Purification and Identification of an Antimicrobial Protein from Bacillus stercoris TY-12 and Its Biocontrol Functions Against Ralstonia solanacearum

Abstract

Ralstonia solanacearum is a bacterial pathogen that causes bacterial wilt in plants, resulting in significant economic losses worldwide. Biological control that mainly utilizes Bacillus spp. is one of the most effective methods to prevent this disease. In this work, a strain of Bacillus stercoris TY-12 with an obvious antagonism effect on R. solanacearum was screened, and the inhibition diameter against R. solanacearum reached 2.18 cm by the plate antagonism test. Furthermore, an antimicrobial protein was isolated and purified from the fermentation supernatant of TY-12. The LC-MS/MS analysis results indicated that the purified antimicrobial protein is a member of the M42 family metallopeptidase with a molecular weight of approximately 40 kDa and named MP-TY12. After co-culture with MP-TY12 for 4 h, the cell surface of R. solanacearum was disrupted under SEM, indicating that MP-TY12 may inhibit R. solanacearum growth by enzymatically cleaving peptide bonds within the cell wall or membrane structure via hydrolysis. To evaluate the potential application of TY-12 in disease control during crop production, the biocontrol efficacy of TY-12 on the capsicum infected by R. solanacearum was investigated and achieved 84.18%. The growth promotion tests showed that the dry weight, fresh weight, stem diameter, stem length, root length, and the chlorophyll content of capsicum using TY-12 was obviously increased compared to the blank control. It is suggested that TY-12 could be used as a new biocontrol microbial strain in crop production and MP-TY12 might be developed as an antimicrobial agent.