Surfactin triggers biofilm formation of Bacillus subtilis in melon phylloplane and contributes to the biocontrol activity

Abstract

The biocontrol activity of many Bacillus species has been traditionally related to the direct antagonism of pathogens. In previous works, we reported that B. subtilis strain UMAF6614 was an efficient biocontrol agent that produced bacillomycin, fengycin and surfactin lipopeptides. Bacillomycins and fengycins were shown to have antagonistic activity towards fungal and bacterial pathogens of cucurbits; however, the functionality of surfactin remained unclear. In this study, the role of surfactin in the biocontrol activity of this strain was investigated. We observed that a deficiency in surfactin production led to a partial reduction of disease suppression by this biocontrol agent, which coincided with a defect in biofilm formation and the colonization of the melon phylloplane. These effects were due to a dramatic reduction in the production of exopolysaccharide and the TasA protein, which are the two major components of the extracellular matrix. We propose that the biocontrol activity of this strain is the result of the coordinated action of the three families of lipopeptides. B. subtilis UMAF6614 produces surfactin to trigger biofilm formation on melon phylloplane, which ensures the long-term persistence and the adequate secretion of suppressive lipopeptides, bacillomycins and fengycins, which efficiently target pathogens.

Improvement of Antagonistic Activity of Bacillus megaterium MHT6 against Fusarium moniliforme using He-Ne Laser Irradiation

“…Poor root colonization by biocontrol agent may result in low biocontrol ability. The surfactin deficient mutant derived from the wild strain significantly decreased colonization ability on the plant and then reduced the biocontrol ability against pathogen infection (Zeriouh et al, 2014). The result of strain motility assays indicates the mutant MHT88 exhibited higher motility than wild strain MHT6.…”

“…As it was shown in the results the mutant MHT88 is capable of spreading from the site of inoculation. Bacteria facilitate their growth and survival by forming cooperative and multicellular communities, which enable them to improve swarming motility and colonization competence (Zeriouh et al, 2014).…”

Bacillus subtilis, the model Gram‐positive bacterium: 20 years of annotation refinement

“…A significant number of genes are indeed explicitly involved in direct interaction with plants [e.g. roots (Habib et al ., 2017), or leaves (Zeriouh et al ., 2014)], either positively or as scavengers of metabolites such as rhamnosides from decaying plants. As a case in point, among many other examples, YfmS, a chemotaxis sensory transducer recognizing a still unknown substrate is involved in the colonization of Arabidopsis thaliana roots (Allard‐Massicotte et al ., 2017).…”

Unusual Biosynthesis and Structure of Locillomycins from Bacillus subtilis 916

“…Among the nonribosomally generated amphipathic cyclic lipopeptides, surfactins, iturins, and fengycins have well-recognized potential applications in biotechnology and biopharmaceutical products due to their antagonistic activities and surfactant properties (2,3). Furthermore, the mechanisms behind the observed biocontrol efficacy of different Bacillus strains have also been well described (4)(5)(6). Lipopeptides are able to induce systemic resistance in plants and to facilitate the multicellular behaviors of the producing strains, such as swarming motility, biofilm formation, and colony morphology (5)(6)(7).…”

“…Furthermore, the mechanisms behind the observed biocontrol efficacy of different Bacillus strains have also been well described (4)(5)(6). Lipopeptides are able to induce systemic resistance in plants and to facilitate the multicellular behaviors of the producing strains, such as swarming motility, biofilm formation, and colony morphology (5)(6)(7).…”