Laboratory-based investigation of the materials' water activity and pH relative to fungal growth in internally insulated solid masonry walls.

This project investigated fungal growth conditions in artificially contaminated interfaces between solid masonry and adhesive mortar for internal insulation. The project comprised several laboratory experiments: test of three fungal decontamination methods; investigation of development of fungal growth in solid masonry walls fitted with five internal insulation systems; and investigation of volatile organic compounds (VOC) diffusion through materials and whole insulation systems. One aim was to examine whether the alkaline environment (pH > 9) in the adhesive mortars could prevent fungal growth despite the water activity (aw ) in the interface exceeds the level (aw  > 0.75) commonly considered critical for fungal growth. The findings indicate that do-it-yourself decontamination solutions were inadequate for removal of fungal growth, while professional solutions were successful. However, the choice of decontamination method was of minor importance in the case of application of internal insulation with high pH adhesive mortar, as the high pH adhesive mortars were found to inactivate existing growth and prevented spore germination during the experimental period. The three tested VOCs were capable of diffusing through most of the examined products and could potentially affect the indoor air quality.

Rapid detection and identification of Stachybotrys and Chaetomium species using tissue PCR analysis.

Indoor fungi are a worldwide problem causing negative health effects for infected building's occupants and even deterioration of building structures. Different fungal species affect buildings and their inhabitants differently. Therefore, rapid and accurate identification of fungi to the species level is essential for health risk assessment and building remediation. This study focuses on molecular identification of two common indoor fungal genera: Stachybotrys and Chaetomium. This study proposes two new DNA barcode candidates for Stachybotrys and Chaetomium: the gene encoding mitogen activated protein kinase (hogA) and the intergenic region between histone 3 and histone 4 (h3-h4) as well as it introduces a rapid - 3.5h - protocol for direct Stachybotrys and Chaetomium species identification, which bypasses culture cultivation, DNA extraction and DNA sequencing.

Visualization of the structural changes in plywood and gypsum board during the growth of Chaetomium globosum and Stachybotrys chartarum.

Fungal growth in indoor environments is associated with many negative health effects. Many studies focus on brown- and white-rot fungi and their effect on wood, but there is none that reveals the influence of soft-rot fungi, such as Stachybotrys spp. and Chaetomium spp., on the structure of building materials such as plywood and gypsum wallboard. This study focuses on using micro-computed tomography (microCT) to investigate changes of the structure of plywood and gypsum wallboard during fungal degradation by S. chartarum and C. globosum. Changes in the materials as a result of dampness and fungal growth were determined by measuring porosity and pore shape via microCT. The results show that the composition of the building material influenced the level of penetration by fungi as shown by scanning electron microscopy (SEM). Plywood appeared to be the most affected, with the penetration of moisture and fungi throughout the whole thickness of the sample. Conversely, fungi grew only on the top cardboard in the gypsum wallboard and they did not have significant influence on the gypsum wallboard structure. The majority of the observed changes in gypsum wallboard occurred due to moisture. This paper suggests that the mycelium distribution within building materials and the structural changes, caused by dampness and fungal growth, depend on the type of the material.