DegU and YczE Positively Regulate the Synthesis of Bacillomycin D byBacillus amyloliquefaciensStrain FZB42

Abstract

Environmental strain Bacillus amyloliquefaciens FZB42 differs from the domesticated model organism of the same genus, Bacillus subtilis 168, in its ability to promote plant growth and suppress plant-pathogenic organisms present in the rhizosphere. This behavior is exerted mainly through the production of several nonribosomal cyclic lipopeptides and polyketides, which exhibit a broad range of action against phytopathogenic bacteria, fungi, and nematodes. Here, we provide evidence that the synthesis of the main antifungal agent of B. amyloliquefaciens Plant growth-promoting Bacillus amyloliquefaciens strain FZB42 is applied as a biocontrol agent, as it suppresses soilborne plant-pathogenic organisms. Its antagonistic function is attributed mainly to its ability to produce several secondary metabolites with antibacterial and antifungal activities (5). We have previously reported that FZB42 is a producer of the antibacterial polyketides bacillaene, difficidin/oxydifficidin (6), and a third polyketide which has been identified recently as macrolactin (5). Three cyclic lipopeptides are also produced by B. amyloliquefaciens FZB42 (referred to hereafter as FZB42): surfactin, fengycin, and bacillomycin D. Bacillomycin D has been shown to exert the main antifungal activity (20).Bacillomycin D belongs to the iturin family of lipopeptides, with members such as iturin A and mycosubtilin. It is a cyclic heptapeptide with a ␤-amino fatty acid moiety and is synthesized nonribosomally according to the multicarrier thiotemplate mechanism (40). The bmy operon (37.2 kb) directs the biosynthesis of bacillomycin D and consists of four genes (bmyD, bmyA, bmyB, and bmyC) without orthologues in Bacillus subtilis 168. Several studies have elucidated the physicochemical and biological properties of peptides that belong to the iturin group (3, 25, 34). The chemical principles for the biosynthesis of iturin-like compounds are also largely characterized (12, 44). In contrast, little is known about the regulatory mechanisms that control the expression of the iturin-like lipopeptides (13).Nonribosomal peptide synthetases require posttranslational modification to be functionally active (14). In bacilli, this is achieved by the sfp gene, which encodes a 4Ј-phosphopantetheinyl transferase and posttranslationally converts inactive apoenzyme peptide synthetases to their active holoenzyme forms (14, 18). Strains containing intact synthetases but a dysfunctional sfp gene, such as B. subtilis 168, which contains intact srf and fen operons but has a frameshift mutation in the sfp gene (27), are unable to produce the antibiotics. However, when B. subtilis 168 is complemented with a functional 4Ј-phosphopantetheinyl transferase, its antibiotic production is restored (30,45).It has also been reported that increased expression of the pleiotropic regulator DegQ in B. subtilis 168 (1) enhances the antibiotic production (45, 46). Interestingly, most of the natural Bacillus isolates that express peptide antibiotics show significantly elevated degQ expression c...

Plantazolicin, a Novel Microcin B17/Streptolysin S-Like Natural Product from Bacillus amyloliquefaciens FZB42

“…In this transposon mutant, pMarA was integrated into the degU gene, which is a global transcriptional regulator that activates the bacillomycin D promoter (20). Coincidentally, we observed by high-performance liquid chromatography (HPLC)-electrospray ionization mass spectrometry (ESI-MS) that PZN is overproduced by this strain (see Fig.…”

“…The nonconcentrated, cell surface extract of RSpMarA2, the strain which bears a mariner transposon insertion in the degU global transcriptional regulator gene (20), contains significantly higher levels of cpd1335 than those in the wild type and the RS6 mutant strain (Table 1; Fig. 3A).…”

Amylocyclicin, a Novel Circular Bacteriocin Produced by Bacillus amyloliquefaciens FZB42

“…Sequencing of the region next to the transposon insertion revealed that in mutant WY01, the RBAM_029230 gene was interrupted by the transposon insertion, while mutant RSpMarA2 harbored an interrupted degU gene, suggesting that synthesis of the antibacterial compound is strictly dependent on DegU. DegU, a global transcription regulator, activates the nonribosomal synthesis of the polyketide difficidin, the antifungal lipopeptide bacillomycin D, and bacilysin in FZB42 (23,24).…”

Involvement of Nitrogen Regulation in Bacillus subtilis degU Expression

“…One such example is the Bacillus subtilis DegS-DegU pair, which controls various cellular processes. These include competence development (6,10,11,25), swarming, flagellum formation (1,16), biofilm formation (15,35), osmotic response (29), poly-␥-glutamic acid synthesis (35), salt resistance (19), antibiotic synthesis (17), and the synthesis of extracellular degradative enzymes (21). It has been proposed that some of the events regulated by the DegS-DegU system are manifested by different extents of phosphorylation of the response regulator DegU by the DegS kinase (16,40).…”