Turnerbactin, a novel triscatecholate siderophore from the shipworm endosymbiont Teredinibacter turnerae T7901.

TitleTurnerbactin, a novel triscatecholate siderophore from the shipworm endosymbiont Teredinibacter turnerae T7901.
Publication TypeJournal Article
Year of Publication2013
AuthorsHan AW, Sandy M, Fishman B, Trindade-Silva AE, Soares CAG, Distel DL, Butler A, Haygood MG
JournalPLoS One
Volume8
Issue10
Paginatione76151
Date Published2013
ISSN1932-6203
KeywordsAnimals, Bacterial Proteins, Benzoates, Bivalvia, Catechols, Gammaproteobacteria, Gene Expression, Genome, Bacterial, Gills, Hydroxybenzoates, Iron, Metabolic Networks and Pathways, Multigene Family, Mutation, Nitrogen Fixation, Oligopeptides, Peptide Synthases, Siderophores, Symbiosis
Abstract

Shipworms are marine bivalve mollusks (Family Teredinidae) that use wood for shelter and food. They harbor a group of closely related, yet phylogenetically distinct, bacterial endosymbionts in bacteriocytes located in the gills. This endosymbiotic community is believed to support the host's nutrition in multiple ways, through the production of cellulolytic enzymes and the fixation of nitrogen. The genome of the shipworm endosymbiont Teredinibacter turnerae T7901 was recently sequenced and in addition to the potential for cellulolytic enzymes and diazotrophy, the genome also revealed a rich potential for secondary metabolites. With nine distinct biosynthetic gene clusters, nearly 7% of the genome is dedicated to secondary metabolites. Bioinformatic analyses predict that one of the gene clusters is responsible for the production of a catecholate siderophore. Here we describe this gene cluster in detail and present the siderophore product from this cluster. Genes similar to the entCEBA genes of enterobactin biosynthesis involved in the production and activation of dihydroxybenzoic acid (DHB) are present in this cluster, as well as a two-module non-ribosomal peptide synthetase (NRPS). A novel triscatecholate siderophore, turnerbactin, was isolated from the supernatant of iron-limited T. turnerae T7901 cultures. Turnerbactin is a trimer of N-(2,3-DHB)-L-Orn-L-Ser with the three monomeric units linked by Ser ester linkages. A monomer, dimer, dehydrated dimer, and dehydrated trimer of 2,3-DHB-L-Orn-L-Ser were also found in the supernatant. A link between the gene cluster and siderophore product was made by constructing a NRPS mutant, TtAH03. Siderophores could not be detected in cultures of TtAH03 by HPLC analysis and Fe-binding activity of culture supernatant was significantly reduced. Regulation of the pathway by iron is supported by identification of putative Fur box sequences and observation of increased Fe-binding activity under iron restriction. Evidence of a turnerbactin fragment was found in shipworm extracts, suggesting the production of turnerbactin in the symbiosis.

DOI10.1371/journal.pone.0076151
Alternate JournalPLoS ONE
PubMed ID24146831
PubMed Central IDPMC3795760
Grant List1U01TW008163 / TW / FIC NIH HHS / United States