AUTHOR=Fan Haiyan , Zhang Zhanwei , Li Yan , Zhang Xun , Duan Yongming , Wang Qi 

TITLE=Biocontrol of Bacterial Fruit Blotch by Bacillus subtilis 9407 via Surfactin-Mediated Antibacterial Activity and Colonization

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.01973

DOI=10.3389/fmicb.2017.01973

ISSN=1664-302X

ABSTRACT=<p>In this study, <italic>Bacillus subtilis</italic> 9407 showed a strong antibacterial activity against <italic>Acidovorax citrulli in vitro</italic> and 61.7% biocontrol efficacy on melon seedlings 4 days post inoculation under greenhouse conditions. To understand the biocontrol mechanism of <italic>B. subtilis</italic> 9407, identify the primary antibacterial compound and determine its role in controlling bacterial fruit blotch (BFB), a <italic>srfAB</italic> deletion mutant (Δ<italic>srfAB</italic>) was constructed. The Δ<italic>srfAB</italic> which was deficient in production of surfactin, not only showed almost no ability to inhibit growth of <italic>A. citrulli</italic> but also decreased biofilm formation and reduced swarming motility. Colonization assay demonstrated that <italic>B. subtilis</italic> 9407 could conlonize on melon roots and leaves in a large population, while Δ<italic>srfAB</italic> showed a four- to ten-fold reduction in colonization of melon roots and leaves. Furthermore, a biocontrol assay showed that Δ<italic>srfAB</italic> lost the biocontrol efficacy. In summary, our results indicated that surfactin, which consists of C13- to C16-surfactin A was the primary antibacterial compound of <italic>B. subtilis</italic> 9407, and it played a major role in biofilm formation, swarming motility, colonization and suppressing BFB. We propose that the biocontrol activity of <italic>B. subtilis</italic> 9407 is the results of the coordinated action of surfactin-mediated antibacterial activity and colonization. This study reveals for the first time that the use of a <italic>B. subtilis</italic> strain as a potential biological control agent could efficiently control BFB by producing surfactin.</p>