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Surface analysis of bacteria

The surface chemical composition of bacterial cells can be analyzed using several different methods. We have worked to further develop a state-of-the-art ultra-high vacuum method called X-ray photoelectron spectroscopy (XPS) for use on intact bacterial cells (i.e not freeze dried or dehydrated). This work involved analyzing fast-frozen bacteria at liquid nitrogen temperatures. Thereafter we made us of the carbon spectrum and multivariate curve resolution to predict the chemical composition of lipid, polysaccharide and peptide (protein + peptidoglycan) in the outermost part of the intact bacterial cell wall. We have used this method to follow compositional alterations in the cell wall of both Gram-negative and Gram-positive bacteria. We have followed adaptations arising as a result of mutations as well as after exposure to different environmental conditions.

Recently, together with collaborators at Empa in Switzerland, we have started similar method development for bacterial cell wall analysis using time-of-flight secondary ion mass spectrometry (ToF-SIMS).

This work has been funded through grants from Umeå Center for Microbial Research, the Kempe Foundation as well as a visiting resarcher grant from the Swiss National Science Foundation.

Publications of interest:

2011, Monitoring Surface Chemical Changes in the Bacterial Cell Wall – Multivariate analysis of X-ray photoelectron spectroscopy data

2014, The cell wall composition of Bacillus subtilis changes as a function of pH and Zn2+ exposure – insights from cryo-XPS measurements

2016, Analysis of bacterial cell surface chemical composition using cryogenic X-ray photoelectron spectroscopy, Book chapter in Methods in Molecular Biology

2017, Cryo-XPS: probing intact interfaces in nature and life, perspective article

2019, Bacterial Surfaces in Geochemistry - How Can X-ray Photoelectron Spectroscopy Help?