Impact of CRISPR interference on strain development in biotechnology.

Genetic perturbation systems are of great interest to redirect metabolic fluxes for value-added production, as well as genetic screening for the development of new drugs, or to identify new targets for biotechnological applications. Here, we review CRISPR interference (CRISPRi), a method for gene expression using a catalytically inactive version of the CRISPR-associated protein 9 (dCas9) of the widely applied CRISPR-Cas9 genome editing system. In combination with the appropriate sgRNA, dCas9 binds to specific DNA sequences without causing double-stranded DNA breakage but interfering with transcription initiation or elongation. Besides manifold uses to interrogate the physiology of a bacterial cell, CRISPRi is used in applications for metabolic engineering and strain development in industrial biotechnology. Albeit in its infancy, CRISPRi has already delivered the first success stories; however, we also analyze limitations of the CRISPRi system and give future perspectives.