Comparison of long-read sequencing technologies in the hybrid assembly of complex bacterial genomes

De Maio, Nicola; Shaw, Liam P.; Hubbard, Alasdair; George, Sophie; Sanderson, Nicholas D.; Swann, Jeremy; Wick, Ryan; AbuOun, Manal; Stubberfield, Emma; Hoosdally, Sarah J.; Crook, Derrick W.; Peto, Timothy E.A.; Sheppard, Anna E.; Bailey, Mark J.; Read, Daniel S.; Anjum, Muna F.; Walker, A. Sarah; Stoesser, Nicole. 2019 Comparison of long-read sequencing technologies in the hybrid assembly of complex bacterial genomes. Microbial Genomics, 5 (9), 000294. 12, pp.

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Illumina sequencing allows rapid, cheap and accurate whole genome bacterial analyses, but short reads (<300 bp) do not usually enable complete genome assembly. Long-read sequencing greatly assists with resolving complex bacterial genomes, particularly when combined with short-read Illumina data (hybrid assembly). However, it is not clear how different long-read sequencing methods affect hybrid assembly accuracy. Relative automation of the assembly process is also crucial to facilitating high-throughput complete bacterial genome reconstruction, avoiding multiple bespoke filtering and data manipulation steps. In this study, we compared hybrid assemblies for 20 bacterial isolates, including two reference strains, using Illumina sequencing and long reads from either Oxford Nanopore Technologies (ONT) or SMRT Pacific Biosciences (PacBio) sequencing platforms. We chose isolates from the family Enterobacteriaceae, as these frequently have highly plastic, repetitive genetic structures, and complete genome reconstruction for these species is relevant for a precise understanding of the epidemiology of antimicrobial resistance. We de novo assembled genomes using the hybrid assembler Unicycler and compared different read processing strategies, as well as comparing to long-read-only assembly with Flye followed by short-read polishing with Pilon. Hybrid assembly with either PacBio or ONT reads facilitated high-quality genome reconstruction, and was superior to the long-read assembly and polishing approach evaluated with respect to accuracy and completeness. Combining ONT and Illumina reads fully resolved most genomes without additional manual steps, and at a lower consumables cost per isolate in our setting. Automated hybrid assembly is a powerful tool for complete and accurate bacterial genome assembly.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: Soils and Land Use (Science Area 2017-)
Directors, SCs
ISSN: 2057-5858
Additional Information. Not used in RCUK Gateway to Research.: Open Access paper - full text available via Official URL link.
Additional Keywords: hybrid assembly, bacterial genomics, long-read sequencing, Enterobacteriaceae, plasmid assembly
NORA Subject Terms: Biology and Microbiology
Date made live: 18 Oct 2019 09:15 +0 (UTC)

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