Accelerating Strain Engineering using Desorption Electrospray Ionization-Imaging Mass Spectrometry and Untargeted Molecular Analysis of Intact Microbial Colonies.

Progress in the fields of genomic and biologic sciences has yielded microbial bioprocesses for the advanced production of chemicals. While biomanufacturing has the potential to address global demands for renewable fuels and chemicals, engineering microbial cell factories that can compete with synthetic chemical processes remains a challenge. Optimizing strains for enhanced chemical production is no longer limited by reading and writing DNA, rather it is impeded by the lack of high-throughput platforms for characterizing the metabolic phenotypes resulting from specific gene editing events. To address this issue, we have developed a desorption electrospray ionization- imaging mass spectrometry (DESI-IMS) screening assay that is conducive to both multiplexed sampling and untargeted analyses. This technology bridges the gap between genomic and metabolomic timescales by simultaneously characterizing the chemical output of various engineered Escherichia coli strains rapidly and directly under ambient conditions. The developed method was used to phenotype four E. coli strains on the basis of measured metabolomes, which were validated via PCR genotyping. Untargeted DESI-IMS phenotyping suggests multiple strategies for future engineering which include: (i) relative amounts of specific biosynthetic products, (ii) identification of secondary products, and (iii) the metabolome of engineered organisms. In sum, we present a workflow to accelerate strain engineering by providing rapid, untargeted, and multiplexed analyses of microbial metabolic phenotypes.