Bamboozle: A Bioinformatic Tool for Identification and Quantification of Intraspecific Barcodes.

Evolutionary changes in populations of microbes, such as microalgae, cannot be traced using conventional metabarcoding loci as they lack intraspecific resolution. Consequently, selection and competition processes among strains of the same species cannot be resolved without elaborate isolation, culturing, and genotyping efforts. Bamboozle, a new bioinformatic tool introduced here, scans the entire genome of a species and identifies allele-rich barcodes that enable direct identification of different genetic strains from a population using amplicon sequencing of a single DNA sample. We demonstrate its usefulness by identifying hypervariable barcoding loci (< 500 bp) from genomic data in two microalgal species, the diploid diatom Skeletonema marinoi and the haploid chlorophyte Chlamydomonas reinhardtii. Across the two genomes, four and twenty-two loci, respectively, were identified that could in silico resolve all analysed genotypes. All of the identified loci are within protein-coding genes with various metabolic functions. Single nucleotide polymorphisms (SNPs) provided the most reliable genetic markers, and among 54 strains of S. marinoi, three 500 bp loci contained, on average, 46 SNPs, 103 strain-specific alleles, and displayed 100% heterozygosity. This high level of heterozygosity was identified as a novel opportunity to improve strain quantification and detect false positive artefacts during denoising of amplicon sequences. Finally, we illustrate how metabarcoding of a single genetic locus can be used to track abundances of S. marinoi strains in an artificial selection experiment. As future genomic datasets become available and DNA sequencing technologies develop, Bamboozle has flexible user settings enabling optimal barcodes to be designed for other species and applications.