Translating Bacterial Metabolic Exchange with Imaging Mass Spectrometry
Wed 2:30 PM - Track 1: New Advances
Pieter C. Dorrestein
University of California, San Diego
Yu-Liang Yang 1,5, Yuquan Xu 1,5, Paul Straight 4, Pieter C. Dorrestein 1,2,3

1) Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego.
2) Departments of Pharmacology, Chemistry and Biochemistry, University of California, San Diego.
3) Center for Marine Biotechnology and Biomedicine, University of California, San Diego.
4) Department of Biochemistry and Biophysics, Texas A&M University, College Station.
5) The authors contributed equally to this work.
Metabolic exchange is a universal phenomenon that involves exchange of signals that take many chemical forms. Bacterial, archeal, and eukaryal cells produce and respond to numerous different signals. Yet despite the universality of metabolic exchange, there are no tools available to study events involving multiple signals in a spatial fashion. Here we develop and use thin-layer agar natural product MALDI-TOF imaging mass spectrometry (TLA-MALDI-IMS) of intact bacterial colonies grown on top of the MALDI target plate. This approach enables visualization of many natural products from bacteria in culture.

The chemical complexity of microbial metabolic interactions, usually depicted as interspecies chemical warfare, is often inferred. TLA-MALDI-IMS captures complex molecular output by an organism and resolves metabolite production both temporally and spatially during colony growth. We developed the TLA-MALDI-IMS approach by observing several known signals from a growing colony of the Bacillus subtilis and by visualizing interspecies metabolic communication between B. subtilis and Streptomyces coelicolor. Amidst all the signals observed from B. subtilis are surfactin, plipastatin, subtilosin, extracellular polyglutamate, the sporulation killing factor. These signals were tracked and correlated with landmark events of colony development and sporulation. Using mixed-species cultures of B. subtilis and S. coelicolor, TLA-MALDI-IMS provided direct evidence that bacillaene and surfacin, natural products from B. subtilis, silence the defensive metabolic arsenal of S. coelicolor.

Finally we highlight how these approaches are being employed to discover anti-infective paradigms. These results establish the efficacy of TLA-MALDI-IMS as a gateway tool to improve our understanding of multifactorial interspecies signaling.
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