Gene transcription response to weathering of K-bearing minerals by Aspergillus fumigatus

In order to determine the mechanisms by which fungi weather potassium-bearing minerals on a molecular level, we prepared differential expression cDNA libraries of Aspergillus fumigatus using suppression subtractive hybridization (SSH) technology. The specimens were cultured with and without potassium-bearing minerals. Among genes that were upregulated by the presence of these minerals, 24% were found to be involved in carbon source consumption. Of downregulated genes, 54% were found to code for membrane proteins. This study showed that the factors that could accelerate weathering of K-bearing minerals involved organic acids, carbonic acid, and redox participant molecules. K-bearing minerals were found to upregulate the expression of carbonic anhydrase (CA), implying that A. fumigatus was capable of converting CO2 into carbonate to accelerate the weathering of potassium-bearing minerals, which fixed CO2. During mineral weathering, the fungus changed its metabolism, produced more metal-binding proteins, and reduced membrane metal transporter expression, which can modulate ion absorption and disposal and promote acid production. The results of this study may improve our understanding of the mechanisms by which microorganisms weather silicate minerals. Because silicate weathering consumes CO2, the current study provides molecular evidence for the participation of microorganisms in silicate weathering and carbonate formation.

► We discuss a project that monitored gene expression in fungal weathering. ► Factors found to accelerate weathering of K-bearing minerals are shown. ► These minerals induce upregulation of the expression of carbonic anhydrase (CA). ► Results may increase understanding of fungal weathering of silicate minerals.