Long-read reconstruction of many diverse haplotypes with devider

Reconstructing exact haplotypes is important when sequencing a mixture of similar sequences. Long-read sequencing can connect distant alleles to disentangle similar haplotypes, but handling sequencing errors requires specialized techniques. Here, we present <i>devider</i>, an algorithm for haplotyping small sequences, such as viruses or genes, from long-read sequencing. devider uses a positional de Bruijn graph with sequence-to-graph alignment on an alphabet of informative alleles to provide a fast assembly-inspired approach compatible with various long-read sequencing technologies. On a synthetic Oxford Nanopore Technologies (ONT) long-read data set containing seven HIV strains, devider recovers 97% of the haplotype content and has the most accurate abundance estimates while taking <4 min and 1 GB of memory for >8000× coverage. Benchmarking on synthetic mixtures of antimicrobial-resistance (AMR) genes shows that devider recovers 83% of haplotypes, 23 percentage points higher than the next best method. On real Pacific Biosciences (PacBio) and ONT data sets, devider recapitulates previously known results in seconds, disentangling a bacterial community with more than 10 strains and an HIV-1 coinfection data set. We use devider to investigate the within-host diversity of a long-read bovine gut metagenome enriched for AMR genes, discovering 13 distinct haplotypes for a <i>tet(Q)</i> tetracycline-resistance gene with >18,000× coverage and six haplotypes for a <i>CfxA2</i> beta-lactamase gene. We find clear recombination blocks for these AMR gene haplotypes, showcasing devider's ability to unveil evolutionary signals for heterogeneous mixtures.