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Microbial activity can have an important impact on the durability of building materials. It is important to understand this activity in order to select appropriate treatment strategies for the repair and restoration of buildings and monuments. This paper describes the microorganisms which can modify the properties of building materials such as concrete, mortars, composites, timber, gypsum, etc., as well as the mechanisms responsible for deterioration of these materials. The information provided by the members of TC 183-MIB via a questionnaire is discussed. Techniques currently utilised and areas requiring further study are identified. In addition to the references, a list of publications for further reading completes this article.

The alteration and weathering of stone is basically determined by natural and anthropogenic impacts influencing various physical, chemical and biological damage factors at the object site. Whether as direct or catalytically enhancing factor, the biodeterioration of stone is coupled with nearly all environmentally induced degradation processes: the presence of the one makes deterioration by the other all the more effective. The bioreceptivity of stone is described by its structure and chemical composition, while the intensity of the microbial contamination is determined by the referring climatic conditions and the anthropogenic euthrophication of the atmosphere. The microflora improves the nutrient and moisture-restricted growth conditions on building stones by the formation of surface-covering biofilms. Besides the aesthetical impairment caused by the coloured biopatina, the biofouling effect promotes even “abiotic” deterioration processes due to the alteration of the material structure as well as their thermo-hygric properties; in addition, mechanical pressure due to the shrinking and swelling of the colloidal biofilms might cause a further weakening of the mineral lattice. Acidolytic and oxido-reductive biocorrosion processes complete the biodeteriorating attack of stone acting as a preliminary precursor for the latter formation of detrimental crusts. Suitable and reliable methods for the detection of biodeterioration processes are available, but only the interdisciplinary diagnosis and evaluation of the entire decay process of stone allows the formulation of adaequate countermeasure strategies. In case the significance of biodeterioration impacts is proven, the possible effects of the microbial contamination on cleaning procedures, protective treatments as well as biocidal applications has to be considered. This paper will give a comprehensive overview to the biodeterioration of stone and stresses the practical relevance for the conservation.

To prove and evaluate the fungal load, present indoors identification of fungi up to species level is prerequisited. Therefore, the set-up of an external quality assurance system and the qualification of the lab workers will be required. In 2001, the working party "Quality Assurance - Fungi in Indoor Environments" - initiated by the Health Service, Baden-Wurttemberg (LGA BW), established an inter-laboratory test entitled "Identification of Indoor Fungi". Until now, 2 inter-laboratory tests are carried out based on pure cultures. In every inter-laboratory test 50 laboratories participated. Results will be represented and discussed. Carrying out the inter-laboratory test internationally is planned.

Quality control is universally recognised as fundamentally important in ensuring that diagnostic laboratories are performing appropriate tests at acceptable levels of competence. Therefore, the working group "Quality assurance--Fungi in Indoor Environments" which was initiated by the Public Health Service Baden-Württemberg (LGA BW) started with the external quality assurance in the diagnosis of indoor fungi in autumn 2001. Up to now we carried out the third mailing based on pure cultures. The results are reported and will be discussed. Exchanging experience on the international level is intended.