Screening Of Saline-alkali-tolerant Microorganisms And Improvement Test Of Saline Soil

China has a large area of saline-alkali land.Land salinization seriously restricts the development of agriculture,forestry and animal husbandry economy and threatens the ecological security of our country.Therefore,it is of great ecological and economic significance to study and develop an efficient method for saline soil treatment.Soil functional microorganisms have great application potential in saline soil remediation and improvement.In this thesis,three strains of bacteria were screened from saline-alkali soil from a mining area in Inner Mongolia.Through genome sequencing,it was found that genes such as bet B and mnh B were related to the adaptability of bacteria to high salt and high permeability environment.Single factor experiments were set up to study the growth of each strain in different environments and its effects on salt and p H in the environment,and the biochemical characteristics of each strain were analyzed and evaluated.Pot experiment was set up to study the improvement effect of the target strain combined with plants on saline soil.The changes of soil physical and chemical properties were used as evaluation indexes,and the function of soil microbial community was used to explain the relevant mechanism.The main research results are as follows:(1)The three microorganisms were identified as Bacillus pumilus,Pseudomonas nitrogenides and Bacillus subtilis.Through genome sequencing,it was found that Bacillus pumilus has gbs B,bet B,mnh B and other genes related to high salt and high permeability environmental adaptability.Other genes related to bacterial perception and adaptation to environmental osmotic pressure and environmental acid-base,such as Kin B and com A/P,were also found.Pseudomonas nitrogenides has bet B and mnh B genes.Bet B is used for biosynthesis of osmotic protective agent glycine betaine to resist high salt osmotic environment.(2)Bacillus pumilus was cultured under the condition of salt content of 30g/L and p H=9.After 7 days,the p H of culture medium decreased by 0.79 and the salt content decreased by 23.94%.Pseudomonas nitrogenides had strong salt tolerance,and its fitting degree of its growth curve with Bi Dose Resp model was 0.9994.The optimum Na Cl concentration of the culture medium was about 20-30 g/L.Under the condition of 30g/L salt content and p H=9 for 4 days,the p H of culture medium decreased by 1.09 and the salt content decreased by 30.47%.Bacillus subtilis can effectively reduce the p H value of the culture medium.Its growth curve was in good agreement with the Logistic model.(3)Bacillus pumilus was applied to saline soil.After 20 days,the soil p H decreased by 0.58 compared with the initial,and the soil chloride ion content decreased by 31.27%compared with the initial.After 50 days,the soil p H decreased by 0.39 compared with the initial value.The salt content decreased by 27.4%compared with the initial value,and the soil chloride ion content decreased by 51.69%compared with the initial value.Compared with the control group,the application of Pseudomonas nitrogenides can effectively reduce soil alkalinity,increase soil available nutrients and organic matter content,and have a better improvement effect on saline soil.In the 50-day soil microbial community,Bacillus became the dominant genus in each community.The functional abundance of COG3067(Na~+/H~+antiporter,corresponding functional gene mnh B)and COG4175(osmoprotectant glycine betaine,corresponding to functional genes gbs B and bet B)in group S and group Z was significantly higher than that in control.The thesis contains 56 pictures,28 tables and 126 references.