Genome assembly using Nanopore-guided long and error-free DNA reads.
BACKGROUND
Long-read sequencing technologies were launched a few years ago, and in contrast with short-read sequencing technologies, they offered a promise of solving assembly problems for large and complex genomes. Moreover by providing long-range information, it could also solve haplotype phasing. However, existing long-read technologies still have several limitations that complicate their use for most research laboratories, as well as in large and/or complex genome projects. In 2014, Oxford Nanopore released the MinION® device, a small and low-cost single-molecule nanopore sequencer, which offers the possibility of sequencing long DNA fragments.


RESULTS
The assembly of long reads generated using the Oxford Nanopore MinION® instrument is challenging as existing assemblers were not implemented to deal with long reads exhibiting close to 30% of errors. Here, we presented a hybrid approach developed to take advantage of data generated using MinION® device. We sequenced a well-known bacterium, Acinetobacter baylyi ADP1 and applied our method to obtain a highly contiguous (one single contig) and accurate genome assembly even in repetitive regions, in contrast to an Illumina-only assembly. Our hybrid strategy was able to generate NaS (Nanopore Synthetic-long) reads up to 60 kb that aligned entirely and with no error to the reference genome and that spanned highly conserved repetitive regions. The average accuracy of NaS reads reached 99.99% without losing the initial size of the input MinION® reads.


CONCLUSIONS
We described NaS tool, a hybrid approach allowing the sequencing of microbial genomes using the MinION® device. Our method, based ideally on 20x and 50x of NaS and Illumina reads respectively, provides an efficient and cost-effective way of sequencing microbial or small eukaryotic genomes in a very short time even in small facilities. Moreover, we demonstrated that although the Oxford Nanopore technology is a relatively new sequencing technology, currently with a high error rate, it is already useful in the generation of high-quality genome assemblies.
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. amadoui@genoscope.cns.fr.
Mohammed-Amin
MA
Madoui
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. sengelen@genoscope.cns.fr.
Stefan
S
Engelen
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. cruaud@genoscope.cns.fr.
Corinne
C
Cruaud
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. cbelser@genoscope.cns.fr.
Caroline
C
Belser
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. lbertran@genoscope.cns.fr.
Laurie
L
Bertrand
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. aalberti@genoscope.cns.fr.
Adriana
A
Alberti
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. alemainque@genoscope.cns.fr.
Arnaud
A
Lemainque
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. pwincker@genoscope.cns.fr.|Université d'Evry Val d'Essonne, UMR 8030, CP5706, 91057, Evry, France. pwincker@genoscope.cns.fr.|Centre National de Recherche Scientifique (CNRS), UMR 8030, CP5706, 91057, Evry, France. pwincker@genoscope.cns.fr.
Patrick
P
Wincker
Commissariat à l'Energie Atomique (CEA), Institut de Génomique (IG), Genoscope, BP5706, 91057, Evry, France. jmaury@genoscope.cns.fr.
Jean-Marc
JM
Aury
D000150:Acinetobacter / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis; D016680:Genome, Bacterial; D059014:High-Throughput Nucleotide Sequencing / Q000295:instrumentation / Q000379:methods*; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA / Q000295:instrumentation / Q000379:methods*
D004269:DNA, Bacterial