Turning the screw: engineering extreme pH resistance in Escherichia coli through combinatorial synthetic operons

Abstract

Adoption of microorganisms as platforms for sustainable biobased production requires host cells to be able to withstand harsh industrial conditions, which are usually far from the ones where these organisms are naturally adapted to thrive. However, novel survival mechanisms unearthed by the study of microbiomes from extreme habitats may be exploited to enhance microbial robustness under the strict conditions needed for different applications. In this work, synthetic biology approaches were used to engineer enhanced acidic tolerance in Escherichia coli under extreme conditions through the characterization of a library of twenty-seven unique operons composed of combinatorial assemblies of three novel genes from an extreme environment and three synthetic ribosome binding sites. The results here presented illustrate the efficacy of combining different metagenomic genes for tolerance in truly synthetic genetic operons, as expression of these gene clusters increased hundred-fold the survival percentage of cells exposed to an acidic shock in minimal media at pH 1.9 under aerobic conditions.