When Burl Ives sang “Silver and gold ornaments on every Christmas tree” in “Rudolph the Red-Nosed Reindeer,” he surely didn’t know that Christmas trees contained gold inside their needles – but that’s exactly what new research has discovered.
A study published on August 28 in the journal Environmental microbiome reports that Norway spruces (Picea abies) concentrate the gold nanoparticles with the help of their resident bacteria.
These resident bacteria are known as endophytes – symbiotic microorganisms that facilitate, among other functions, hormone production and nutrient absorption. In spruce trees, these bacteria segregate soluble gold particles that the trees absorb from water through their roots.
The process is a form of biomineralization, in which living things control the formation of minerals in their tissues through a wide range of processes. In this case, the endophytes probably concentrated the particles to reduce their toxicity.
Striking gold
For this study, the researchers studied spruce trees near the Kittilä mine in northern Finland, Europe’s largest gold producer. The researchers examined 138 needle samples from 23 spruce trees. The needles of four of the trees contained gold nanoparticles.
The nanoparticles were surrounded by biofilms created by bacterial genera such as P3OB-42, Cutibacteria And Corynebacterium. These films are polysaccharides (complex sugars) and protein compounds secreted by bacteria which allow them to persist within plant tissues.
The close association between nanoparticles and bacterial biofilms indicated that bacteria were likely responsible for the isolation of the mineral. Bacterial species diversity was lower in gold-containing needles; other studies Plants with high concentrations of metals in their tissues also saw a decrease in microbial biodiversity.
No one will make a fortune cutting down spruce trees to distill the tiny amounts of gold contained in their needles – the particles measure only a millionth of a millimeter. However, trees’ absorption of the valuable mineral can be a useful indicator of gold deposits beneath the surface.
“Screening for these bacteria in plant leaves could make gold exploration easier,” Lehosmaa said.
