Complete reference genome assemblies and annotations of three Escherichia coli MRE162 clones

ABSTRACT Escherichia coli MRE162 was originally isolated from a toilet pan in 1949 and since been utilized in numerous studies. Here, we sequence, assemble, and annotate clones held at three laboratories providing reference-level assemblies. We show the uniqueness of MRE162 to strains in open databases and make the UK clone publically available.

in 1949, freeze-dried in a glass ampoule in 1967, and stored at −20°C.The strain has been characterized in depth regarding aerosol survival and "Open Air Factor" interaction (1)(2)(3)(4)(5)(6).The original clone was gifted to DGA, France, in 2002 and FFI, Norway, in 2014 for separate studies at these laboratories.We now retrospectively check for mutations between the three clones, which could potentially impact comparisons between studies.
The reads were assembled to complete circularized chromosomes and plasmids.Chromosome and plasmid length were comparable (Fig. 1 and Table 1) between the three clones, except for A 5.1 kb deletion noted in the FRA clone chromosome.
Comparing chromosomes and plasmids at the nucleotide level shows >99.9% identity between clones compared to 96.6% identity to the closest identified E. coli chromosome (strain S30: CP010231) and 82.39% identity to the closest plasmid (strain S30: CP010234).Highlighting the uniqueness of the MRE162 plasmid, only 45.18% of its length aligned with the S30 plasmid.These genome assemblies and annotations, alongside the publicly available culture, provide invaluable data for future evolutionary and functional studies.

ACKNOWLEDGMENTS
We wish to thank Gunnar Skogan and Tone Aarskaug for culturing and DNA isolation of the Norwegian MRE162 clone, Mathieu Giraud for the French clone, and Matthew Bird for the UK clone.We also thank Pascal Rameil and Jerôme Chatoux for the sequencing of the French clone.We acknowledge microbes NG for DNA isolation and sequencing (Illumina and Nanopore) of the UK clone.

TABLE 1
Assembly statistics, sequence data and genome annotation a Statistics from Bowtie2 and Minimap2 for both the chromosome and plasmid of the three MRE162 clones.Annotation for each complete genome from PGAP.