Boronated Tartrolon Antibiotic Produced by Symbiotic Cellulose-Degrading Bacteria in Shipworm Gills

Shipworms are marine wood-boring bivalve mollusks (family Teredinidae) that harbor a community of closely related Gammaproteobacteria as intracellular endosymbionts in their gills. These symbionts have been proposed to assist the shipworm host in cellulose digestion and have been shown to play a role in nitrogen fixation. The genome of one strain of Teredinibacter turnerae, the first shipworm symbiont to be cultivated, was sequenced, revealing potential as a rich source of polyketides and nonribosomal peptides. Bioassay-guided fractionation led to the isolation and identification of two macrodioloide polyketides belonging to the tartrolon class. Both compounds were found to possess antibacterial properties, and the major compound was found to inhibit other shipworm symbiont strains and various pathogenic bacteria. The gene cluster responsible for the synthesis of these compounds was identified and characterized, and the ketosynthase domains were analyzed phylogenetically. Reverse-transcription PCR in addition to liquid chromatography and high-resolution mass spectrometry and tandem mass spectrometry revealed the transcription of these genes and the presence of the compounds in the shipworm, suggesting that the gene cluster is expressed in vivo and that the compounds may fulfill a specific function for the shipworm host. This study reports tartrolon polyketides from a shipworm symbiont and unveils the biosynthetic gene cluster of a member of this class of compounds, which might reveal the mechanism by which these bioactive metabolites are biosynthesized

Structure and biological activity of a turripeptide from Unedogemmula bisaya venom

The turripeptide ubi3a was isolated from the venom of the marine gastropod Unedogemmula bisaya, family Turridae, by bioassay-guided purification; both native and synthetic ubi3a elicited prolonged tremors when injected intracranially into mice. The sequence of the peptide, DCCOCOAGAVRCRFACC-NH2 (O = 4-hydroxyproline) follows the framework III pattern for cysteines (CC-C-C-CC) in the M-superfamily of conopeptides. The three-dimensional structure determined by NMR spectroscopy indicated a disulfide connectivity that is not found in conopeptides with the cysteine framework III: C-1-C-4, C-2-C-6, C-3-C-5. The peptide inhibited the activity of the alpha 9 alpha 10 nicotinic acetylcholine receptor with relatively low affinity (IC50, 10.2 mu M). Initial Constellation Pharmacology data revealed an excitatory activity of ubi3a on a specific subset of mouse dorsal root ganglion neurons

Boronated tartrolon antibiotic produced by symbiotic cellulose-degrading bacteria in shipworm gills

Shipworms are marine wood-boring bivalve mollusks (family Teredinidae) that harbor a community of closely related Gammaproteobacteria as intracellular endosymbionts in their gills. These symbionts have been proposed to assist the shipworm host in cellulose digestion and have been shown to play a role in nitrogen fixation. The genome of one strain of Teredinibacter turnerae, the first shipworm symbiont to be cultivated, was sequenced, revealing potential as a rich source of polyketides and nonribosomal peptides. Bioassay-guided fractionation led to the isolation and identification of two macrodioloide polyketides belonging to the tartrolon class. Both compounds were found to possess antibacterial properties, and the major compound was found to inhibit other shipworm symbiont strains and various pathogenic bacteria. The gene cluster responsible for the synthesis of these compounds was identified and characterized, and the ketosynthase domains were analyzed phylogenetically. Reverse-transcription PCR in addition to liquid chromatography and high-resolution mass spectrometry and tandem mass spectrometry revealed the transcription of these genes and the presence of the compounds in the shipworm, suggesting that the gene cluster is expressed in vivo and that the compounds may fulfill a specific function for the shipworm host. This study reports tartrolon polyketides from a shipworm symbiont and unveils the biosynthetic gene cluster of a member of this class of compounds, which might reveal the mechanism by which these bioactive metabolites are biosynthesized

Totopotensamides, Polyketide–Cyclic Peptide Hybrids from a Mollusk-Associated Bacterium <i>Streptomyces</i> sp.

Two new compounds, the peptide–polyketide glycoside totopotensamide A (<b>1</b>) and its aglycone totopotensamide B (<b>2</b>), were isolated from a <i>Streptomyces</i> sp. cultivated from the gastropod mollusk <i>Lienardia totopotens</i> collected in the Philippines. The compounds contain a previously undescribed polyketide component, a novel 2,3-diaminobutyric acid-containing macrolactam, and a new amino acid, 4-chloro-5,7-dihydroxy-6-methylphenylglycine. The application of Marfey’s method to phenylglycine derivatives was explored using quantum mechanical calculations and NMR