Streptomyces lunaelactis sp. nov., a novel ferroverdin A-producing Streptomyces species isolated from a moonmilk speleothem

摘要

A novel actinobacterium, designated MM109T, was isolated from a moonmilk deposit collected from the cave ‘Grotte des Collemboles’ located in Comblain-au-Pont, Belgium. Based on a polyphasic taxonomic approach comprising chemotaxonomic, phylogenetic, morphological, and physiological characterization, the isolate has been affiliated to the genus Streptomyces. Multilocus sequence analysis based on the 16S rRNA gene and five other house-keeping genes (atpD, gyrB, rpoB, recA and trpB) showed that the MM109T isolate is sufficiently distinct from its closest relative, Streptomyces peucetius strain AS 4.1799T, as to represent a novel species. The phylogenetic distinctiveness of the taxon represented by isolate MM109T was supported by the isolation and identification of additional twelve moonmilk-derived isolates, which according to multilocus sequence analysis were clustered along with MM109T. Scanning electron microscopy observations revealed complex and diversified structures within a MM109T colony, made from branching vegetative mycelia. The spore chains of the MM109T isolate undergo complete septation at the late stages of the morphological differentiation process, leading to the formation of packs of smooth cylindrical-shaped spores. Isolate MM109T produces several intracellular and diffusible pigments, particularly an intracellular green-pigmented secondary metabolite, which was identified through UPLC-ESI–MS analysis as ferroverdin A, an iron-chelating molecule formerly extracted and characterized from Streptomyces sp. strain WK-5344. The isolate MM109T is thus considered to represent a novel species of Streptomyces, for which the name Streptomyces lunaelactis sp. nov. is proposed with the type strain MM109T (=DSM 42149T = BCCM/LMG 28326T).