Spectral Grouping of Nominally Aspergillus versicolor Microbial-Collection Deposits by MALDI-TOF MS

Abstract

Historical microbial collections often contain samples that have been deposited over extended time periods, during which accepted taxonomic classification (and also available methods for taxonomic assignment) may have changed considerably. Deposited samples can, therefore, have historical taxonomic assignments (HTAs) that may now be in need of revision, and subdivisions of previously-accepted taxa may also be possible with the aid of current methodologies. One such methodology is matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS). Motivated by the high discriminating power of MALDI-TOF MS coupled with the speed and low cost of the method, we have investigated the use of MALDI-TOF MS for spectral grouping of past deposits made to the Centre for Agriculture and Bioscience International (CABI) Genetic Resource Collection under the HTA Aspergillus versicolor, a common ascomycete fungus frequently associated with soil and plant material, food spoilage, and damp indoor environments. Despite their common HTA, the 40 deposits analyzed in this study fall into six clear spectral-linkage groups (containing nine, four, four, four, four, and two members, respectively), along with a group of ten spectrally-unique samples. This study demonstrates the clear resolving power of MALDI-TOF MS when applied to samples deposited in historical microbial collections.

Spectrometric Characterization of Clinical and Environmental Isolates of Aspergillus Series Versicolores

“…Several studies have shown that MALDI-TOF MS can be successfully used to identify fungi in this series. Recently, Reeve et al used MALDI-TOF MS technology to characterize 40 environmental isolates of Aspergillus series Versicolores [ 29 ]. They found consistent identifications with the Bruker database, identifying A. versicolor 2009_137364 MUZ and A. versicolor F51 LLH, which did not belong to the same spectral-linkage groups.…”