title: Polymyxin P is the active principle in suppressing phytopathogenic Erwinia spp. by the biocontrol rhizobacterium Paenibacillus polymyxa M-1.
abstract: BACKGROUND
  Nine gene clusters dedicated to nonribosomal synthesis of secondary metabolites with possible antimicrobial action, including polymyxin and fusaricidin, were detected within the whole genome sequence of the plant growth-promoting rhizobacterium (PGPR) Paenibacillus polymyxa M-1. To survey the antimicrobial compounds expressed by M-1 we analyzed the active principle suppressing phytopathogenic Erwinia spp.
  
  
  RESULTS
  P. polymyxa M-1 suppressed the growth of phytopathogenic Erwinia amylovora Ea 273, and E. carotovora, the causative agents of fire blight and soft rot, respectively. By MALDI-TOF mass spectrometry and reversed-phase high-performance liquid chromatography (RP-HPLC), two antibacterial compounds bearing molecular masses of 1190.9 Da and 1176.9 Da were detected as being the two components of polymyxin P, polymyxin P1 and P2, respectively. The active principle acting against the two Erwinia strains was isolated from TLC plates and identified by postsource decay (PSD)-MALDI-TOF mass spectrometry as polymyxin P1 and polymyxin P2. These findings were corroborated by domain structure analysis of the polymyxin (pmx) gene cluster detected in the M-1 chromosome which revealed that corresponding to the chemical structure of polymyxin P, the gene cluster is encoding D-Phe in position 6 and L-Thr in position 7.
  
  
  CONCLUSIONS
  Identical morphological changes in the cell wall of the bacterial phytopathogens treated with either crude polymyxin P or culture supernatant of M-1 corroborated that polymyxin P is the main component of the biocontrol effect exerted by strain M-1 against phytopathogenic Erwinia spp.
authors.forename: Ben
authors.initials: B
authors.lastname: Niu
authors.forename: Joachim
authors.initials: J
authors.lastname: Vater
authors.forename: Christian
authors.initials: C
authors.lastname: Rueckert
authors.forename: Jochen
authors.initials: J
authors.lastname: Blom
authors.forename: Maik
authors.initials: M
authors.lastname: Lehmann
authors.forename: Jin-Jiang
authors.initials: JJ
authors.lastname: Ru
authors.forename: Xiao-Hua
authors.initials: XH
authors.lastname: Chen
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Rainer
authors.initials: R
authors.lastname: Borriss
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D061046:Biological Control Agents; D002473:Cell Wall / Q000648:ultrastructure; D004885:Erwinia / Q000166:cytology / Q000187:drug effects*; D005810:Multigene Family; D056507:Paenibacillus / Q000737:chemistry* / Q000235:genetics; D011113:Polymyxins / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D061046:Biological Control Agents; D011113:Polymyxins