A new study published in Environmental Microbiome reports for the first time a direct association between microbes living inside Norway spruce (Picea abies) needles and the formation of gold nanoparticles, a finding that could inform lower‑impact mineral exploration and new remediation approaches. It comes as researchers from the University of Oulu and the Geological Survey of Finland collected 138 needle samples from 23 spruce trees on a satellite deposit of the Kittilä gold mine and detected gold nanoparticles in needles from four trees, with the particles consistently occurring beside bacterial biofilms.
“Our results suggest that bacteria and other microbes living inside plants may influence the accumulation of gold in trees,” Postdoctoral Researcher Kaisa Lehosmaa said, describing how soluble gold in soil water is carried into shoots and then precipitated by needle‑associated microbes into solid, nanosized particles.
Wood Central understands that DNA sequencing of the biofilms revealed a higher prevalence of bacterial groups such as P3OB‑42, Cutibacterium and Corynebacterium in gold‑containing needles, suggesting those taxa may mediate the transformation of dissolved gold into solid particles.
“Such biogeochemical methods have already been used in mineral exploration, but this new research enhances our understanding of what is actually happening in the process,” said Research Professor Maarit Middleton of the Geological Survey of Finland. Professor Anna Maria Pirttilä of the University of Oulu added that “these so‑called endophytic microbes may play a role in plants’ biomineralisation processes,” a pathway that remains poorly understood because biomineralisation events are often sporadic and highly localised.
The study’s authors emphasise that the detected gold exists as dust‑scale nanoparticles invisible to the naked eye and far too small to be collected for commercial extraction, but their presence offers a potential biosignal for exploration. “This suggests that these specific spruce‑associated bacteria can help transform soluble gold into solid particles inside the needles. This insight is useful, since screening for such bacteria in plant leaves may facilitate gold exploration,” Dr Lehosmaa said.
Beyond prospecting, the findings point to remediation possibilities. “Metals can, for example, precipitate within moss tissues. Studying biomineralisation also allows us to explore how bacteria and microbes living in aquatic mosses could help remove metals from water,” Dr Lehosmaa said. The research was supported by the Geological Survey of Finland, the Academy of Finland and the KH Renlund Foundation and was published on August 28, 2025.
For more information: Lehosmaa, K., Wäli, P.R., Sutinen, A. et al. Biomineralized gold nanoparticles along with endophytic bacterial taxa in needles of Norway spruce (Picea abies). Environmental Microbiome 20, 113 (2025). https://doi.org/10.1186/s40793-025-00770-x
