Breeding Nitrogen-fixing Bacteria From The Potassium Mine Of Jishou

As a big country in agricultural production, grain production should consume a large amount of industrial nitrogen fertilizer each year, it will cause decline in the quality of agricultural products, soil compaction, water eutrophication, increase the economic costs of production and other issues, however the microbial compound fertilizer can solve these problems, therefore, it has great significance to research the highly efficient microbial nitrogen fixation strains for the development of microbial compound fertilizer and agricultural sustainable development.In order to get the highly efficient nitrogen-fixing bacteria, which were isolated from the potassium mine region of Jishou, then twenty-eight strains of nitrogen-fixing bacteria were isolated from the soil samples. Nitrogen-fixing bacteria were identified by morphology, physiology and biochemical characteristics, and molecular biology based on 16 S r RNA gene sequences. Twenty-eight strains of nitrogen-fixing bacteria were isolates, belonging to eight families and ten genera, eleven strains belong to Rhizobium and six stains belong to Bacillus, Rhizobium were the dominant species. Selecting the strains grew well from each genus as a representative strain, we found that the nitrogen fixation activity of each representative strain was different after fermentation and Kjeldahl nitrogen method. The high nitrogen-fixing ability of representative strains were Rhizabium and Bacillus, among them, representative strain L13 of Rhizabium of96 h fermentation nitrogen content is 10.71 mg/L, representative strain L10 of Bacillus then followed.To find out the growth characteristics of L13 and L10, a comparative study on temperature, PH, osmotic pressure and carbon sources between the L13 and L10. The result showed that L10 and L13 had big difference in each period of growth and propagation, the lag period and logarithmic phase of L13 were shorter than L10, but the steady period of L13 was longer than L10, it could be considered that the rate of growth and reproduction of L13 was greater than that of L10, and it was the same as the environmental stressors.To make further improvement on highly effective strains of nitrogen-fixing bacteria have obtained by screeding, and the strain L13 was mutated by UV radiation and NTG to get lots of mutant strains and amutant strain L-Z1, L-Y3, which nitrogen fixation activity were increased by 84% and 89% respectively compared with the original strain L13.