A new study from northern Finland suggests that tiny partners living inside trees may help shape precious metals. Researchers working in a boreal forest found microscopic gold particles within the needles of Norway spruce and, for the first time, connected those particles to specific bacteria residing inside the needles. The discovery hints at a greener approach to mineral exploration and raises the possibility that similar biology could help remove metals from mining-impacted waters.

A Simple Question with Wide-Ranging Consequences

The research set out to test a straightforward idea: are microbes living inside spruce needles associated with the presence of gold nanoparticles, and if so, what does that mean for plants, microbes, and mineral prospecting? Geologists already know that buried deposits shed metal ions as rocks weather and bacteria act on them. Those ions move into soil water, where plant roots absorb a mixture of nutrients and trace metals. Sensitive instruments can detect those traces in vegetation, snow, and soils. The team asked whether the needle microbiome is part of this pathway and whether it helps transform dissolved gold into solid particles.

Why Lapland’s Spruces Were the Perfect Test Case?

Scientists from the University of Oulu and the Geological Survey of Finland focused on trees growing above a known gold system in Finnish Lapland, near a satellite deposit of the Kittilä gold mine. That location increased the odds that minute amounts of gold would move through groundwater into roots and up to the canopy. As Research Professor Maarit Middleton of GTK explained, biogeochemical tools have been used in exploration for years, and this work helps clarify what is happening inside the plant during that process.

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Inside the Needles: How the Team Looked for Gold and Microbes

The study analyzed 138 needle samples collected from 23 Norway spruce trees and ran two parallel investigations. One track searched for gold nanoparticles using field-emission scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, a pairing that can confirm whether a bright, dense dot in the microscope carries gold’s characteristic signal. The other track sequenced the 16S rRNA gene to map the communities of bacteria living within the needles. Gold nanoparticles were confirmed in four trees. Where gold turned up, the particles often sat next to clusters of bacterial cells embedded in biofilms, the protective, sticky matrices that allow microbes to live in tight communities on surfaces. The physical proximity of gold specks, bacterial cells, and biofilm structures provided a strong visual clue that biology is involved.

Microbial Fingerprints Associated with Gold

DNA sequencing highlighted bacterial groups that were more common in needles containing gold particles. Taxa such as P3OB-42, Cutibacterium, and Corynebacterium appeared more frequently alongside the confirmed gold signals. The pattern suggests that spruce-associated bacteria help transform soluble gold into solid nanoparticles inside the needles. The authors note that screening for these microbial signatures in plant tissue could add a new layer to mineral exploration, guiding survey crews toward the right targets with less disturbance.

How Biofilms Could Turn Dissolved Gold into Solid Particles?

Gold can travel through soils and plant tissues in a dissolved ionic form. Inside a needle, biofilms create tiny microenvironments that shift pH, redox conditions, and available ligands. Those shifts can make dissolved gold less soluble, encouraging it to precipitate as nanosized particles. Plants often compartmentalize metals to protect essential processes, while microbes benefit from the shelter and chemistry of biofilms. The study offers preliminary evidence that water carries soluble gold into needles and that resident microbes help convert that gold back into solid form.

Not Every Tree Glitters, and That Matters

Gold particles did not appear in every tree, which fits what scientists know about plant hydraulics and microbiomes. Trees draw from different water pathways, and their microbial communities vary by branch, season, and stress. Needles with more gold tended to have fewer bacterial types overall, although the communities did not split into two completely separate camps. The co-location of particles and microbes is compelling, yet it is not a real-time movie of a single bacterium reducing gold. Pinning down cause and effect will require targeted experiments that follow the transformation step by step.

What This Means for Greener Mineral Exploration?

Plant-based geochemical surveys already help explorers detect buried deposits. The microbial angle sharpens that tool. If certain bacteria consistently correlate with gold particles in needles, field teams could screen for those microbes to prioritize where to sample or drill. That means fewer blind holes, lower environmental impact, and better chances of success. The approach is not a replacement for geophysics or traditional geochemistry. It is an additional line of evidence that can make exploration more efficient and more respectful of sensitive ecosystems.

From Forest Needles to Water Treatment

The same biology that shapes metals inside needles may help clean up mining-affected waters. Aquatic plants and their microbial partners live on the front line of metal exposure in streams near mines. If biofilms and plant tissues encourage dissolved metals to precipitate into particles, engineers could harness that chemistry in treatment systems. Ongoing work is examining how metals precipitate within moss tissues and whether aquatic biofilms can help remove metals from water in a controlled, scalable way.

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Next Steps: Proving the Mechanism and Scaling the Method

To move from intriguing observations to a reliable method, researchers will need direct, time-resolved experiments that follow soluble gold into microbes and out as nanoparticles under controlled conditions. Future studies should extend beyond spruce, test other plant species over different deposit types, and track seasonal changes and groundwater routes. The goal is to tie microbial fingerprints and gold signals together in ways that field crews can use with confidence.

Looking Ahead

Plants are holobionts, living systems made of the host and its microbes. Those partnerships guide how nutrients and trace elements flow, how stress is managed, and in this case, how minerals can form inside tissues. In Finland’s boreal forests, the evidence points to microbes helping lock tiny bits of gold into solid, safe form within spruce needles. That microscopic record can point to geology underfoot and to practical tools on the surface. As the experiments progress, a clearer path emerges, from careful observation to a greener way of finding and managing metals in the real world.

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