MicrobeMod: A computational toolkit for identifying prokaryotic methylation and restriction-modification with nanopore sequencing

Abstract

Bacteria and archaea use restriction-modification (R-M) systems to distinguish self from foreign DNA by methylating their genomes with DNA methyltransferases with diverse sequence specificities, and these immunity systems often vary at the strain level. Identifying active methylation patterns and R-M systems can reveal barriers to the introduction of recombinant DNA or phage infection. Here, we present the computational MicrobeMod toolkit for identifying 5mC and 6mA methylation sequence motifs and R-M systems in bacterial genomes using nanopore sequencing of native DNA. We benchmark this approach on a set of reference E. coli strains expressing methyltransferases with known specificities. We then applied these analyses to 31 diverse bacterial and archaeal organisms to reveal the methylation patterns of strains with previously unexplored epigenetics, finding that prokaryotic 5-methylcytosine may be more common than previously reported. In summary, MicrobeMod can rapidly reveal new epigenetics within a prokaryotic genome sequenced with Oxford Nanopore R10.4.1 flow cells at sequencing depths as low as 10x and only requires native DNA. This toolkit can be used to advance fundamental knowledge of bacterial methylation and guide strategies to overcome R-M barriers of genetic tractability in non-model microbes.