Development and application of base editors in bacterial genome editing

Abstract:

Base editors are novel genome-editing tools developed in the past two years that comprise fusions between a catalytically disabled CRISPR/Cas endonuclease and a base deaminase to deaminate the exocyclic amine of the target bases, thereby leading to base substitutions in DNA or RNA. Two classes of base editors have been developed, namely DNA base editors and RNA base editors. Two types of DNA editors have been described: cytosine base editors (CBEs) convert C to T and adenine base editors (ABEs) convert A to G. Base editors do not create double-strand DNA breaks (DSBs) and do not rely on cellular non-homologous end joining (NHEJ) and homology-directed repair (HDR), so they minimize the generation of DSB-associated by products, such as small insertions or deletion (indels). RNA base editors based on CRISPR/Cas systems could achieve adenosine conversion to inosine. In this review, we summarize the development process, scope of application and editing features of base editors and highlight their recent applications in bacterial genome editing. Finally, we will also briefly discuss limitations and future directions of base editors for applications in bacteria.