Fungal and bacterial colonies growing on weathered wood surfaces

The weathering of wood through abiotic factors has been extensively studied. Much less research has been conducted on the influence of biotic factors on wood in exterior use that is not in ground contact, i.e. use class 3. There is especially a lack of research concerning the influence of the presence of bacterial and fungal communities on the weathering process of wood. The project aim is to identify any synergistic effects between biotic factors such as bacteria (Actinomycetes and Eubacteria) and fungi (Basidiomycota and Ascomycota) and abiotic factors such as light, temperature and moisture on the weathering of wood surfaces in use class 3. This paper presents results such as the amount of colony forming units (CFU), environmental scanning electron microscope analysis, colour changes and moisture content (MC) from preliminary experiments where wood surfaces were either naturally or artificially weathered. In order to study the interactions of fungi and bacteria on wood during the weathering process, the presence of microorganisms on natural weathered oak and Douglas fir surfaces had to be validated first. With the help of a surface contact test, microorganisms on the wood surfaces were transferred to agar plates and consequently incubated so that they could grow in appropriate conditions. Once the microbiological colonies had developed sufficiently, they were separated by selecting sections from the colonies and replated on fresh agar. A microcosm scale experiment, meaning the transfer of one specific bacteria and one fungi together in one petri dish, was carried out. This trial revealed that certain bacteria have an influence on the growth rate of certain fungi. In addition, an artificial weathering test was carried out in a QUV, which allows the degradation of samples using specific and known abiotic degrading parameters. The observation of the artificial weathered wood samples revealed that microorganisms are most definitely present in the QUV test apparatus and may influence the test results.