Characterisation of intact microorganisms using electrospray ionisation mass spectrometry

We report the first application of electrospray ionisation mass spectrometr y (ESI-MS) for the reproducible characterisation of strains of intact Gram- negative and Gram-positive bacteria. Electrospray ionisation was performed in both the positive and negative ion modes and the spectra obtained from E scherichia coli and Bacillus cereus were very information rich. Several of the observed negative mass ion fragments from E. coli could be assigned to specific fragmentation from bacterial phospholipids. Cluster analyses of th ese spectra showed that ESI-MS could be used to discriminate between these microorganisms to below species level. Therefore we conclude that ESI-MS co nstitutes a powerful approach to the characterisation and speciation of int act microorganisms. (C) 1999 Federation of European Microbiological Societi es. Published by Elsevier Science B.V. All rights reserved.