Discrimination of Euglena gracilis strains Z and bacillaris by MALDI-TOF MS

Euglena gracilis is used as model organism for various microbiological, molecular biological and biotechnological studies. Its most studied wild-type strains are Z and bacillaris, but their discrimination by standard molecular methods is difficult. Therefore, we decided to test the suitability of MALDI-TOF MS (matrix-assisted laser desorption/ionization-time of flight mass spectrometry) for identification of E. gracilis and for discrimination of these two strains possessing functional chloroplasts. MALDI-TOF MS profiling was also tested for two white (non-photosynthetic) stable E. gracilis mutant strains W_gm ZOflL and W₁₀ BSmL.

We have successfully obtained main spectrum profiles (MSPs) of E. gracilis strains Z, SAG 1224-5/25 and bacillaris, SAG 1224-5/15 using protein extraction procedure. Subsequent MALDI-TOF MS profiling of a number of tested samples and the comparison of the obtained protein profiles with our in-house database including MSPs of both strains have revealed that these two strains can be easily distinguished by MALDI-TOF MS based on score values over two in most cases. This method has also confirmed the ancestry of white mutant strains W_gm ZOflL and W₁₀ BSmL, originally derived from strains Z and bacillaris, respectively.

MALDI-TOF MS is suitable, accurate and rapid method for discrimination of E. gracilis strains.

These results can have broad practical implications for laboratories cultivating various strains of euglenids, and they can be applied for their discrimination by MALDI-TOF MS.