A recent study suggests that bacteria thrive more readily on untreated than treated wood surfaces. The finding has implications for hygiene in both homes and public spaces.
A University of Helsinki study investigated bacterial adhesion, survival and transmission on untreated and treated wood surfaces under both laboratory and field conditions.
The laboratory work focused on Staphylococcus epidermidis, a bacterium that forms part of the skin's normal microbiota; and Pseudomonas aeruginosa, a potential pathogen. The first is a common and usually harmless bacterium that occurs naturally on human skin. It is a good example of bacteria that pass from skin to surfaces in everyday life. The latter meanwhile can cause infections, particularly among vulnerable groups, and is known for its ability to survive in harsh conditions.
The study found that more bacteria were present on untreated wood surfaces and remained more viable than those on treated wood.
"When a wood surface had been treated, both the number of bacteria and the variety of species were lower. In other words, surface treatment affects surface microbiota. In doing so, it may influence hygiene and health risks. Untreated wood, on the other hand, may help preserve beneficial microbes," says Doctoral Researcher Elina Kettunen.
The study exemplifies how mutually beneficial laboratory and field experiments can be. Laboratory conditions allowed for the controlled study of bacterial behaviour on wood surfaces, while experiments in public spaces demonstrated how the phenomenon manifests in real microbial communities.
"S. epidermis, for instance, survived better on untreated wood under laboratory conditions. In field experiments, a greater number of diverse and more viable bacteria were observed on untreated surfaces. This indicates that the natural properties of wood affect microbial communities. However, environmental factors and competition between microbes alter the intensity of these effects," says Kettunen.
Material selection can affect microbiota
As the study examined a limited number of materials and only two bacterial species in laboratory conditions, further research is needed to establish long-term effects. Nevertheless, the findings offer practical evidence of how material selection may influence the microbiota that forms on surfaces.
"Indoor environmental health, material durability and microbial management are all central concerns in construction. The study's findings could be applied in settings such as furniture and walls, where the choice of material and surface treatment can affect hygiene and surface microbiota alike. In time, this may pave the way for developing wood materials and surface treatments that are more hygienic, or even so-called probiotic," notes Associate Professor of Wood Material Science Tuula Jyske.
Original article:
Elina Kettunen, Julia Ahlblad, Mika Kurkilahti, Pekka Varmanen, Kirsi Savijoki, Tuula Jyske, From antimicrobial activity to microbial ecology: Untreated and treated wood surfaces shape bacterial survival and community diversity in indoor environments, Journal of Hazardous Materials Advances, Volume 22, 2026, 101090, ISSN 2772-4166,
