Bioanalysis Zone

Ambient ESI-MS may present an improved approach to metabolite screening


ESI flow-probe has been demonstrated in achieving real-time metabolomics on living microorganisms.

Scientists have reported on the application of real-time MS in order to quickly screen microbial metabolic output in an attempt to discover novel and invaluable compounds for agriculture, biological research and drug discovery.

“As chemists screen through large numbers of microbial colonies to find new compounds, they need to be able to take quick snapshots of a colony’s molecular profile,” explains Pieter Dorrestein, leader of the research project and a bioanalytical mass spectrometrist at the University of California (CA, USA).

Current analytical methods for this purpose generally entail either putting the microbes in a vacuum chamber, thereby killing the microbes, or collecting the compounds and separating them before identification, a typically time-consuming process.

In the report, Dorrestein and co-workers describe the utilization of a liquid microjunction surface sampling probe for ESI-MS to extract and ionize metabolite mixtures directly from living microbial colonies, which were grown on soft nutrient agar in Petridishes, without any sample pretreatment. According to Dorrestein, using this technique, the solvent flow is at such a rate that the microbes are left intact.

To validate the method, the team applied the approach to more than 30 microorganisms, and were able to confirm the presence of metabolites known to be secreted by the selected strains.

Jonathan Trinidad, a biological mass spectrometrist at Indiana University (IN, USA), who was not involved in the study, commented that the study provides a good demonstration that this probe can capture data from a broad range of organisms. Trinidad added that, “As with other approaches, there is still room to improve the method’s sensitivity, robustness and ease of use.”

Source: Hsu C, ElNaggar MS, Peng Y et al. Real-time metabolomics on living microorganisms using ambient electrospray ionization flow-probe. Anal. Chem. doi:10.1021/ac401613x (2013) (Epub ahead of print).



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