Spruce Needle Bacteria Aid in Gold Nanoparticle Formation

A remarkable instance of synergy between the plant kingdom and microbial life, specifically concerning the accumulation of precious metals, has been uncovered by Finnish scientists. These researchers documented that bacteria residing within the needles of the Norway spruce (Picea abies) play an active role in the creation of gold nanoparticles. This groundbreaking finding, detailed in the scientific journal BMC Microbiology, necessitates a reassessment of the established understanding regarding the complex interplay among subterranean deposits, local flora, and microorganisms.

The investigative team, comprising experts from the University of Oulu and the Geological Survey of Finland, undertook a rigorous analysis. They collected 138 needle samples sourced from 23 spruce trees growing near the Kittilä mine, which stands as Europe’s largest gold mining operation. Microscopic gold particles were identified within the bacterial biofilms present in the samples taken from four of these trees. Subsequent DNA analysis of these "gold-bearing" specimens revealed a dominance of specific microbial genera, notably Cutibacterium and Corynebacterium.

The established mechanism operates as follows: soluble gold ions, leached from deep underground reserves, are absorbed through the roots and subsequently transported up into the spruce needles. Once there, the activity of endophytic bacteria causes the dissolved substance to precipitate, converting it back into a solid state and forming nanoparticles measuring just a few nanometers in size. While the quantity of this naturally occurring "harvest" holds no commercial value, the mechanism itself unlocks new possibilities for geological exploration and prospecting. This phenomenon, termed biomineralization, has been documented previously—for example, in the leaves of Australian eucalyptus trees. However, this study marks the first time a direct correlation has been established with a stable, permanent microbial community residing entirely within the host plant.

Gaining insight into this natural process could serve as a catalyst for developing environmentally sound methodologies for locating valuable resources, advocating for a more sustainable approach to subsurface exploration. Furthermore, related processes have long been leveraged by industry on a massive scale. Bacterial leaching technology relies on the capacity of specific microorganisms to oxidize sulfides, thereby accelerating the release of gold from refractory ores. For instance, the USSR launched its inaugural pilot plant for biohydrometallurgical processing in 1974. Today, comparable techniques are employed globally, such as at the Olympiadinskoye deposit, to successfully extract metal encased within sulfide matrices.