Researchers uncover gold nanoparticles in spruce needles
A surprising discovery from northern Finland is shining new light on how plants interact with minerals. In a study published in Environmental Microbiome, scientists report that Norway spruce trees (Picea abies) can concentrate gold nanoparticles in their needles, a feat accomplished with the help of resident, symbiotic bacteria known as endophytes. The finding adds a compelling twist to our understanding of biomineralization, the process by which living organisms form minerals within their tissues.
The study, led by ecologist Kaisa Lehosmaa of the University of Oulu, analyzed spruce trees growing near the Kittilä mine—the largest gold producer in Europe. Researchers collected 138 needle samples from 23 trees and found gold nanoparticles in the needles of four trees. These tiny particles, measuring about a millionth of a millimeter, were not simply passively present; they were closely associated with biofilms created by specific bacteria inside the plant tissues.
What the researchers found
The gold nanoparticles were surrounded by bacterial biofilms composed of genera such as P3OB-42, Cutibacterium, and Corynebacterium. These biofilms are complex mixtures of polysaccharides and proteins secreted by the endophytic bacteria, forming protective and functional layers that help the microbes persist within the plant. The tight association between the nanoparticles and these biofilms strongly suggests that the bacteria play an active role in concentrating the mineral, potentially to mitigate its toxicity to the plant.
Endophytes are known to influence a plant’s hormone production and nutrient uptake, and this study adds a new dimension to their repertoire. By collaborating with these microbes, the spruce needles appear to sequester dissolved gold particles that the trees absorb from water through their roots. This biomineralization process offers a vivid example of how plants and microbes together shape mineral patterns in terrestrial ecosystems.
Why biodiversity matters in metal-rich tissues
The researchers observed a notable pattern: the diversity of bacterial species was lower in needles containing gold. This mirrors other investigations showing that tissues with high metal concentrations can support a less diverse microbial community. The implications are twofold. First, the reduced microbial diversity may reflect a selective environment shaped by metal exposure, where only certain endophytes thrive. Second, the presence of gold-bearing biofilms could serve as a biological proxy for mineral-rich underground formations.
Implications for mineral exploration
Despite the minute size of the nanoparticles, the discovery has practical promise. Lehosmaa notes that screening for bacteria in plant leaves could become a tool for locating gold deposits beneath the surface. If specific endophytes consistently associate with mineral-rich environments, researchers could use the presence of these microbes in needles as a non-invasive, preliminary screening method for exploration campaigns.
“Screening for such bacteria in plant leaves may facilitate gold exploration,” Lehosmaa said. While the idea is not to harvest gold directly from trees, the method could help identify promising regions for traditional mining or more targeted sampling, reducing costs and environmental impact in early-stage exploration.
What this means for science and forestry
The finding enriches our understanding of plant–microbe interactions and the broader field of biomineralization. It shows that the micro-world inside trees can influence mineral dynamics in ways previously unimagined. For forestry science, the study highlights the need to consider endophyte communities when evaluating tree health and nutrient cycling, especially in metal-rich landscapes and near mining operations.
As researchers continue to investigate the mechanisms behind endophyte-driven mineral accumulation, this work may inspire new bioscience approaches to mineral sensing and environmental monitoring. The spruce trees near Kittilä have offered a peek into a hidden world where small microbes and tiny gold particles intersect, with potential consequences for science, exploration, and the sustainable use of natural resources.
Key takeaways
- Gold nanoparticles were found in the needles of some Norway spruce trees near a Finnish gold mine.
- Endophytic bacteria form biofilms that likely help isolate and concentrate the mineral within plant tissues.
- The discovery could pave the way for microbe-based screening tools for gold exploration.
- Category: Science / Environment
- Tags: gold nanoparticles, biomineralization, endophytes, spruce, Environmental microbiome, biofilms, mineral exploration
