Microbial diversity in different building materials exposed to high and lower humidity conditions

Low indoor air quality (IAQ) has been shown to increase health problems in people living or working in buildings suffering moisture, mold and decay problems. Humidity exceeding the tolerances of materials causes VOC emissions, microbial growth and decay which lead to low IAQ and building damage. The critical conditions needed for the development of mould and decay fungi have been modelled for different building materials. However, current knowledge of indoor microbes growing on building materials relies on culture-based methods and more advanced molecular biological techniques should be employed to study the complex microbial communities in building materials. In this research molecular biological techniques were optimized and used to study microbial diversity in building materials exposed to different moisture conditions. Wood-, concrete- mineral and polyester wool-based naturally contaminated and inoculated building materials were exposed to different humidity conditions (relative humidity 90% and 98%) in laboratory-scale experiment. The DNA extraction method was optimized to different building materials and microbial communities were studied by fungal ITS region targeted PCR-DGGE and sequencing. Fungal communities differed between building materials and humidity conditions. In RH 90% the majority of the sequences obtained belonged to genus Aspergillus. As expected, in RH 98% the fungal community was more diverse containing e.g. genera Penicillium, Aspergillus and Oidiodendron. The fungal diversity was highest in wood-based building materials. Molecular biological techniques provide more information about microbial communities in moisture damaged building materials and these techniques could offer new tools to understand the complicated relationship between moisture, material, microbes and IAQ.