MALDI-TOF MS Spectral Variation Is Observed between Fungal Samples Grown under Identical Conditions after Long-term Storage by Cryopreservation, Freeze-drying, and under Oil.

BACKGROUND: Matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) offers a powerful, versatile, and relatively-inexpensive tool for the characterization and/or identification of protein-containing samples. OBJECTIVE: In the case of filamentous fungi, significant variation in MALDI-TOF MS spectra can be observed for growth under different conditions on agar plates, as well as over time for growth on the same medium. We therefore sought to investigate the possibility of additional variance as a result of the preservation conditions prior to culturing. MATERIALS AND METHODS: We investigated Fusarium nygamai IMI 383003, previously preserved by liquid nitrogen cryopreservation, freeze-drying, and storage under oil. RESULTS: Significant spectral differences are observed as a function of preservation conditions prior to culturing on agar plates, under experimental conditions that show high reproducibility between replicate sample preparations and between replicate agar plates used for culturing. CONCLUSION: Storage and cryopreservation conditions can affect MALDI-TOF MS spectra.