On-chip Screening of Chemically Induced Mutant Strains and Assay of Their Metabolites by Liquid Chromatography Tandem Mass Spectrometry

Abstract

The increase of antimicrobial resistance and the outbreak of new diseases have brought unprecedented challenges with antibiotic therapy, and discovering and developing effective compounds to fight against infections or diseases have become a challenge. Conventionally, natural antibiotics or active compounds can be obtained from microorganisms with a long time span, complex screening, and cumbersome operations. In this work, we developed a droplet-based microfluidic platform combined with liquid chromatography tandem mass spectrometry for rapid screening of chemically induced mutant strains and analyzing their metabolites. Using this microfluidic method, N-methyl-N-nitro-N-nitrosoguanidine-induced mutants of two Streptomyces strains, two Salinicoccus strains, a Halomonas strain, and a Planomicrobium strain were screened, and their metabolites were analyzed. Multivariate and heatmap analysis showed that the mutant strains screened by the microfluidic method and traditional method (flasks and agar plates) were clustered and separated evidently from the wild-type strains. The top 20 differential characteristic peaks of all samples were annotated with the HMDB database, and the significant differences of the characteristic peaks indicated that the mutant strains screened by the microfluidic method and traditional method had highly similar metabolic compositions. Results demonstrated that this microfluidic screening method was suitable not only for actinomycete mutant screening, but also for bacterial mutant screening with wide applicability and reliability. Furthermore, this method can reduce screening timescales and simplify cumbersome operations compared with the traditional screening method.