A surprising study has shown that Christmas or spruce trees hide gold inside their needles.
Researchers have unveiled this connection between microbes in Norway spruce needles and gold nanoparticles that travel from soil, likely near deposits.
The study suggests that microbes living inside plants may influence the accumulation and solidification of gold in trees, a process known as biomineralization.
“Our results suggest that bacteria and other microbes living inside plants may influence the accumulation of gold in trees,” said Kaisa Lehosmaa, postdoctoral researcher from the University of Oulu, Finland.
The findings could lead to environmentally friendly mineral exploration and water purification.
The microbe-gold connection
This recent study offers preliminary evidence detailing the path of gold into spruce trees.
The research team collected 138 needle samples from 23 spruce trees growing near the Kittilä gold mine in Northern Finland.
Norway spruce trees accumulate gold nanoparticles by utilizing their resident, symbiotic bacteria, known as endophytes.
These endophytes, which typically aid the plant in functions like hormone production, facilitate biomineralization.
After the Norway spruce absorbs soluble gold from the soil via its roots, the resident endophytic bacteria within the tree’s tissues take action, initiating the segregation and solidification of the gold.
Once there, the tree’s internal microbes convert the soluble gold into solid, nanosized particles (gold dust).
The endophytes likely perform this conversion as a mechanism to reduce the the metal’s toxicity to both the plant and themselves.
The particles themselves are a millionth of a millimeter in size, making them unusable for commercial collection.
The metal’s nanoparticles were detected inside the needles of four trees, consistently enveloped by bacterial biofilms.
The needles with gold had a higher occurrence of certain bacterial groups, including P3OB-42, Cutibacterium, and Corynebacterium, as confirmed by DNA sequencing.
“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,” said Lehosmaa.
Implications for exploration and the environment
While the microscopic gold is too small for commercial extraction, the discovery is important for the mineral industry.
It could pave the way for the development of bio-based and environmentally friendly mineral exploration methods.
For years, geologists have used biogeochemical methods — analyzing metal traces in plants and soils — to locate deposits.
Research Professor Maarit Middleton from GTK notes, “This new research enhances our understanding of what is actually happening in the process.”
With this understanding of how bacteria facilitate the formation of the metal’s nanoparticles, scientists can potentially screen for specific microbial fingerprints in plants to locate valuable mineral deposits underground.
This could make gold exploration more efficient and environmentally friendly, reducing the need for extensive, often destructive, drilling.
The approach can also be extended to other minerals and plant species.
For instance, investigating this biomineralization process in organisms like aquatic mosses could open a parallel path toward environmental cleanup. The microbes within the mosses may be harnessed to remove metals from mining-impacted waters.
The research thus promises dual benefits for both sustainable resource discovery and ecological remediation.
The findings were published in the journal Environmental Microbiome.