A transferrable and integrative type I-F Cascade for heterologous genome editing and transcription modulation
The Class 1 type I CRISPR-Cas systems represent the most abundant and diverse CRISPR systems in nature. However, their applications for generic genome editing have been hindered by difficulties of introducing the class-specific, multi-component effectors in heterologous hosts for functioning. Here we established a transferrable Cascade system that enables stable integration and expression of a complete and highly active I-F Cascade in the notoriously recalcitrant and diverse P. aeruginosa genomes by conjugation. The transferred Cascade displayed substantially higher DNA interference activity and greater editing capacity than the Cas9 system in diverse genetic backgrounds, including removal of the large (21-kb) integrated cassette with efficiency and simplicity. An advanced {lambda}red-I-F system enabled editing in genotypes with poor homologous recombination capacity, clinical isolates lacking sequence information, and cells containing anti-CRISPR elements Acrs. Lastly, an all-in-one I-F Cascade-mediated CRISPRi platform was developed for transcription modulation by simultaneous introduction of the Cascade and the mini-CRISPR array expressing desired crRNA in one-step. This study provides a framework for expanding the diverse type I Cascades for widespread, heterologous genome editing and establishment of editing techniques in non-model isolates of pathogens.