Fungi and actinobacteria in moisture-damaged building materials — concentrations and diversity

Modern building materials, once moistened, may provide ecological niches for various microbes that have not been well characterized. The aim of the current study was to determine whether fungal genera and actinobacteria were associated with seven types of moisture-damaged building materials by systematically describing the mycobiota and enumerating fungi and bacteria in these materials. Microbial analyses were obtained from 1140 visibly damaged samples of building material, viz. wood, paper, non-wooden building boards, ceramic products, mineral insulation materials, paints and glues, and plastics. Fungal and bacterial concentrations correlated well (r=0.6). The range of fungi and bacteria numbers was between 100 and 108 cfug−1 in all materials, but significant differences in counts were observed between materials. Highest median concentrations of fungi were observed in wooden and paper materials, and lowest in samples of mineral insulation, ceramic products, and paints and glues. Concentrations of viable bacteria in mineral insulation materials were significantly lower than in wood, paper, ceramic products and plastics. A rich variety of fungi was found in wooden materials, with Penicillium and yeasts occurring most frequently. In paper materials, a clear difference from wood was the more frequent occurrence of Cladosporium and Stachybotrys. The most distinctive finding in gypsum boards was that Stachybotrys was common. Ceramic products and paints and glues seemed to favour Acremonium and Aspergillus versicolor. Yeasts and members of the Sphaeropsidales occurred often in parallel in most materials. This study confirms that microbial growth occurs in many different building materials and shows associations between fungal genera and the type of material.