Stieleriacines, N-Acyl Dehydrotyrosines From the Marine Planctomycete Stieleria neptunia sp. nov.

Abstract

Bacteria of the phylum <i>Planctomycetes</i> occur ubiquitously in marine environments and play important roles in the marine nitrogen- and carbon cycle, for example as scavengers after phototrophic blooms. Here, we describe the isolation and characterization of the planctomycetal strain Enr13^T isolated from a <i>Posidonia</i> sp. biofilm obtained from seawater sediment close to Panarea Island, Italy. Phylogenetic tree reconstruction based on 16S rRNA gene sequences and multi-locus sequence analysis supports the delineation of strain Enr13^T from characterized species part of the phylum of <i>Planctomycetes</i>. HPLC-MS analysis of culture broth obtained from strain Enr13^T revealed the presence of lipophilic metabolites, of which the major compound was isolated by preparative reversed-phase HPLC. The structure of this compound, named stieleriacine D (<b>1</b>), was elucidated utilizing HRESIMS, 1D- and 2D-NMR data as a new <i>N</i>-acylated dehydrotyrosine derivative. Its biosynthesis was proposed based on an <i>in silico</i> gene cluster analysis. Through analysis of the MS/MS spectrum of <b>1</b> and its minor derivative, stieleriacine E (<b>2</b>), it was possible to assign the structure of <b>2</b> without isolation. <b>1</b> showed antibacterial activity, however, the wide distribution of structurally related compounds indicates a potential role as a signaling molecule.