Antibacterial Activity And Mechanism Of Banboo Tar On Phytopathogenic Bacterium

In this thesis, the inhibitory activities of banboo tar on 7 plant pathogenic bacterium were bioassayed by bacteriostatic circle. The results showed that 10 mg·mL^-1 banboo tar could have obviously inhibited Pseudomonas syingae pv. tomato, Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicola, Xanthomonas axonopodis pv. citri, Ralstonia solanacearum, Xanthomonas campestris pv. campestris and Pseudomonas syingae pv. lachrymans. The toxicity of the banboo tar on 7 bacterium were determined. The results showed that the EC₅₀ and EC₉₀ of banboo tar on the tested bacterium were 29²04μg·mL^-1 and 68⁶11μg·mL^-1,respectively. The banboo tar has the strongest toxicity on Pseudomonas syingae pv. tomato(EC₅₀=29μg·mL^-1 ) and the lowest toxicity on Xanthomonas oryzae pv. oryzicola (EC₅₀=204μg·mL^-1).The study of inhibitory effect of banboo tar on the population growth of P. syingae pv. Tomato showed that under the dosage of 75μg·mL^-1 and 125μg·mL^-1 of banboo tar, the lag phase of bacteria was extended and the number of cells was lower than the control at the logarithmic phase. The results suggested that the banboo tar could inhibit bacterial reproduction rate of the bacteria.Effect of banboo tar on the cell's membrane permeability of P. syingae pv. Tomato was determined. The result showed that the dosage of 75μg·mL^-1 and 125μg·mL^-1 of banboo tar could increase the leakage amount of electrolytes and proteins from the cells. So the banboo tar was able to destroy the permeability of the bacterial membranes. When the dosage of banboo tar was 125μg·mL^-1, it could induce the respiratory chain dehydrogenases into inactive state and inhibit oxygen respiration of P. syingae pv. tomato. This results suggested that banboo tar could suppress the respiration of bacteria.In conclusion, the combined results suggested that banboo tar may damage the structure of bacterial cell membrane and depress the activity of some enzymes of membranous and respiratory chain dehydrogenases,which let the bacteria population growth of Pseudomonas syingae pv. Tomato were inhibited.