hybridization with mismatches, along with three complementary methods for estimating off-target amplification. By taking advantage of multi-core parallelism and SIMD operations available on modern CPUs, the AmpliconHunter web server can complete in silico PCR analyses of commonly used degenerate primer pairs against the 2.4M genomes in the latest AllTheBacteria collection in as few as 6–7 h.