Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 4, 1997
Publication Date: N/A
Interpretive Summary: Species in the fungal genus Fusarium produce toxins that impact on human health and safety. One species identified as F. graminearum has been cultured as a protein source for human consumption in England for over a decade under the registered trade name Quorn. The purpose of this study was to investigate the relationships and identity of the Quorn strains using biochemical methods [i.e., molecular genetics] and microscopy, and by examining these strains and Quorn food products sold commercially in England for the presence of zearalenone and trichothecene toxins. Results from the molecular genetic, morphological, and toxin analyses each independently indicate the Quorn fungus previously identified as F. graminearum is a toxigenic species, F. venenatum. Toxin analyses demonstrated that Quorn strain NRRL 25416 can produce four different trichothecenes. However, no toxins were detected from the analysis of the three commercial Quorn products tested. Results of the molecular genetic analyses provide a means for predicting toxin production for the many species of Fusarium for which these secondary metabolites have not been characterized.
Technical Abstract: Molecular phylogenetic, morphological, and mycotoxin data were obtained in order to investigate the relationships and identity of the Quorn mycoprotein fungus within Fusarium, and to examine Quorn strains and commercial Quorn food products for trichothecene mycotoxins. All of the Quorn strains examined were morphologically degenerate except for NRRL 25139 which produced chlamydospores in recurved terminal chains together with sporodochial conidia diagnostic of Fusarium venenatum. Phylogenetic analyses of aligned DNA sequences obtained via the polymerase chain reaction from the nuclear 28S ribosomal DNA, nuclear ribosomal internal transcribed spacer (ITS)1 region, and -tubulin gene exons and introns further indicate the Quorn fungus is Fusarium venenatum, rather than F. graminearum as previously reported. Bootstrap and decay analyses provide strong support for a monophyletic lineage containing F. venenatum and several other type A trichothecene-producing species while authentic isolates of F. graminearum were nested in a separate clade of species that produce type B trichothecenes and/or zearalenone. Analysis of mycotoxins from rice cultures inoculated with Quorn strain NRRL 25416 revealed that four type A trichothecenes are produced but at low levels relative to strain NRRL 22198 of F. venenatum. No trichothecene mycotoxins, however, were detected from the analysis of three commercial Quorn products marketed for human consumption in England.