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Heteroduplex DNA Fingerprinting of Penicillium Brevicompactum from House Dust
James A. Scott, Neil A. Straus1, Bess Wong Department of Botany, University of Toronto E-mail: jscott@sporometrics.com

It is widely believed that many osmotolerant microfungi, including toxigenic species of Aspergillus and Penicillium proliferate on indoor substrata such as dust and broadloom even in the absence of appreciable moisture. This hypothesis has been offered as an explanation for the disproportionate abundance of propagules of these species in indoor environments, relative to their representation in outdoor reservoirs such as air and soil.

We obtained several thousand isolates of Penicillium from 367 homes in southwestern Ontario, Canada. From these, 75 isolates of P. brevicompactum representing 54 houses were selected based on micromorphological and physiological uniformity. Sequences of PCR-amplification products of polymorphic genetic loci were compared between isolates using heteroduplex mobility assay (HMA), demonstrating two primary, genetically divergent groups which appear to be stable, clonally-reproduced lineages within the dust mycoflora. These clones are distributed throughout the sample population and co-exist at several sites, suggesting that in absence of objective moisture problems, the principal amplifiers of P. brevicompactum lie outside the building environment. It is possible that mechanical / filtration effects (e.g. differential removal of propagules by vacuum cleaning and elutriation in air conveyance systems), and the relatively long spore viabilities of trichocomaceous anamorphs play a significant role in concentrating propagules of these microfungi in homes.