Imaging Metabolites in Agar‐Based Bacterial Co‐Cultures with Minimal Sample Preparation using a DIUTHAME Membrane in Surface‐Assisted Laser Desorption/Ionization Mass Spectrometry**

Abstract

AbstractWhile the imaging of bacteria, directly on agar‐based media, has been reported in matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI), such samples usually require laborious and time‐consuming preparation prior to analysis. Furthermore, the MALDI sample preparation may require desiccation, potentially causing sample deformation and/or degradation. Other issues may be associated with the use of a matrix in MALDI‐MSI. Here, we propose an alternative approach to image a co‐culture of Pseudomonas and Bacillus bacteria, grown on agar, in the positive and negative ionization modes, using surface‐assisted laser desorption/ionization (SALDI) MSI. A rapid and easy sample preparation was performed using a “desorption/ionization using through‐hole alumina membrane” (DIUTHAME) with a blotting method. The porous DIUTHAME membrane was used (1) for the transfer of the metabolites from the sample to the membrane, and (2) as assisting material in SALDI‐MSI. The advantages and limitations of this new sample preparation are discussed in this paper.