Engineering Corynebacterium glutamicum with a comprehensive genomic library and phage-based vectors

Abstract

The Gram-positive bacterium Corynebacterium glutamicum sustains the industrial production of chiral molecules such as L-amino acids. Through heterologous gene expression, C. glutamicum is becoming a sustainable source of small organic molecules and added-value chemicals. The current methods to implement heterologous genes in C. glutamicum rely on replicative vectors requiring lasting selection or chromosomal integration using homologous recombination. Here, we present a set of dedicated and transversal tools for genome editing and gene delivery into C. glutamicum. We generated a cosmid-based library suitable for efficient double allelic exchange, covering more than 94% of the chromosome with an average 5.1x coverage. We employed the library and an iterative marker excision system to generate the carotenoid-free C. glutamicumBT1-C31-Albino (BCA) host, featuring the attachment sites for actinophages ϕC31 and ϕBT1 for one-step chromosomal integration. As a proof-of-principle, we employed a ϕC31-based integration and a Cre system for the markerless expression of the type III polyketide synthase RppA, and a ϕBT1-based integration system for the expression of the phosphopantetheinylation-dependent non-ribosomal peptide synthetase BpsA in the C. glutamicum BCA host. The developed genomic library and microbial host, and the characterized molecular tools will contribute to the study of the physiology and the rise of C. glutamicum as a leading host for drug discovery.

Keywords: Actinobacteria; Genome editing; Heterologous expression; Natural products.