Researchers uncover gold nanoparticles in spruce needles
In a surprising twist to the usual gold hunt, scientists have found trace gold nanoparticles concentrated within the needles of Norway spruce trees. The study, published on August 28 in Environmental Microbiome, suggests that endophytic bacteria living inside the trees may help concentrate gold particles taken up from the soil via the roots. While the discovery won’t spark a new gold rush by harvesting spruce needles, it could change how geologists locate buried gold deposits.
The biology behind the find
The researchers describe a form of biomineralization in which living organisms influence mineral formation. In this case, tiny gold particles are drawn into the tree tissues and then coordinated by the resident microbial community, known as endophytes. “Endophytes are symbiotic microorganisms that assist with hormone production and nutrient uptake, among other functions,” said lead author Kaisa Lehosmaa, an ecologist at the University of Oulu in Finland. The team proposes that the bacteria help segregate soluble gold particles into more stable forms, potentially reducing toxicity and enabling the tree to tolerate the mineral.
Where the gold hides—and how much
The team studied spruce trees near the Kittilä mine in northern Finland, Europe’s largest gold producer. Between 138 needle samples from 23 trees, four trees contained gold nanoparticles. These nanoparticles were encased by biofilms produced by bacterial genera such as P3OB-42, Cutibacterium, and Corynebacterium. Biofilms—layers of sugars and proteins secreted by bacteria—facilitate the persistence of these particles within plant tissues.
The discovery is notable not for the value in the needles themselves—nanoscopic particles are about a millionth of a millimeter in size—but for what they may reveal about the environmental signals that hint at subsurface gold. The gold appears to be present as tiny particles that the trees partly concentrate and stabilize, rather than as large mineral deposits within the needles.
Endophytic microbes and metal accumulation
Endophytes are increasingly recognized as key players in how plants absorb and manage metals. In environments with elevated metal availability, some plants and their microbial partners accumulate metals in tissue. The observed decrease in microbial biodiversity in needles with gold suggests a selective environment where certain bacteria thrive alongside mineral accumulation. This trend aligns with other plant studies that report reduced microbial diversity in tissues with high metal loads, possibly due to antimicrobial pressures or specialized ecological niches.
Implications for gold exploration
While you won’t be cashing in on spruced-up needles anytime soon, the findings may help map hidden gold. Lehosmaa notes that screening for specific endophytic bacteria in plant leaves could serve as a noninvasive indicator of underlying gold deposits. If a consistent association between particular bacterial communities and gold-bearing geology is established, geologists could use plant microbiome signals to target prospecting efforts more efficiently.
What comes next?
Further work will aim to determine how universal this mechanism is—whether it occurs in other tree species or specific to the Norway spruce—and to quantify how reliably endophyte profiles predict subterranean gold. The study also raises questions about the ecological roles of these microbes in metal-rich environments and how environmental factors, such as mining activity, might influence plant-microbe-mineral interactions.
Bottom line
The discovery of gold nanoparticles within spruce needles, guided by a hidden world of endophytic bacteria, offers a fresh lens on environmental microbiomes and their potential in mineral exploration. It’s a reminder that the smallest organisms can influence the distribution of valuable minerals in surprising ways—and that biology may one day help focus the search for gold beneath the surface.
