Microbial Enzymes Involved In The Weathering Of Silicate Minerals

Silicate minerals are the main rock-forming minerals and main components of soil.The weathering of silicate minerals is directly related to the geochemical cycle and utilization of elements,the formation and evolution of secondary minerals and soil,as well as the CO2 cycle and global climate change.The interaction of microorganisms with silicate minerals is commom in earth.Microorganisms acquire necessary mineralelements to survive.Microorganisms accelerating mineral-weather results from several factors,such as the synergy of mechanical force,direct redox reaction,secreted several acidic metabolites,elongated hypha biomechanical role and,etc.The prior researches are focused on the mechanisms of mineral weathering at the cellular level,which limits the further development of mineral weathering.With the rapid development of molecular biology technology,provided that the nature of microbial weathering minerals at the molecular biology level could be found,this would help provide further theoretical and technical support for the microbial-mineral application of agriculture and industrial development.Aspergillus niger is an important industrial fermentation strains,grows rapidly in almost poor environment.In our previous study,the expression of Na,K-ATPase ?1 subunits(NKA ?1)and carbonic anhydrase(CA)of A.niger were significantly up-regulated in the absence of soluble potassium(with potassium silicate minerals),suggesting that they may be related to biological weathering.So,this paper will use molecular biology technology to genetical modify A.niger,to construct a strain of CA overexpressed(oeCA),a knockout mutant(delCA),a mutant of NKA?1 overexpressed(oeNa),and then do research about bio weather of these strains on potassium feldspar,biotite,serpentine and wollastonite.The main results are as follows:1)The expression of carbonic anhydrase gene of CA over-expressed A.niger(oeCA)is up-regulated,and 55.9 times that of the wild-type A.niger.Carbonic anhydrase activity is not detected in CA-knockout mutant(delCA).The enzyme activity of the CA-complement strain(bCA)is the same as wild-type strain.Compared with the wild-type A.niger,the genetical modification fungus(oeCA and delCA)have better effect on weathering silicate mineral(potassium feldspar,biotite and wollastonite)and promoting the release of mineral elements.And the knockout mutant(delCA)plays a better role on promotion the dissolution of potassium feldspar,biotite and wollastonite,than the CA over-expressed strain.2)Compared that of the wild-type A.niger,the gene expression of the Na,KATPase ?1 gene over-expressed mutant(oeNa)increases 131 times and the enzyme activity of Na,K-ATPase increased 1.25 times.And the over-expressed mutant(oeNa)could promote the weather of potassium feldspar,serpentine and wollastonite,to release more metal cations(potassium,magnesium,calcium).NKA ?1 gene is closely related to the weather of silicalate minerals,and the gene expression is increased,which could enhance the ability of the strain on the weather of silicate minerals.This study proves that carbonic anhydrase gene,Na,K-ATPase ?1 gene of Aspergillus niger are involved in the weathering process of silicate minerals,which enriches the theory on the weather of silicate minerals,provides a new way to solve the difficult problem in releasing silicates mineral elements,and is of great academic value.