Fungal Iron Biomineralization in Río Tinto

Abstract

Abstract:Although there are many studies on biomineralization processes, most of them focus on the role of prokaryotes. As fungi play an important role in different geological and biogeochemical processes, it was considered of interest to evaluate their role in a natural extreme acidic environment, Río Tinto, which has a high level of fungal diversity and a high concentration of metals. In this work we report, for the first time, the generation of iron oxyhydroxide minerals by the fungal community in a specific location of the Tinto basin. Using Transmission Electron Microscopy (TEM) and High Angle Angular Dark Field coupled with Scanning Transmission Electron Microscopy (HAADF-STEM) and Energy-Dispersive X-ray Spectroscopy (EDX), we observed fungal structures involved in the formation of iron oxyhydroxide minerals in mineralized sediment samples from the Río Tinto basin. Although Río Tinto waters are supersaturated in these minerals, they do not precipitate due to their slow precipitation kinetics. The presence of fungi, which simply provide charged surfaces for metal binding, favors the precipitation of Fe oxyhydroxides by overcoming these kinetic barriers. These results prove that the fungal community of Río Tinto participates very actively in the geochemical processes that take place there.

Ultra-small microorganisms in the polyextreme conditions of the Dallol volcano, Northern Afar, Ethiopia

“…The cellular morphologies were associated with the needle-shaped crystals (Fig. 6M), which suggests a relationship between the microorganisms and the biomineralization process as has been previously reported in other acidic environments 17 .…”

Biologically mediated weathering in modern cryptogamic ground covers and the early Paleozoic fossil record

“…4 b). This is consistent with hyphal exudates promoting the production of Fe-rich bio-precipitates (e.g., Figs 2 h & 4 e), which is well documented and supported in the literature; occurrences include the fungal biomineralization of iron oxyhydroxide minerals (Oggerin et al 2016), fungal and bacterial slime biomineralization of Mn oxides (Akhtar & Kelso 1992), and bio-precipitation of Fe, Mn and Zn by fungal oxalic acid exudates (Gadd 1999). We propose that Fe accumulation documented here can be used as a biomarker for biologically-mediated weathering (particularly by fungi) in the fossil record.…”

Correlative Microscopy: a tool for understanding soil weathering in modern analogues of early terrestrial biospheres

“…Their existence is further supported by the presence of Fe-rich nodules in both types of tunnel (Figs 4gm). Fe-rich nodules are thought to be indicators of fungal hyphae bio-precipitation in modern CGCs 18 , with further occurrences reportedly created by lichens 52,53 , bacteria 43 , other fungi [54][55][56] , and iron oxidising bacteria 57 . The Fe concentration of the nodules is higher than in the feldspathic and Mg-Fe silicate phases of the grain (Fig.…”