High-Efficiency Genome Editing Based on Endogenous CRISPR-Cas System Enhances Cell Growth and Lactic Acid Production in Pediococcus acidilactici.

Pediococcus acidilactici is commonly used for pediocin production and lactic acid fermentation. However, a high-efficiency genome editing tool is unavailable for this species. In this study, we constructed endogenous subtype II-A CRISPR-Cas system-based genome interference plasmids which carried a "repeat-spacer-repeat" cassette in the pMG36e shuttle vector. These plasmids exhibited self-interference activities in P. acidilactici LA412. Then, the genome-editing plasmids were constructed by cloning the upstream/downstream donor DNA into the corresponding interference plasmids to exert high-efficiency markerless gene deletion, gene integration, and point mutation in P. acidilactici LA412. We found that endogenous CRISPR-mediated depletion of the native plasmids enhanced the cell growth and that integration of an l-lactate dehydrogenase gene into the chromosome enhanced both cell growth and lactic acid production. IMPORTANCE A rapid and precise genome editing tool will promote the practical application of Pediococcus acidilactici, one type of lactic acid bacterium with excellent stress tolerance and probiotic characteristics. This study established a high-efficiency endogenous CRISPR-Cas system-based genome editing tool for P. acidilactici and achieved different genetic manipulations, including gene deletion, gene insertion, mononucleotide mutation, and endogenous plasmid depletion. The engineered strain edited by this tool showed significant advantages in cell growth and lactic acid fermentation. Therefore, our tool can satisfy the requirements for genetic manipulations of P. acidilactici, thus making it a sophisticated chassis species for synthetic biology and bioindustry.