Lian,B., Wang,B., Pan,M., Liu,C. and Teng,H.H.(2008): Microbial release of potassium from K-bearing minerals by thermophilic fungus Aspergillus fumigatus. Geochimica et Cosmochimica Acta, 72, 87-98.

『高温性菌類アスペルギルス・フミガタスによるK含有鉱物からのカリウムの微生物的放出』

『Abstract
　A strain of thermophilic fungus Aspergillus fumigatus was cultured with K-bearing minerals to determine if microbe-mineral interactions enhance the release of mineralic potassium. Experiments were carried out in two settings, one with the mineral grains and the fungal cells in direct contact, and the other employing a membrane (pore size 0.22μm) to separate the two. Measurements over a period of 30 days showed that, irrespective of the experimental setup, the concentration of free K in the culture was drastically higher than those in any of the control experiments where no living organism was present. Moreover the occurrence of mineral-cell physical contact enhanced potassium release by an additional factor of 3 to 4 in comparison to the separation experiments. For contact experiments, Electron Probe Microanalysis revealed the formation of mycelium-mineral aggregates, and Atomic Force Microscopy imaging further indicated the possible ingestion of mineral particles by the fungus cells. Contrasting to what was observed and expected in control experiments, the potassium solubilization rate showed a positive dependence upon pH when fungi and minerals were mixed directly, and exhibited no correlations with solution acidity if cell-rock contact was restrained. These results appear to suggest that A. fumigatus promoted potassium release by means of at least three likely routes, one through the complexation of soluble organic ligands, another appealing to the immobile biopolymers such as the insoluble components of secretion, and the third related to the mechanical forces in association with the direct physical contact between cells and mineral particles.

Keywords: Microbe-mineral interaction; Mineral weathering and dissolution; Thermophilic fungus; Aspergillus fumigatus; K-feldspar; Illite; Potassium solubilization and release』

1. Introduction
2. Materials and methods
　2.1. Isolation, selection, and identification of fungal species
　2.2. Mineral phases
　2.3. Experimental settings for microbe-mineral interactions
　2.4. Experimental sample analysis
3. Experimental results
　3.1. Release of K during fungus-rock interactions
　3.2. Formation of mycelium-mineral aggregates
4. Discussion
　4.1. Dependence of K solubilization kinetics upon H and time
　4.2. Importance and implications of the fungus-mineral physical interactions
5. Conclusions
Acknowledgments
References


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