1. Antibiosis

Antibiosis refers to the inhibitory effect of anti microorganisms on the growth and metabolism of pathogenic microorganisms by producing metabolites at low concentration, so as to affect the survival and activities of pathogenic microorganisms. For nearly half a century, a variety of effective antibacterial substances have been isolated and purified from the metabolites of different strains of Bacillus subtilis.

2. Bacteriolysis

The bacteriolytic effect of Bacillus subtilis is mainly manifested in that it adsorbs on the mycelium of pathogenic bacteria and grows with the growth of mycelium, and then produces bacteriolytic substances, resulting in the leakage of protoplasm and the rupture of mycelium; Or produce antibacterial substances to inhibit spore germination by dissolving the cell wall or cell membrane of pathogen spores, resulting in cell wall perforation and deformity.

3. Inducing plant resistance and promoting plant growth

Among them, Bacillus subtilis has the strongest stress resistance, the most functions, the widest adaptability and the most stable effect. Bacillus subtilis can produce substances similar to cytokinin and plant growth hormone, promote plant growth and make plants resist the invasion of pathogens.

4. Protect the environment

Bacillus subtilis is widely used in biological fertilizer. When used in crops or soil, it can colonize in the rhizosphere or body of crops and play a specific fertilizer effect. At present, microbial fertilizer is improving soil fertility, improving the utilization rate of chemical fertilizer, inhibiting the absorption of nitrate nitrogen, heavy metals and pesticides by crops, purifying and repairing soil, reducing the occurrence of crop diseases, and promoting the mature utilization of crop straw and municipal waste. It has played an irreplaceable role in improving the quality of crop products and food safety.

5. Adsorption and biodegradation of phenanthrene and benzopyrene in soil by Bacillus subtilis

The water environment connected with the soil is called soil water environment system, in which there are a large number of soil inherent microorganisms and biofilm on the surface. Because the biofilm forms an isolation layer, organic pollutants must first reach and pass through the isolation layer before contacting the solid substrate supporting the biofilm, which strongly changes the adsorption behavior of mineral particles or substrate, It has an important effect on adsorption.

The results showed that both phenanthrene and benzopyrene could be adsorbed or biodegraded by Bacillus subtilis. When the concentration of PAHs in liquid phase reached equilibrium within 48 hours, the microorganisms eliminated 98% of phenanthrene and 85% of benzopyrene. The 48 h adsorption isotherms of inoculated samples were linear, which could well accord with the linear equation.

6. Effect of Bacillus subtilis on respiration intensity of soil microorganisms

As one of the indicators of soil biological activity, soil respiration intensity can reflect the transformation and supply capacity of soil nutrients to a certain extent. Its change and direction of respiration rate also reflect the sensitivity and response mode of ecosystem to stress. It is an important indicator of environmental safety assessment. When the soil is polluted by foreign pollutants, Microorganisms may need more energy to maintain their survival, which makes the metabolic activity of soil microorganisms respond to varying degrees.

7. Effect of Bacillus subtilis on soil urease activity

Using soil enzymes as monitoring indicators to evaluate the ecotoxicological effects of pesticides has become one of the research hotspots in the field of environmental science. Urease is a kind of hydrolase which has been deeply studied in soil. It is the only enzyme that has a significant impact on the transformation of urea in soil and the utilization rate of urea.

After urea is applied to the soil, it is rapidly decomposed into carbon dioxide and ammonia under the catalysis of urease. Therefore, the reduction of soil urease activity can not only slow down the hydrolysis of urea and make its hydrolysates more adsorbed by the soil, effectively reduce the volatilization loss of ammonia from urea hydrolysate, but also reduce the nitrification potential of NH hydrolysate accordingly.

8. Improvement of saline alkali land by Bacillus subtilis

The harm of salt accumulation in soil, such as viscous soil structure, poor aeration, high bulk density, rising soil temperature, poor aerobic microbial activity, slow nutrient release, low permeability coefficient and strong capillarity, leads to the further intensification of surface soil salinization and the appearance of soil cold, hard and plate. Generally speaking, when the cumulative accumulation of water-soluble salts in the soil surface or sub surface layer exceeds 0.1%, or the alkalinity of the soil alkalization layer exceeds 5%, it belongs to saline soil.