Microorganisms such as bacteria, viruses, and fungi are present everywhere, in the air we breathe, on the surfaces we touch, and even on our skin.
Yet researchers still know little about which species dominate in different environments.
To learn more, Professors Håvard Kauserud and Inger Skrede from the University of Oslo investigated the fungal and bacterial composition in Norwegian homes and daycares.
Volunteers across the country received swabs and gloves to collect dust samples from doorframes, which they then mailed back to the laboratory.
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The same procedure was followed in selected daycare centers.
DNA from each sample was extracted and sequenced, producing millions of data points that revealed the complex microbial communities hidden in everyday spaces.
Bacteria in different environments
The results published in Microbial Ecology showed a clear distinction between the two environments.
In private homes, mold species were most prevalent, while yeasts dominated in daycares.
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According to the researchers, the difference may stem from the close relationship between yeasts and humans, these organisms naturally live on our skin and in our intestines.
Daycares, where many children spend long hours in close contact, may therefore provide ideal conditions for yeasts to thrive.
The study also revealed that children have a more diverse skin mycobiom, the part of the microbiome composed of fungi, than adults, which may contribute to this imbalance.
Extreme conditions indoors
Despite our perception of homes as clean and dry, researchers note that these spaces actually represent extreme living conditions for fungi.
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The species that survive indoors resemble those found in harsh natural environments such as mountain rocks or deep-sea sediments.
Outdoor fungi also make their way inside through clothing, footwear, and air circulation, further enriching the microbial mix.
Whether these differences have any health implications remains unclear.
The researchers emphasize, however, that mold growth caused by water damage can be harmful, particularly for individuals with weakened immune systems.
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Further studies would be needed to determine possible links between indoor fungal diversity and human health.
This article is based on information from Forksning.no og Microbial Ecology.
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