title: Bacillus amyloliquefaciens strain 32a as a source of lipopeptides for biocontrol of Agrobacterium tumefaciens strains.
abstract: OBJECTIVE
  A Bacillus amyloliquefaciens strain, designated 32a, was used to identify new compounds active against Agrobacterium tumefaciens and to evaluate their efficiency to control crown gall on carrot discs.
  
  
  RESULTS
  Based on PCR-assays, four gene clusters were shown to direct the synthesis of the cyclic lipopeptides surfactin, iturin A, bacillomycin D and fengycin. Mass spectrometry analysis of culture supernatant led to the identification of these secondary metabolites, except bacillomycin, with heterogeneous mixture of homologues. Antimicrobial assays using lipopeptides-enriched extract showed a strong inhibitory activity against several bacterial and fungal strains, including Ag. tumefaciens. Biological control assays on carrot discs using both 32a spores and extract resulted in significant protection against crown gall disease, similar to that provided by the reference antagonistic strain Agrobacterium rhizogenes K1026.
  
  
  CONCLUSIONS
  In contrast to all active compounds against Ag. tumefaciens that are of proteinaceous nature, this work enables for the first time to correlate the strong protective effect of B. amyloliquefaciens strain 32a towards crown gall disease with the production of a mixture of lipopeptides.
  
  
  CONCLUSIONS
  The findings could be useful for growers and nursery men who are particularly interested in the biocontrol of the crown gall disease.
authors.affiliation: Biopesticides Team (LPIP), Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
authors.forename: D
authors.initials: D
authors.lastname: Ben Abdallah
authors.affiliation: Biopesticides Team (LPIP), Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
authors.forename: O
authors.initials: O
authors.lastname: Frikha-Gargouri
authors.affiliation: Biopesticides Team (LPIP), Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
authors.forename: S
authors.initials: S
authors.lastname: Tounsi
mesh_terms: D016960:Agrobacterium tumefaciens / Q000187:drug effects* / Q000254:growth & development; D000890:Anti-Infective Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001407:Bacillus / Q000737:chemistry* / Q000378:metabolism; D001419:Bacteria / Q000187:drug effects; D005658:Fungi / Q000187:drug effects; D055666:Lipopeptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data
chemical_list: D000890:Anti-Infective Agents; D055666:Lipopeptides
keywords: Agrobacterium tumefaciens; Bacillus amyloliquefaciens; biological control; crown gall disease; lipopeptides