Abstract

Abstract

Abstract

The quality of the indoor environment is very important and affects our daily life and well-being, whether it is at home, at work, at institutions or any other building that we use. The indoor environment is very complex and many individual parameters act together to a given quality. One of the parameters that – for good reasons – have been central for decades is the mycobiota. The fungi, that thrive in the built environment whether we like it or not. A specific focus has been on the molds that do not destroy the physical strength of a building, but have a severe effect on human health. The body of knowledge within this theme is overwhelming, but still it is impossible to synthesize all the data into error-free operations and solutions. There are too many gaps, and new gaps are discovered on a regular basis. A main reason is that mycology is in the midst of a booming technological development. The classical mycological philosophies (values) are being challenged by a massive data-driven wave that has moved mycology into the information-age. Especially the rapid developing DNA technologies have changed the mycological systematics from being phenotypic based to mainly phylogenetic based. In addition, many analyses are more objective than former time’s very subjective judgements of phenotypic traits. The resolution between taxonomic entities has also improved dramatically, which means that the number of fungal species are increasing. Often old broad species are split into several new more narrow circumscribed species. For the built environment, this means that the number of species detected are increasing by validated identifications. Good. The drawback is that the phenotypic traits – the functionality – are missing, meaning no information on the mycobiota and its effect on human health, or no explanation why it is exactly these species that are present. The way forward to improve this situation is a holistic approach using available powerful computational capabilities. A multi-disciplinary characterization of the fungal phenotypes that should also cover their physiological, ecological and metabolic traits should interact with the modern taxonomic schemes and the DNA sequence databases used by consensus analyzes to obtain a true picture of the fungal species. This will generate a deeper understanding of the fungal organism in itself, how the fungal communities develop in the built environment, and fungal interaction with building users and the effect on human health. The holistic approach will lead to guidelines for remediation and prevention of unwanted mold growth in the built environment. Furthermore, the improvement of technical installations in our buildings that monitor and regulate the physical environment, energy consumption etc. will give us a unique opportunity for a true big-data based understanding of indoor quality with a focus on molds and healthy homes.

Abstract

Fungi are known for their degradation abilities, mainly of organic matter. However, there are increasing evidences of their role in mineral materials deterioration as well including building materials. We have investigated the possible involvement of fungi in the eefflorescence phenomenon of floor tiles inside building. Fungi were isolated from eefflorescence site and their abilities of degradation and use of the tile materials were studied in axenic culture. The efflorescence was seen as salt migration on top of a tile with a needle-like re-crystallization on the surface. Three black molds fungi were isolated from the site. The fungi were shown to have selective growth and stone dissolution of the different tile fractions (dolomite, calcite or calcite–apatite mineral) in low-nutrition medium. The growth of the fungi in the presence of the stones fraction, and the dissolution the fraction was accompanied by production and release of organic acids into the culture medium. The fungi were able to use the dissolved tiles materials as nutritient sources. This indicates that fungi may contribue to the natural physio-chemical process of efflorescence.

Abstract

Extreme habitats are not only limited to natural environments, but also exist in manmade systems, for instance, household appliances such as dishwashers. Research on dishwasher microbiome started in 2011 with the discovery that black yeast, especially opportunistic Exophiala dermatitidis, colonizes rubber seals of domestic dishwashers. This global phenomenon attracted even more attention with the isolation of other fungal human opportunistic pathogens from dishwashers, such as Candida parapsilosis, Exophiala phaeomuriformis, Aureobasidium melanogenum, Fusarium dimerum and Saprochaete clavata. Due to the emphasis on fungi, the bacterial community of dishwasher remained initially unexplored. To address this issue, bacterial and fungal diversity in biofilms isolated from rubber seals of 24 different household dishwashers was investigated using next-generation sequencing. Microbiome resulted in bacterial genera such as Pseudomonas, Escherichia, and Acinetobacter, known to include opportunistic pathogens that were represented in most samples. The most frequently encountered fungal genera belong to Candida, Cryptococcus, and Rhodotorula, also known to include opportunistic pathogenic representatives. This study also showed how specific abiotic conditions of the dishwashers impact the abundance of microbial groups and the interkingdom and intrakingdom interactions in these biofilms. The age, usage frequency, and hardness of incoming tap water of dishwashers had the most significant impact on bacterial and fungal community compositions. Candida spp., found with the highest prevalence (100%) in all dishwashers, is probably the first colonizers in new dishwashers. In mixed bacterial-fungal biofilms, early adhesion, contact, and interactions were vital in the process of biofilm formation. Mixed complexes of bacteria and fungi provide a preliminary biogenic structure for the establishment of biofilms. Pairwise correlations in tested microbiomes showed that certain bacterial and fungal groups co-occur. Evaluation of fungal abundance per 1 cm² of rubber seals revealed the highest levels for E. dermatitidis, followed by E. phaeomuriformis and C. parapsilosis. Isolation of cultivable bacterial and fungal strains and further screening tests showed which bacterial species gain in biomass by incorporating E. dermatitidis in the biofilm and thus contribute to its promotion and abundance. The significance of our research is in identifying the microbial composition of biofilms formed in a broadly used household appliance, in describing how diverse abiotic conditions affect the composition of mixed fungal bacterial microbiota, and which key members were represented in early colonization.

Abstract