- Lapland spruce trees contain gold nanoparticles in their needles, detected in 4 of 23 sampled trees.
- Biomineralization mediated by endophytic bacteria (Cutibacterium, Corynebacterium, P3OB-42) precipitates dissolved gold.
- The quantities are tiny and unusable, but they serve as a biological footprint of underground deposits.
- The technique promotes more sustainable prospecting and suggests uses in phytoremediation of water containing metals.
In the forests of Lapland (Finland), a A team from the University of Oulu and the Geological Survey of Finland has found gold nanoparticles within the needles of the red spruce (Picea abies). The research, published in Environmental Microbiome, documents for the first time in detail the presence of the metal in plant tissue alongside endophytic microbial communities.
El The interest of this work does not lie in extracting metal from trees, but rather in understanding a less-visible biogeochemical process that could guide lower-impact subsurface exploration. According to the study, Microbes residing inside the plants precipitate the dissolved gold and convert it into solid nanometer-sized particles..
From the subsoil to the needles: this is how metal travels
Gold present underground can be found in ionic form in the waters that moisten the soil; these solutions reach the roots and are passively incorporated into the sap flow. From there, metal ions rise through the vascular system until reaching the aerial parts, including the needles.
In the vicinity of the Kittilä mine, the largest gold deposit in Europe, scientists analyzed 138 needle samples from 23 Picea abies specimens. In four trees were detected embedded gold particles inside the tissue, always in areas colonized by bacterial biofilms.
La Detection was performed with high-resolution microscopy and genetic analysisThe particles are so small that are not visible to the naked eye and its identification requires specialized instrumentation; Its size ranges from a millionth of a millimeter.
The Concentrations measured in dry leaves range from 0,2 to 2,8 micrograms per kilogram, that is, insignificant amounts from an economic point of view. The value of the find es, so, indicative and scientific: allows reading underground signals without trenching or drilling.
This metal journey is not without risks for the plant, since Gold can be toxic under certain conditionsThis is where endophytic microorganisms come into play: By modifying the local chemistry in biofilms, they promote the precipitation of dissolved gold and immobilize it as nanoparticles., reducing its harmful potential.
Key microbes and what this discovery is for
DNA analysis on the gold-plated needles showed that certain bacterial groups were significantly more prevalent in these samples. Cutibacterium, Corynebacterium and the P3OB-42 clade, whose presence is associated with the formation and stabilization of nanoparticles within plant tissue.
This behavior fits with the concept of biomineralization: biological processes that transform inorganic substances into solid forms within living organisms. In the fir trees studied, biofilms act as microreactors where gold goes from being in solution to being trapped in an elemental state.
The main practical implication is the possibility of using trees as deposit bioindicators Buried. Instead of relying on invasive surveys, leaf or needle sampling can provide clues about subsurface composition, optimizing subsequent explorations using geophysical or geochemical methods.
The idea is not new: in Australia Traces of gold had been observed in eucalyptus leaves, a precedent that already pointed to the usefulness of vegetation in prospecting. Those deep roots, capable of reaching large pockets of groundwater, They also transported metals in minimal quantities to the top, where they remained as chemical signals.
However, it should be emphasized that Not all trees accumulate gold nor do they do so in the same way.Factors such as soil type, acidity, microbiota, and seasonal conditions influence the presence and distribution of the metal. Therefore, combining biological data with mapping and geophysics increases the method's reliability.
Beyond mineral prospecting, this knowledge opens the door to phytoremediation. If microorganisms associated with plants and mosses can precipitate metals in their tissues, They could be used to remove contaminants from water affected by mine drainage or other sources of pollution., with low-cost solutions with a smaller environmental footprint.
El work signed by the University of Oulu and the GTK redefines the role of vegetation: from being mere passive recipients to becoming sentinels of the subsoil and allies to monitor resources and risksThe map of the most useful species, the most effective bacterial communities, and the best sampling scales remains to be refined.
Using the spruce trees of Lapland as a case study, Science shows that gold does not "grow" on trees, but it does leave tiny traces inside that reveal what is happening beneath our feet., offering a cleaner alternative for exploring and, where necessary, helping to restore environments affected by metals.
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