Terverticillate Penicillia studied by direct electrospray mass spectrometric profiling of crude extracts: I. Chemosystematics

A chemosystematic study of 339 isolates from all known terverticillate Penicillium taxa was performed using electrospray mass spectrometric analysis of extractable metabolites. The mass profiles were made by injecting crude plug extracts made from cultures grown on Czapek Yeast Autolysate agar (CYA) and Yeast Extract Sucrose agar (YES) directly into the electrospray source of the mass spectrometer. A data matrix was made from each substrate by transferring the complete centroid mass spectrum from 200 to 700 amu as 501 variables to individual columns. No attempt was made to identify ions in the mass profile, but a noise level was applied. Cluster analysis using the correlation coefficient resulted in dendrograms where approximately 75% of the included taxa could be considered segregated in distinct clusters. Standard normalized data (mass spectra) resulted in clear clusters, but grouped taxa dominated by a single intense ion together, whereas logarithmized data revealed finer detail but with a shorter distance between clusters. The overall results showed that substantial taxonomic information can be extracted from mass profiles even when the identity of ions is unknown. ions corresponding to known secondary metabolites were, however, found in all mass profiles. (C) 1997 Elsevier Science Ltd.