title: A natural plasmid uniquely encodes two biosynthetic pathways creating a potent anti-MRSA antibiotic.
abstract: BACKGROUND
  Understanding how complex antibiotics are synthesised by their producer bacteria is essential for creation of new families of bioactive compounds. Thiomarinols, produced by marine bacteria belonging to the genus Pseudoalteromonas, are hybrids of two independently active species: the pseudomonic acid mixture, mupirocin, which is used clinically against MRSA, and the pyrrothine core of holomycin.
  
  
  RESULTS
  High throughput DNA sequencing of the complete genome of the producer bacterium revealed a novel 97 kb plasmid, pTML1, consisting almost entirely of two distinct gene clusters. Targeted gene knockouts confirmed the role of these clusters in biosynthesis of the two separate components, pseudomonic acid and the pyrrothine, and identified a putative amide synthetase that joins them together. Feeding mupirocin to a mutant unable to make the endogenous pseudomonic acid created a novel hybrid with the pyrrothine via "mutasynthesis" that allows inhibition of mupirocin-resistant isoleucyl-tRNA synthetase, the mupirocin target. A mutant defective in pyrrothine biosynthesis was also able to incorporate alternative amine substrates.
  
  
  CONCLUSIONS
  Plasmid pTML1 provides a paradigm for combining independent antibiotic biosynthetic pathways or using mutasynthesis to develop a new family of hybrid derivatives that may extend the effective use of mupirocin against MRSA.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Fukuda
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Haines
authors.forename: Zhongshu
authors.initials: Z
authors.lastname: Song
authors.forename: Annabel C
authors.initials: AC
authors.lastname: Murphy
authors.forename: Joanne
authors.initials: J
authors.lastname: Hothersall
authors.forename: Elton R
authors.initials: ER
authors.lastname: Stephens
authors.forename: Rachel
authors.initials: R
authors.lastname: Gurney
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Cox
authors.forename: John
authors.initials: J
authors.lastname: Crosby
authors.forename: Christine L
authors.initials: CL
authors.lastname: Willis
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Simpson
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Thomas
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D053898:Biosynthetic Pathways / Q000235:genetics / Q000502:physiology*; D007769:Lactams / Q000378:metabolism; D055624:Methicillin-Resistant Staphylococcus aureus; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D016712:Mupirocin / Q000096:biosynthesis; D010957:Plasmids / Q000235:genetics; D031161:Pseudoalteromonas / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D007769:Lactams; C015265:holomycin; D016712:Mupirocin