Ecological fitness of Bacillus subtilis BGS3 regarding production of the surfactin lipopeptide in the rhizosphere

Abstract

Cyclic lipopeptides and particularly surfactins produced by Bacillus species retain antibacterial, antiviral, biofilm-forming and plant resistance-inducing activities. In most cases, their role in biological control of plant diseases was evoked on the basis of in vitro assays or by using non-producing/overproducing mutants but there is a need for more direct evidence of an efficient lipopeptide biosynthesis in the rhizosphere. In this work, we coupled LC-MS quantification of the lipopeptides secreted by cells colonizing tomato plants with the use of psrfA-lacZ reporter system integrated within the BGS3 chromosome to study the expression of the surfactin operon in planta. Results showed that a higher level of psrfA induction was observed upon the establishment of a stable BGS3 population on roots and surfactins extracted from the rhizosphere were produced in biologically significant quantities. Our results also demonstrate that BGS3 efficiently utilizes the main substrates from plant exudates to produce surfactins. This synthesis is also efficient in cells forming colonies and the production may be favoured in bacteria developing slowly in the rhizosphere. This provides a first understanding of how environmental factors may influence lipopeptide production by beneficial Bacillus strains.

Stimulation of Fengycin-Type Antifungal Lipopeptides in Bacillus amyloliquefaciens in the Presence of the Maize Fungal Pathogen Rhizomucor variabilis

“…Since B. amyloliquefaciens CH2 is still able to slightly inhibit the growth of the phytopathogen, iturins may contribute albeit to a much lower extent, to antifungal activity. The importance of fengycins in the global antifungal effect of Bacillus toward R. variabilis was also supported by the inhibitory activity of B. subtilis 2504, a derivative of the non-active B. subtilis 168, in which efficient production of fengycins was restored (Ongena et al, 2007; Nihorimbere et al, 2009). …”

Stimulation of Defense Reactions in Medicago truncatula by Antagonistic Lipopeptides from Paenibacillus sp. Strain B2

“…The present work has shown that a high level of protection against F. acuminatum in M. truncatula can be obtained using paenimyxin at a concentration that is not phytotoxic and that a part of the mechanisms involved may also act through the plant. Multiple strains of PGPR or its cyclic lipopeptides were demonstrated to stimulate plant defense responses (23,36,51), and the amount of cyclic lipopeptide synthesized in situ has been shown, for Bacillus subtilis, to be in the same range as that used in this work (33). When taken into consideration, these bacteria and their produced molecules are potentially very interesting for the promotion of plant protection.…”

High-Level Biosynthesis of the Anteiso-C 17 Isoform of the Antibiotic Mycosubtilin in Bacillus subtilis and Characterization of Its Candidacidal Activity

“…The resulting srfAB-ERY-srfAD cassette was then used to transform B. subtilis RFB107, and transformants were selected on LuriaBertani erythromycin (1 g/ml) plates. Integration by a double-crossing event in the resulting strain RFB112 was verified by analytical PCR using primers R104 and R105 (Table 1) and by liquid chromatography-electrospray ionization-mass spectrometry analysis of the purified culture supernatant as described elsewhere (14).…”