title: Comparison of single-molecule sequencing and hybrid approaches for finishing the genome of Clostridium autoethanogenum and analysis of CRISPR systems in industrial relevant Clostridia.
abstract: BACKGROUND
  Clostridium autoethanogenum strain JA1-1 (DSM 10061) is an acetogen capable of fermenting CO, CO2 and H2 (e.g. from syngas or waste gases) into biofuel ethanol and commodity chemicals such as 2,3-butanediol. A draft genome sequence consisting of 100 contigs has been published.
  
  
  RESULTS
  A closed, high-quality genome sequence for C. autoethanogenum DSM10061 was generated using only the latest single-molecule DNA sequencing technology and without the need for manual finishing. It is assigned to the most complex genome classification based upon genome features such as repeats, prophage, nine copies of the rRNA gene operons. It has a low G + C content of 31.1%. Illumina, 454, Illumina/454 hybrid assemblies were generated and then compared to the draft and PacBio assemblies using summary statistics, CGAL, QUAST and REAPR bioinformatics tools and comparative genomic approaches. Assemblies based upon shorter read DNA technologies were confounded by the large number repeats and their size, which in the case of the rRNA gene operons were ~5 kb. CRISPR (Clustered Regularly Interspaced Short Paloindromic Repeats) systems among biotechnologically relevant Clostridia were classified and related to plasmid content and prophages. Potential associations between plasmid content and CRISPR systems may have implications for historical industrial scale Acetone-Butanol-Ethanol (ABE) fermentation failures and future large scale bacterial fermentations. While C. autoethanogenum contains an active CRISPR system, no such system is present in the closely related Clostridium ljungdahlii DSM 13528. A common prophage inserted into the Arg-tRNA shared between the strains suggests a common ancestor. However, C. ljungdahlii contains several additional putative prophages and it has more than double the amount of prophage DNA compared to C. autoethanogenum. Other differences include important metabolic genes for central metabolism (as an additional hydrogenase and the absence of a phophoenolpyruvate synthase) and substrate utilization pathway (mannose and aromatics utilization) that might explain phenotypic differences between C. autoethanogenum and C. ljungdahlii.
  
  
  CONCLUSIONS
  Single molecule sequencing will be increasingly used to produce finished microbial genomes. The complete genome will facilitate comparative genomics and functional genomics and support future comparisons between Clostridia and studies that examine the evolution of plasmids, bacteriophage and CRISPR systems.
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.|BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.|Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996, USA.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Brown
authors.affiliation: LanzaTech NZ, Ltd., Auckland, New Zealand.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Nagaraju
authors.affiliation: Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996, USA.
authors.forename: Sagar
authors.initials: S
authors.lastname: Utturkar
authors.affiliation: LanzaTech NZ, Ltd., Auckland, New Zealand.
authors.forename: Sashini
authors.initials: S
authors.lastname: De Tissera
authors.affiliation: LanzaTech NZ, Ltd., Auckland, New Zealand.
authors.forename: Simón
authors.initials: S
authors.lastname: Segovia
authors.affiliation: LanzaTech NZ, Ltd., Auckland, New Zealand.
authors.forename: Wayne
authors.initials: W
authors.lastname: Mitchell
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Miriam L
authors.initials: ML
authors.lastname: Land
authors.affiliation: LanzaTech NZ, Ltd., Auckland, New Zealand.
authors.forename: Asela
authors.initials: A
authors.lastname: Dassanayake
authors.affiliation: LanzaTech NZ, Ltd., Auckland, New Zealand.
authors.forename: Michael
authors.initials: M
authors.lastname: Köpke