Role And Mechanism Of Halophilic/salt-tolerant Microorganisms In Remediation Of Saline-alkali Soil

China is a country with a total of more than 99 million hectares of saline-alkali land,accounting for about 10% of the world's saline-alkali land.However,the lack of arable land per capita and the decline of arable land quality seriously hinder the rapid development of modern agriculture in China.Scientific restoration of salinized soil is the fundamental way to increase the cultivated land reserve,curb the spread of secondary salinization and speed up the construction of high-quality farmland in China.The soda saline-alkali land in Northeast is one of the main types of saline-alkali land in China,and it is a typical ecologically fragile area.In recent years,due to the influence of climate,water conservancy and unreasonable development,the regional ecology has deteriorated rapidly,and the spread of soil salinization in Northeast China has intensified.Through the systematic study on the microbial community of soda alkali soil in Northeast China,we found that there was a correlation between the growth and decline of fungal flora and the degree of salinization.The application of halophilic/salt tolerant fungi as the improved substrate of the core flora can effectively repair the saline alkali soil and improve the crop yield.On this basis,it is further studied the microbial diversity and dynamic changes of the growth and decline of soda saline alkali Soil in Northeast China,focused on the remediation mechanism of salt tolerant and alkali resistant Aspergillus aeruginosa CCHA in saline alkali Soil management,discussed the function and mechanism of extracellular enzyme in straw degradation.The main findings of this study are as follows:1.The application of halophilic fungi,such as Aspergillus glaucus,in the restoration of soda saline alkali Soil in Songyuan,Baicheng and Da'an of JilinProvince was studied,which proved the role of halophilic fungi in the restoration of saline alkali Soil.The combination of halophilic Aspergillus CCHA and inert materials can significantly improve the saline alkali soil.After improvement,the soil pH value,total salt content,aggregate structure and other important indicators are close to or reach the production capacity and soil indicators under normal soil conditions.After measuring the production,the rice varietie in the No.2 experimental field(Wujingzi Village,Chaganhua Town,Songyuan City)is Song geng No.3,the average yield per year is 9030kg/ha in the sixth year;The rice variety of the No.6experimental field(Fengshou Village,Da'an City)is Jida 151,the average yield per year is 6760kg/ha in the second year;The rice variety in the No.7 experimental field(Shuangmiao Village,Zhenlai County,Baicheng City)is: Tongyu 406,the average yield per year is 3920 kg/ha in the first year.2.The results showed that the species and quantity of soil microorganisms,especially fungi,decreased with the increase of soil salinity and pH.We isolated nine strains MH777421-777429 with strong salt resistance,from the saline soil in the Songnen Plain.These nine fungi can grow in 5%-20% sodium chloride medium that the most growth salinity is 5%,and the range of growth pH is wide.It is proved that fungi are important for the restoration of saline alkali soil and the growth of vegetation.3.The repair mechanism of halophilic fungi in saline alkali soil was studied by electron microscopy,enzyme activity detection and mass spectrometry:(a).The biological effect,salt tolerance and amphoteric reproduction characteristics of Aspergillus halophilus make it grow normally in the saline alkali soil.The network wraps the soil particles and improves the composition of the micro aggregate in the saline alkali soil;(b).The extracellular enzyme in the metabolite of Aspergillus halophilus degrades the straw to release organic matter efficiently and improve the soil fertility;(c).The enrichment of chloride,sodium and bicarbonate ions in the soil by Aspergillus halophilus can effectively reduce the alkalinity;(d).Salt alkali can induce the up-regulation of gene expression of organic acid synthetase in the metabolites of Aspergillus halophilus,effectively neutralize the salt alkali,balancethe pH of the saline alkali soil,and participate in the formation of soil nanoparticles;(e).The formation of nanoparticles by the metabolites of Aspergillus halophilus and metal ions in the soil can improve the structure of soil aggregates;(f).The formation of nanoparticles by the metabolites of Aspergillus halophilus The expression of reductase gene was up-regulated,and the production of reductase could promote the formation of nanoparticles.4.In order to improve the activity of halophilic fungi and increase the activity of heavy saline-alkali enzymes,the fungal cellulase and archaea enzymes with double active were mainly studied.AgCMCase cellulase can efficiently degrade straw,release organic matter,and produce nanocellulose to improve soil aggregate structure;Tk-ChiA hydrolase with double enzyme activity,strong heat resistance and high biological activity can degradate chitin and straw efficiently,product energy substances and biomass fertilizer to improve soil fertility of saline-alkali soil.In conclusion,it is found that there is a correlation between the growth and decline of fungal flora and the degree of soil salinization;the research focuses on the repair mechanism of halophilic fungi in the process of saline alkali Soil management,which provides a theoretical basis for the effective use of halophilic / salt tolerant fungal agents to repair saline alkali Soil;the cellulase of CCHA and a kind of bioactive cellulase of marine archaea KOD1 are studied The results show that soil enzymes play an important role in the restoration and improvement of soil fertility.The results of this study provide a new strategy and theoretical reference for the future saline alkali Soil restoration and soil fertility improvement.