Identification by MALDI-TOF mass spectrometry
MALDI-TOF (Matrix-Assisted Laser Desorption Ionization – Time of Flight) mass spectrometry is a cutting-edge analytical technique enabling the rapid, accurate and reliable identification of microorganisms (bacteria, yeasts, molds) from their protein profile. Used in microbiology laboratories, this method is increasingly integrated into industrial sectors (pharmaceutical, cosmetic, food, animal health) for contamination control and microbiological monitoring .
What is the MALDI-TOF method?
MALDI -TOF mass spectrometry method based on the desorption-ionization of a sample by a laser , assisted by a chemical matrix . The ions thus formed are then separated according to their time of flight (TOF) , i.e. the time they take to travel a fixed distance in an electric field.
Each microorganism has a specific protein fingerprint , mainly consisting of ribosomal proteins . This fingerprint is compared to a spectral database , allowing reliable identification down to the species level .
How the MALDI-TOF method works
MALDI-TOF analysis follows these steps:
- Sample preparation : A bacterial colony is deposited on a target plate, mixed with a crystallizing matrix .
- Laser ionization : A UV laser vaporizes the matrix, releasing the proteins in the sample as ions.
- Time-of-flight (TOF) measurement : ions pass through a flight tube; their speed depends on their mass . They are detected upon arrival.
- Generation of the mass spectrum : the profile obtained (protein fingerprint) is compared to a database to identify the microorganism.
Technical characteristics of MALDI-TOF
- Spectrometry type : MALDI-TOF. This is a mass spectrometer combining a matrix-assisted laser ionization (MALDI) source and a time-of-flight (TOF) analyzer.
- Quick preparation : a few minutes
- Species identification : based on ribosomal proteins
- Matrix used : sinapinic acid or α-cyano-4-hydroxycinnamic acid (HCCA)
- Database : commercial or specific (environmental bacteria, typical contaminants)
- Detection limits : a few thousand cells are sufficient
- High reproducibility , validatable and traceable method
For which matrices?
MALDI-TOF mass spectrometry is applied to microbial colonies cultured or isolated from various types of samples:
Main industrial applications
The MALDI-TOF method is widely used for microbiological diagnosis , but also in industry for critical quality control applications :
Léa Géréec
Technical and scientific advisor
