MALDI imaging of microbial colonies on agar media is a growing application for mass spectrometry imaging; however, matrix deposition on agar is often complicated. Typically, matrix is applied to wet agar using a fine sieve to dust matrix powder over the top of the slide, which often yields low to medium signal intensity and poor reproducibility. Using the HTX TM-Sprayer to deposit matrix on microbial colonies prior to mass spectrometry imaging allows for easier and more reproducible matrix application.

HTX Application Note #36 Homogenous Spray Application of DHB on Dried Agar for MALDI Imaging of Microbial Cultures

We present a workflow for applying 2,5-dihydroxybenzoic acid (DHB) to dried agar slices for MALDI imaging of metabolites from bacterial colonies. The MALDI mass spectra acquired in the agar and the bacterial colony when matrix was applied using the HTX TM-Sprayer contained many more peaks than the spectra acquired when the matrix was applied via dry coating with a sieve.

HTX Application Note #40 - Re-discovering Bacterial Biofilm Heterogeneity with MALDI MSI

The combination of MALDI MSI, LA-ICP IMS and proteomics provides a powerful tool for the study of protein profiles (i.e. identification and spatial localization) and metal homeostasis within a bacterial biofilm, granting us the opportunity to rediscover biofilm architecture and heterogeneity, which seems tightly correlated with patterns of nutrient availability.