Identification and Characterization of Bacterial Metabolites by Atmospheric Solids Analysis ProbeIon Mobility-Mass Spectrometry (ASAP-IM-MS)
Horness, Rachel E.
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The increasing need for rapid, accurate methods for bacterial identification and characterization arises from a wide range of applications including medical diagnostics, food safety, and chemical/biological warfare agent detection. However, sample preparation and purification are time-consuming, labor intensive, delay potentially time-sensitive results, and often introduce experimental error. Use of the atmospheric solids analysis probe (ASAP) (Waters Corporation, Manchester, UK) in conjunction with ion mobility-mass spectrometry (IM-MS) eliminates several of the limitations associated with current methods of bacterial analysis. ASAP-IM-MS requires little or no sample preparation and utilizes a simple and rapid procedure for detection of volatile and semi-volatile liquid and solid compounds. In addition, IM-MS allows for two-dimensional separation of complex mixtures based on structural variability and mass-to-charge ratios, respectively. In this work ASAP-IM-MS parameters were optimized with solutions of standard metabolites. After initial optimization, several mixtures of standards were prepared to assess the efficacy of metabolite detection in complex solutions. Finally, raw samples of E. coli extracts were analyzed and several identifications of metabolites were made from the unpurified mixture through comparison with metabolite databases. The results reveal that optimized ASAP-IM-MS parameters are heavily dependent upon the identity of the analytes; however, individual metabolites can be identified even within complex mixtures with little sample preparation. Further tailoring of the method for analysis of bacterial extracts will allow for high throughput metabolomic classification of known and newly discovered bacterial strains directly from complex mixtures.