title: Characterization of lipopeptides produced by Bacillus licheniformis using liquid chromatography with accurate tandem mass spectrometry.
abstract: BACKGROUND
  The plant endophyte Bacillus licheniformis, isolated from leaves of Vitis vinifera, was studied to individuate and characterize the presence of bioactive lipopeptides having amino acidic structures.
  
  
  METHODS
  Crude extracts of liquid cultures were analyzed by ultra-high-performance liquid chromatography (UHPLC) coupled to a quadrupole time-of-flight (QTOF) mass analyzer. Chromatographic conditions were optimized in order to obtain an efficient separation of the different isobaric lipopeptides, avoiding merged fragmentations of co-eluted isomeric compounds and reducing possible cross-talk phenomena. Composition of the amino acids was outlined through the interpretation of the fragmentation behavior in tandem high-resolution mass spectrometry (HRMS/MS) mode, which showed both common-class and peculiar fragment ions. Both [M + H](+) and [M + Na](+) precursor ions were fragmented in order to differentiate some isobaric amino acids, i.e. Leu/Ile. Neutral losses characteristic of the iso acyl chain were also evidenced.
  
  
  RESULTS
  More than 90 compounds belonging to the classes of surfactins and lichenysins, known as biosurfactant molecules, were detected. Sequential LC/HRMS/MS analysis was used to identify linear and cyclic lipopeptides, and to single out the presence of a large number of isomers not previously reported. Some critical issues related to the simultaneous selection of different compounds by the quadrupole filter were highlighted and partially solved, leading to tentative assignments of several structures. Linear lichenysins are described here for the first time.
  
  
  CONCLUSIONS
  The approach was proved to be useful for the characterization of non-target lipopeptides, and proposes a rationale MS experimental scheme aimed to investigate the difference in amino acid sequence and/or in the acyl chain of the various congeners, when standards are not available. Results expanded the knowledge about production of linear and cyclic bioactive compounds from Bacillus licheniformis, clarifying the structures of isomeric forms, and enabling the use of selected endophytes to produce fungicides for eco-friendly biocontrol. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy. gabriella.favaro@unipd.it.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Favaro
authors.affiliation: Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy.
authors.forename: Sara
authors.identifier: http://orcid.org/0000-0002-9152-3602
authors.initials: S
authors.lastname: Bogialli
authors.affiliation: Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy.
authors.forename: Iole Maria
authors.initials: IM
authors.lastname: Di Gangi
authors.affiliation: Department of Biology, University of Padova, via Ugo Bassi 58/B, 35131, Padova, Italy.
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Nigris
authors.affiliation: Department of Biology, University of Padova, via Ugo Bassi 58/B, 35131, Padova, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Baldan
authors.affiliation: Department of Agronomy, Animals, Food, Natural Resources and Environment, University of Padova, Viale dell'Università 16, 35020, Legnaro (PD), Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Squartini
authors.affiliation: Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pastore
authors.affiliation: Department of Biology, University of Padova, via Ugo Bassi 58/B, 35131, Padova, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Baldan
mesh_terms: D000069976:Bacillus licheniformis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D055666:Lipopeptides / Q000737:chemistry* / Q000378:metabolism; D018515:Plant Leaves / Q000382:microbiology; D053719:Tandem Mass Spectrometry / Q000379:methods*; D027843:Vitis / Q000382:microbiology
chemical_list: D055666:Lipopeptides