Screening of antimicrobial bacteria from Antarctic sediments and identification of antagonistic substance

Abstract:

[Background] Scientific research shows that due to the special environmental conditions in Antarctica and the abundance of microbial resources, it is expected to screen out highly effective antimicrobial microorganisms. [Objective] To isolate and screen out antimicrobial strain from Antarctic sediments and to make preliminary identification of antibacterial substance, by using the pathogen of cucumber fusarium wilt named F. equiseti as indicator fungus. [Methods] The plate-based confrontation method was used to screen the strain from sediment samples and fermentation broth, with the strongest antimicrobial effect on Fusarium equiseti. Based on morphological, physiological, biochemical, molecular biology analysis, the strain was identified. Then the antimicrobial spectrum of antimicrobial substance in the fermentation broth was studied, and the stability of the antimicrobial component was detected under different temperatures and pH conditions, and the antimicrobial substance in fermentation broth was identified by the method of ammonium sulfate precipitation. [Results] A total of 62 bacteria were isolated from the Antarctic sediment samples, and 5 were with better antiseptic effects, of which the most effective strain was identified as Bacillus subspedestion (Bacillus subtilis subsp. spizizenii) and named JYM35. The result of antimicrobial spectrum showed that JYM35 is of strong antagonistic effect on the pathogen of towel gourd fusarium wilt named F. proliferatum and pathogen of pepper fusarium wilt named Fusarium equiseti, and has antagonistic effect on brown rot of long-bean named Choanephora, and also has certain antimicrobial effect on aquatic pathogen named Vibrio parahaemolyticus and V. alginolyticus as well. The antagonistic substance contained in the fermentation broth of JYM35 has the characteristic of high thermal stability, and it is resistant to alkali but not to acid. Through ammonium sulfate precipitation, it can be preliminarily determined that the antagonistic substance belongs to proteins. [Conclusion] Strain JYM35 is a broad-spectrum antimicrobial strain that produces protein-like active substance and has the strongest antagonistic effect against fusarium wilt.