The biological control potential of extracellular protein from Bacillus velezensis against Ralstonia solanacearum in tomatoes.

Bacterial wilt caused by Ralstonia solanacearum seriously threatens tomato production. At present, tomato bacterial wilt control mainly relies on chemical agents, but long-term use can lead to environmental problems and resistance. Bacillus velezensis is a potential biocontrol bacterium; however, studies on its extracellular proteins related to antibacterial activity remain limited. In this study, B. velezensis TR-1 was used to identify key extracellular protein components with antagonistic activity against R. solanacearum and to evaluate their biocontrol potential. Crude extracellular proteins were obtained from the TR-1 culture supernatant by ammonium sulfate precipitation. Active components were separated using Sephadex G-75 and identified by LC-MS/MS. The results showed that serine protease was the major component of the active fraction. Meanwhile, pot experiments showed that the crude protein solution achieved a control effect of approximately 60% against tomato bacterial wilt. This study is the first to identify multiple serine proteases in the active components of the B. velezensis supernatant. Based on SEM and TEM observations and protein structure prediction, serine proteases are inferred to be involved in the inhibition of R. solanacearum, providing a new perspective for the green control of tomato bacterial wilt.