Detection of Chaetomium globosum, Ch. cochliodes and Ch. rectangulare during the Diversity Tracking of Mycotoxin-Producing Chaetomium-like Isolates Obtained in Buildings in Finland

Abstract

The diversity of <i>Chaetomium-</i>like isolates in buildings in Finland is poorly documented. This paper describes a set of methods for rapid diversity tracking of 42 indoor <i>Chaetomium</i>-like isolates. These isolates were categorized based on their fluorescence emission, ascomatal hair morphology, responses in three bioassays and resistance/sensitivity to the wetting agent Genapol X-080. Thirty-nine toxigenic isolates were identified [<i>Ch. globosum</i> (<i>n</i> = 35), <i>Ch. cochliodes</i> (<i>n</i> = 2) and <i>Ch. rectangulare</i> (<i>n</i> = 2)]. These isolates were identified down to the species level by <i>tef1α</i> gene sequencing. The major toxic substances in the ethanol extracts of the <i>Ch. globosum</i> and <i>Ch. cochliodes</i> strains were chaetoglobosin, chaetoviridin A and C, chaetomugilin D and chaetomin, identified based on HPLC-UV and mass spectrometry data (MS and MS/MS). Ethanol extracts from pure <i>Ch. globosum</i> cultures exhibited a toxicological profile in the boar sperm motility inhibition assay (BSMI), sperm membrane integrity damage assay (SMID) and inhibition of cell proliferation (ICP) assay, similar to that exhibited by pure chaetoglobosin A. Overall, differences in fluorescence, morphology, toxicity profile, mycotoxin production and sensitivity to chemicals were consistent with those in <i>tef1α</i> sequencing results for species identification. The results indicate the presence of <i>Ch. cochliodes</i> and <i>Ch. rectangulare</i> in Finnish buildings, representing a new finding.