Application of MALDI-TOF to bacteria

As noted above, whole-cell MALDI-TOF MS was intended for rapid taxonomic identification of bacteria. Neither the analysis of specific targeted bacterial proteins, nor the discovery of new proteins, was envisioned as a routine application for which whole cells would be used. An unknown or target protein might not have the abundance or proton affinity to facilitate its detection from such a complex mixture containing literally thousands of other proteins. Thus, for many applications, the analysis of proteins from chromatographically separated fractions remains a more productive approach. From a historical perspective, whole-cell MALDI is a logical extension of MALDI analysis of isolated cellular proteins. After all, purified proteins can be obtained from bacteria after different levels of purification. Differences in method often reflect how much purification is done prior to analysis. With whole-cell MALDI the answer is literally none. Some methods attempt to combine the benefits of the rapid whole cell approach with a minimal level of sample preparation, often based on the analysis of crude fractions rather... 

To date, the vast majority of applications of intact cell MALDI-TOF analyses have been to bacteria. However, preliminary extensions of the approaches used in bacteria have been applied to fungi. From the standpoint of the discovery of novel chemotypes via natural products, this is obviously a desirable step, but it is also clearly in its infancy. Two groups reported [36,37] the observation of relatively simple mass spectral fingerprints from the intact fungal tissue they analyzed. This application might have the advantage of simplified spectral comparisons, relative to those for bacteria, but also means that such comparisons would have fewer data points to support them. 

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