Rapid Identification of Intact Whole Bacteria Based on Spectral Patterns using Matrix-assisted Laser Desorption/Ionization with Time-of-flight Mass Spectrometry

Abstract

Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was investigated as a method for the rapid identification of whole bacteria, either by comparison with archived reference spectra or by co-analysis with cultures of known bacteria. Bacteria were sampled from colonies on an agar plate, mixed with the matrix, air-dried, and introduced in batches into the mass spectrometer for analysis. In the first experiment, both bacterial strains that had been previously analyzed to obtain reference spectra and other strains that had not been analyzed were blind-numbered and their spectra were obtained. Those strains that matched reference spectra were found to be correctly identified. A second experiment involved co-analysis of reference strains and bind-numbered strains under identical conditions; species-specific identification was demonstrated by comparison of spectra of the blind-numbered strains with those of the standards. In all of the spectra obtained in these experiments, each bacterial strain showed a few characteristic high-mass ions which are thought to be derived from bacterial proteins. This work represents the first reported instance of successful bacterial chemotaxonomy by MALDI-TOFMS analysis of whole cells. For the strains tested, the method is rapid and simple.

Recent and the Latest Developments in Rapid and Efficient Detection of Salmonella in Food and Water

“…Mass spectrometry is an analytical technique, in which individual molecules of a sample can be converted to ions, and the ions are moved about and manipulated by external electric and magnetic fields for detection and identification of pathogens [87][88][89]. The latest types of MS include electrospray ionization (ESI), matrix-associated laser desorption ionization (MALDI), matrix-associated laser desorption ionization-time of flight (MALDI-TOF).…”

The role of gut microbiota in the gut-brain axis: current challenges and perspectives

“…The taxonomic resolution of MALDI-TOF MS is currently considered as a comparable or superior method to comparative 16S rRNA gene sequence analysis. It is recognized that the MS of different bacterial species were distinct from one another, exhibiting the potential of becoming a species discriminating characteristic, analogous to genetic fi nger printing techniques such as amplified fragment length polymorphism (AFLP) or random amplifi cation of polymorphic DNA (RAPD) (Holland et al, 1996;Welker, 2012). Use of this approach in conjunction with ongoing genomic data will greatly facilitate the recognition of gut microbiota composition.…”

“…This included 174 species never described in the human gut (Lagier et al, 2012). However, most of these procedures have so far not exceeded proof-of-principle level and were applied only to a limited number of bacterial species (Holland et al, 1996;Chong et al, 1997). In addition, these procedures do not have proven maturity for easy and systematic application in microbiology.…”

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“…This encouraging study was not followed by any other development until 1996. At this time, the first matrix-assisted laser desorption/ionization time-of-flight MS (MALDI-TOF MS) experiment was successful in identifying bacteria directly from whole colonies based on protein content [4,5] . However, the most important evolution corresponded to the system of detection by soft ionization techniques such as MALDI and electrospray ionization (ESI) allowing the analysis of biomolecules and large organic molecules, which tend to be fragile when ionized by the old other conventional ionization methods [6] .…”