Evolutionary relationships among members of the fungal form-genus Stachybotrys, with emphasis on indoor-occurring taxa and the phylogenetic distribution and evolution of the trichothecene biosynthetic gene, tri5.
Published: 2006
Language: eng
Number of pages: 267
ISBN-13: 9780494218518
Description: Members of the genus Stachybotrys are haploid mitosporic fungi capable of dense colonization of water-damaged building materials such as drywall and ceiling tiles. Current interest in Stachybotrys however, is due to their ability to produce protein-synthesis inhibiting, trichothecene mycotoxins, which have been suggested as linked to a variety of putatively indoor-environment related illness. I used five sequence-based markers and a geographically and otherwise broad set of isolates to investigate the degree of divergence among a set of indoor isolates consistent with the traditional S. chartarum morphotype. Phylogenetic analyses supported the recognition of two distinct phylogenetic lineages within the morphotype. For the lineage most commonly found in Ontario indoor environments, I then used AFLP-based markers to investigate the degree of genetic diversity and pattern of haplotype distribution. Results of cluster and linkage analyses suggested both a strong clonal component and some level of recombination in the evolutionary history of this set of isolates. With respect to distribution, I found no correlation between geographic and genetic distances and the distribution of isolates within a single multi-floor institutional building suggested that indoor isolates had been largely drawn from some, as yet unidentified, external reservoir. Lastly, I explored the broader evolutionary relationships of indoor-occurring and other species of Stachybotrys using both nrDNA and protein-encoding genes and found that species of Stachybotrys partitioned into three strongly supported intrageneric lineages. Two of these clades included common indoor-occurring species. Bayesian analysis suggested that the trichothecene biosynthetic gene, tri5, might be incongruent with the combined phylogeny for this group. Maximum likelihood bootstrap analyses and SH-test results however, did not support this interpretation. Moreover, PAML sites rates analysis indicated that the sampled portion of tri5 was highly conserved suggesting that, for many homoplasic sites, identity between divergent taxa at the amino acid level might be the result of stochastic processes. Results of Southern analyses supported one intrageneric clade, including isolates representing morpho-species S. albipes, S. bisbyi  and S. parvispora, as lacking the tri5  gene. The latter results have broad implications in terms of the phylogenetic distribution of trichothecene biosynthetic pathway genes among ascomycetous fungi.**This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office.
Notes: Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0074.

Thesis (Ph.D.)--University of Toronto, 2006.

Electronic version licensed for access by U. of T. users.