Characterization Of Corn Lectin And Application To Screen Of Growth-promoting Bacteria From Corn Rhizosphere

Plant Lectin is defined as a kind of sugar-protein which is composed of at least one uncatalysed region binded reversibly to a specific mono- or oligosaccharide. Different lectin was able to identify specially relative microorganisms due to its unique sugar-binding activity.Nitrogen-fixation bacteria, phosphate-releasing bacteria and potassium-releasing bacteria had been isolated from corn rhizosphere by Ashby medium, phosphate-releasing bacteria medium and potassium-releasing bacteria medium, respectively. All strains were re-screened by corn lectin 1abeled with fluorescein isothiocyanate.As a result,4 affinity strains were obtained and identified from cell and colony shape, physiological characters and 16S rDNA.Corn Lectin was extracted from corn seed powder by PBS buffer solution, prcipitated with (NH4)2SO4, purified through Sepharose 4B and lyophilized. The extraction rate of Corn Lectin was 0.154mg?g. The purified Corn Lectin was labeled with FITC by Marshall's method and the agglutinating titre was 1:16.This paper had studied the characterization of Corn Lectin in the following 4 aspects: (1) The corn lectin displayed the maximum agglutination activity with erythrocytes of rabbit but no agglutinating activity with A, B, AB, O types of human blood. (2) The lectin showed a low tolerance to heat treatment. It was stable at below 40℃. The agglutinating activity was a little lower at 50℃, but totally lost at above 60℃for 10 min. (3) The agglutinating activity of corn lectin would be showed at pH 3.0-10.0, and more potent at pH 8.0-9.0. Therefore, its lectin activity was inactivity at pH above 10.0. (4) EDTA, K+, Ca2+, Mg2+ had no effect on the agglutinating activity of corn lectin, whereas its agglutinating activity could be inhibited by Fe3+, Mn2+. The agglutinating titre was remain 1:16 after labeled by FITC by Marshall's method. In the experiment 15 strains of nitrogen-fixation bacteria, 30 strains of phosphate-releasing bacteria and 26 strains of potassium-releasing bacteria were isolated from corn rhizosphere. All strains were re-screened by corn lectin 1abeled with FITC.As a result,4 affinity strains were obtained, including 1 strain of nitrogen-fixation bacteria, named as N12; 2 strains of phosphate-releasing bacteria, named as P07, P23; 1 strain of potassium-releasing bacteria, named as K19. These strains were belong to Azotobacter, Bacillus, Pseudomonas and Bacillus, respectively.With the development of modern agriculture, excessive chemical fertilizer leads to lots of serious problems such as soil deterioration, environmental pollution and so on. Microbial fertilizer is high-efficient, low-cost and non-pollution. In this paper, the affinity strains were selected by corn lectin labeled with FITC. All these strains can be used as the original strains of microbial fertilizer especially for corn.Therefore, the development of microbial fertilizer which can reduce the amout of chemical fertilizer could solve the problems of environmental pollution and eventually benefit the quality of produce and environment.