Aspergillus Niger In The Process Of Potassium Rock Weathering Related Gene Expression Regulation

Soil microorganisms are the regulators of the ecosystem as well as an important part of the soil. During the long-term process, the rocks were gradually transformed into soil minerals in which the microbial mineral weathering plays an important role. There are some factors about accelerating microbial mineral weathering including the synergy of mechanical force, secreted organic acids and extracellular polymers and direct redox reaction, etc. But the prior related researches are concentrated in the mechanisms of mineral decomposition at the cellular level and improvement of the soil fertility by using inorganic weathering products. This paper suggests that more in-depth researches should be done to reveal the molecular mechanisms of microbial mineral weathering. To look for the nature of microbial weathering and soil formation on the level of molecular biology, this paper would provide more theoretical supports to microbial ecological application and ecological technical advancement.Aspergillus niger is an important industrial fermentation strains, growth rapidly in almost every poor environment or even in organic waste. A. niger has a strong physical effect on the surface of mineral. To reveal the molecular mechanism of fungal mineral weathering, the suppression subtractive hybridization (SSH), dot blot, real-time fluorescence quantitative PCR (RT-qPCR), high-throughput sequencing and other molecular biology techniques were applied. The differential expression of mRNA of A., niger in the process of dissolving potassium-bearing minerals was studied. The specific expression of cDNA library was obtained when A. niger was cultured in K+free and potassium-bearing mineral containing medium. In the up-regulated expression genes induced by minerals, most were related to the consumption of the carbohydrate, RN A binding, structural constituent of ribosome and also protein translation; in down-regulated expression genes inhibited by minerals, most of them belong to membrane proteins. At mRNA level, this paper described that A. niger might promote the weathering of potassium-bearing minerals by secreting organic acids, utilizing carbonic acid and direct redox reaction, etc. Rich carbon source will benefit for fungal mineral weathering, because A. niger tends to provide the energy and produce more organic acids by consuming more sugar source in the process of mineral degradation. Potassium-bearing minerals can induce the expression of carbonic anhydrase, which relevant to the consume of CO2in the air. A. niger could adjust physiological metabolism to serve mineral weathering, such as expressing more metal-binding proteins and reducing the expression of several membrane transport proteins. All of these can regulate ion uptake and distribution, promoting acid producing and adapting to acid microenvironment.The paper introduced molecular analysis techniques of differential expressed mRNA and high-throughput sequencing into the studies of microbial weathering of rocks.It confirmed that potassium minerals can induce the gene expression about the weathering of potassium-bearing minerals, and revealed the role and regulation mechanism in A. niger with potassium-bearing minerals weathering initially. Results of this paper to provide a new vision to study the interaction mechanisms between fungi and rock in the biogeochemical cycling process, and also the theoretical basis that fungi play an important role in microbial weathering of potassium-bearing minerals.