SyngenicDNA: stealth-based evasion of restriction-modification barriers during bacterial genetic engineering

Restriction-modification (RM) systems hinder the use of genetic approaches in the vast majority of bacteria. Here, we describe a systematic approach to adapt genetic tools for use in bacteria that are genetically intractable or poorly tractable owing to active RM defenses. In this process, we determine the genome and methylome of a bacterial strain and use this information to define the bacterium9s RM target motifs. We then synonymously eliminate RM targets from the nucleotide sequence of a genetic tool in silico, synthesize an RM-silent 9SyngenicDNA9 tool and propagate the tool as novel minicircle plasmids, termed SyMPL tools, before transformation. Using SyngenicDNA and SyMPL tools, we achieved a profound, u003e100,000-fold, improvement in the transformation of a clinically relevant USA300 strain of Staphylococcus aureus demonstrating the efficacy of these approaches for evading RM systems. The SyngenicDNA and SyMPL approaches are effective, flexible, and should be broadly applicable in microbial genetics. We expect these will facilitate a new era of microbial genetics free of the restraints of restriction-modification barriers.