The Impact Of LuxS On The Biofilm Formation And Capability Of Controlling Bacterial Wilt Of Paenibacillus Polymyxa HY96-2

Microbial pesticide produced by Paenibacillus polymyxa HY96-2 can effectively control bacterial wilt in the field,but its biocontrol mechanism needed further study.The biocontrol agents colonized at the roots of the host plants stably with biofilm which promotes the biocontrol efficiency of microbial pesticides.In addition,the quorum sensing(QS)can regulate the biofilm formation.This study aimed to investigate the effects of luxS(a key gene of AI-2 QS)on the biofilm formation and biocontrol efficiency against Ralstonia solanacearum by P.polymyxa HY96-2.We constructed a luxS knockout mutant,a luxS complement mutant and a luxS overexpression mutant.The phylogenetic tree of LuxS protein showed that P.polymyxa HY96-2 LuxS protein has high homology with LuxS protein of other probiotics,and the activity of P.polymyxa HY96-2 LuxS protein in inducing AI-2 synthesis was verified.An assay for biofilm formation in vitro and in vivo showed that the luxS positively regulated the biofilm formation by P.polymyxa HY96-2.The results of pot experiment showed that the biocontrol efficiency of the luxS-deficient strain was the lowest during the whole stage of tomato bacterial wilt with 50.70±1.39%in the late stage.The luxS overexpressing strain had the highest biocontrol efficiency during the whole stage with 75.66±1.94%in the late stage.And the complement of luxS could restore the biocontrol efficiency during the whole stage with 69.84±1.09%in the late stage that was higher than the wild strain with 65.94±2.73%.This indicated that luxS promoted the biocontrol efficiency against R.solanacearum by P.polymyxa HY96-2.Therefore,we inferred that luxS can promote the biofilm formation by P.polymyxa HY96-2,and further promoted its biocontrol efficiency against R.solanacearum.In addition,P.polymyxa HY96-2 could induce the resistance of tomato plants to bacterial wilt by JA/ET and SA in the first two days.