Genome editing of using CRISPR/Cas9

background: Impactful greenhouse gas emissions abatement can now be achieved through gas fermentation using acetogenic microbes for the production of low-carbon fuels and chemicals. However, compared to traditional hosts like or yeast, only basic genetic tools exist for gas-fermenting acetogens. To advance the process, a robust genetic engineering platform for acetogens is essential. results: In this study, we report scarless genome editing of an industrially used model acetogen, , using the CRISPR/Cas9 system. Initial efforts to retrofit the CRISPR/Cas9 system for resulted in poor efficiency likely due to uncontrolled expression of Cas9. To address this, we constructed and screened a small library of tetracycline-inducible promoters that can also be used to fine-tune gene expression. With a new inducible promoter, the efficiency of CRISPR/Cas9-mediated desired gene deletion in was improved to over 50 %, making it a viable tool for engineering . conclusions: Addition of both an inducible promoter library and a scarless genome editing tool is an important expansion to the genetic tool box of industrial strain.