title: Isolation and characterization of diverse antimicrobial lipopeptides produced by Citrobacter and Enterobacter.
abstract: BACKGROUND
  Increasing multidrug-resistance in bacteria resulted in a greater need to find alternative antimicrobial substances that can be used for clinical applications or preservation of food and dairy products. Research on antimicrobial peptides including lipopeptides exhibiting both narrow and broad spectrum inhibition activities is increasing in the recent past. Therefore, the present study was aimed at isolation and characterization of antimicrobial lipopeptide producing bacterial strains from fecal contaminated soil sample.
  
  
  RESULTS
  The phenotypic and 16S rRNA gene sequence analysis of all isolates identified them as different species of Gram-negative genera Citrobacter and Enterobacter. They exhibited common phenotypic traits like citrate utilization, oxidase negative and facultative anaerobic growth. The HPLC analysis of solvent extracts obtained from cell free fermented broth revealed the presence of multiple antimicrobial lipopeptides. The comprehensive mass spectral analysis (MALDI-TOF MS and GC-MS) of HPLC purified fractions of different isolates revealed that the lipopeptides varied in their molecular weight between (m/z) 607.21 to 1536.16 Da. Isomers of mass ion m/z 984/985 Da was produced by all strains. The 1495 Da lipopeptides produced by strains S-3 and S-11 were fengycin analogues and most active against all strains. While amino acid analysis of lipopeptides suggested most of them had similar composition as in iturins, fengycins, kurstakins and surfactins, differences in their β-hydroxy fatty acid content proposed them to be isoforms of these lipopeptides.
  
  
  CONCLUSIONS
  Although antimicrobial producing strains can be used as biocontrol agents in food preservation, strains with ability to produce multiple antimicrobial lipopeptides have potential applications in biotechnology sectors such as pharmaceutical and cosmetic industry. This is the first report on antibacterial lipopeptides production by strains of Citrobacter and Enterobacter.
authors.affiliation: Central Research Facility, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India.
authors.forename: Santi M
authors.initials: SM
authors.lastname: Mandal
authors.forename: Shalley
authors.initials: S
authors.lastname: Sharma
authors.forename: Anil Kumar
authors.initials: AK
authors.lastname: Pinnaka
authors.forename: Annu
authors.initials: A
authors.lastname: Kumari
authors.forename: Suresh
authors.initials: S
authors.lastname: Korpole
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology*; D015373:Bacterial Typing Techniques; D002851:Chromatography, High Pressure Liquid; D002954:Citrobacter / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D016000:Cluster Analysis; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004754:Enterobacter / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D055666:Lipopeptides / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D055666:Lipopeptides; D012336:RNA, Ribosomal, 16S