The impact of Paenibacillus polymyxa HY96-2 luxS on biofilm formation and control of tomato bacterial wilt

Jincui Yi,Jingjing Tan,Yuanchan Luo,Yuejuan Cheng,Daojing Zhang

doi:10.1007/s00253-019-10162-0

Abstract

The focus of this study was to investigate the effects of luxS, a key regulatory gene of the autoinducer-2 (AI-2) quorum sensing (QS) system, on the biofilm formation and biocontrol efficacy against Ralstonia solanacearum by Paenibacillus polymyxa HY96-2. luxS mutants were constructed and assayed for biofilm formation of the wild-type (WT) strain and luxS mutants of P. polymyxa HY96-2 in vitro and in vivo. The results showed that luxS positively regulated the biofilm formation of HY96-2. Greenhouse experiments of tomato bacterial wilt found that from the early stage to late stage postinoculation, the biocontrol efficacy of the luxS deletion strain was the lowest with 50.70 ± 1.39% in the late stage. However, the luxS overexpression strain had the highest biocontrol efficacy with 75.66 ± 1.94% in the late stage. The complementation of luxS could restore the biocontrol efficacy of the luxS deletion strain with 69.84 ± 1.09% in the late stage, which was higher than that of the WT strain with 65.94 ± 2.73%. Therefore, we deduced that luxS could promote the biofilm formation of P. polymyxa HY96-2 and further promoted its biocontrol efficacy against R. solanacearum.

Highlights

With the enhancement of people’s awareness of environmental protection and food safety, microbial pesticides have attracted more and more attention due to their non-toxicity, environmental friendliness, and safety toward humans and animals (Berg 2009)
It has been reported that the luxS gene, which is a key regulatory gene of the AI-2-mediated quorum sensing (QS) system, affected the biomass and morphology of biofilms formed by some bacterial species
LuxS expression positively regulated their biofilm formation. These species (Table 1) included Gram-negative human pathogens Haemophilus influenzae (Armbruster et al 2009) and Capnocytophaga ochracea (Hosohama-Saito et al 2016), Gram-positive human pathogens S. mutans (Yoshida et al 2005) and S. pneumoniae (Vidal et al 2011), Gram-positive animal pathogens Streptococcus suis (Wang et al 2011), and Gram-positive human probiotics B. longum (Sun et al 2014), Bifidobacterium breve (Christiaen et al 2014), and B. subtilis, which is a contaminant bacterium in the dairy industry (Duanis-Assaf et al 2015)

Summary

Introduction

With the enhancement of people’s awareness of environmental protection and food safety, microbial pesticides have attracted more and more attention due to their non-toxicity, environmental friendliness, and safety toward humans and animals (Berg 2009). The microbial pesticide industry has become a “sunrise industry” in China in line with the Chinese government’s policy of “two reductions,” a policy that is focused on reducing the amounts of chemical pesticides and fertilizers used (Luo et al 2018). Jincui Yi and Daojing Zhang contributed to this work. Jincui Yi and Daojing Zhang are co-first author. Paenibacillus polymyxa HY96-2, which was isolated from the rhizosphere of tomato plants in the suburbs of Nanchang, Jiangxi Province, China, is a Gram-positive bacterium that has been shown to control a variety of plant diseases and promote plant growth (Fan et al 2012; Luo et al 2018; Xu et al 2006b). As much as 1 billion CFU/g wettable powder of

Methods

Results

Conclusion