Freeze-Dried-Conserved Bacteria Can Be Identified by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Without the Need of Prior Culturing

Abstract

Introduction:

Biobanking practices are continuously evolving to improve and accelerate sample preparation and analysis.

Objectives:

At the Biological Resource Center of the Institut Pasteur, our goal is to develop new and optimized methods for sample processing. In this study, we aimed to establish a culture-independent approach for identifying bacteria directly from their freeze-dried state.

Methods:

Freeze-dried bacteria from 25 species were reconstituted in saline solution, mechanically lysed, and their proteins extracted with acetonitrile and formic acid, followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis.

Results:

The method enabled the reliable identification of diverse bacterial species. Spectrophotometric measurements led to the definition of a reproducible O.D.₆₀₀ threshold, above which all strains were consistently and accurately identified.

Conclusion:

This approach provides a fast and robust alternative for the characterization of bacterial samples across diverse taxonomic groups.