Gerc, Amy J., Song, Lijiang, Challis, Gregory L., Stanley-Wall, Nicola R. and Coulthurst, Sarah J. (2012) The insect pathogen Serratia marcescens Db10 uses a hybrid non-ribosomal peptide synthetase-polyketide synthase to produce the antibiotic althiomycin. PLoS One, Vol.7 (No.9). e44673. doi:10.1371/journal.pone.0044673

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Abstract

There is a continuing need to discover new bioactive natural products, such as antibiotics, in genetically-amenable micro-organisms. We observed that the enteric insect pathogen, Serratia marcescens Db10, produced a diffusible compound that inhibited the growth of Bacillis subtilis and Staphyloccocus aureus. Mapping the genetic locus required for this activity revealed a putative natural product biosynthetic gene cluster, further defined to a six-gene operon named alb1-alb6. Bioinformatic analysis of the proteins encoded by alb1-6 predicted a hybrid non-ribosomal peptide synthetase-polyketide synthase (NRPS-PKS) assembly line (Alb4/5/6), tailoring enzymes (Alb2/3) and an export/resistance protein (Alb1), and suggested that the machinery assembled althiomycin or a related molecule. Althiomycin is a ribosome-inhibiting antibiotic whose biosynthetic machinery had been elusive for decades. Chromatographic and spectroscopic analyses confirmed that wild type S. marcescens produced althiomycin and that production was eliminated on disruption of the alb gene cluster. Construction of mutants with in-frame deletions of specific alb genes demonstrated that Alb2-Alb5 were essential for althiomycin production, whereas Alb6 was required for maximal production of the antibiotic. A phosphopantetheinyl transferase enzyme required for althiomycin biosynthesis was also identified. Expression of Alb1, a predicted major facilitator superfamily efflux pump, conferred althiomycin resistance on another, sensitive, strain of S. marcescens. This is the first report of althiomycin production outside of the Myxobacteria or Streptomyces and paves the way for future exploitation of the biosynthetic machinery, since S. marcescens represents a convenient and tractable producing organism.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QH Natural history > QH301 Biology R Medicine > RS Pharmacy and materia medica
Divisions:	Faculty of Science > Chemistry
Library of Congress Subject Headings (LCSH):	Serratia marcescens -- Genetics, Antibiotics -- Synthesis
Journal or Publication Title:	PLoS One
Publisher:	Public Library of Science
ISSN:	1932-6203
Official Date:	September 2012
Dates:	Date Event September 2012 Published
Date of first compliant deposit:	22 December 2015
Date of first compliant Open Access:	22 December 2015
Volume:	Vol.7
Number:	No.9
Page Range:	e44673
DOI:	10.1371/journal.pone.0044673
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access
Funder:	Royal Society of Edinburgh, Scotland, Wellcome Trust (London, England), Advantage West Midlands (AWM), European Regional Development Fund (ERDF)
Grant number:	093711/B/10/Z (WT)

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