Abstract
Strain M2T was isolated from the beach of Cuxhaven, Wadden Sea, Germany, in course of a program to attain new producers of bioactive natural products. Strain M2T produces litoralimycin and sulfomycin-type thiopeptides. Bioinformatic analysis revealed a potential biosynthetic gene cluster encoding for the M2T thiopeptides. The strain is Gram-stain-positive, rod shaped, non-motile, spore forming, showing a yellow colony color and forms extensively branched substrate mycelium and aerial hyphae. Inferred from the 16S rRNA gene phylogeny strain M2T affiliates with the genus Streptomonospora. It shows 96.6% 16S rRNA gene sequence similarity to the type species Streptomonospora salina DSM 44593 T and forms a distinct branch with Streptomonospora sediminis DSM 45723 T with 97.0% 16S rRNA gene sequence similarity. Genome-based phylogenetic analysis revealed that M2T is closely related to Streptomonospora alba YIM 90003 T with a digital DNA-DNA hybridisation (dDDH) value of 26.6%. The predominant menaquinones of M2T are MK-10(H6), MK-10(H8), and MK-11(H6) (> 10%). Major cellular fatty acids are iso-C16:0, anteiso C17:0 and C18:0 10-methyl. The polar lipid profile consisted of diphosphatidylglycerol phosphatidyl glycerol, phosphatidylinositol, phosphatidylcholine, phosphatidylethanolamine, three glycolipids, two unknown phospholipids, and two unknown lipids. The genome size of type strain M2T is 5,878,427 bp with 72.1 mol % G + C content. Based on the results obtained from phylogenetic and chemotaxonomic studies, strain M2T (= DSM 106425 T = NCCB 100650 T) is considered to represent a novel species within the genus Streptomonospora for which the name Streptomonospora litoralis sp. nov. is proposed.
Highlights
Despite the increasing number of infectious diseases caused by drug resistant bacteria, the development of new antibiotics by the pharmaceutical industry has largely been abandoned because it is challenging and not lucrative (World Health Organization 2017)
We report on the identification of sulfomycins 3–5 as further thiopeptide secondary metabolites from M2T, as well as the assignment of a putative biosynthetic gene cluster encoding the biosynthesis of the M2T thiopeptide compounds
The comparison of the 16S rRNA gene sequence from strain M2T with 16S gene sequences deposited at the EzTaxon database (EzBioCloud.net) revealed that M2Tshowed closest relationship to strains belonging to the genus Streptomonospora
Summary
Despite the increasing number of infectious diseases caused by drug resistant bacteria, the development of new antibiotics by the pharmaceutical industry has largely been abandoned because it is challenging and not lucrative (World Health Organization 2017). Due to the rediscovery of many known compounds from Streptomyces species in the past years, researchers have focused more on rare Actinobacteria (non-Streptomyces) as source to discover new antibiotics (Sivalingam et al 2019). It has become clear that the identification of new antimicrobial compounds is strongly related with the discovery of novel species (Thumar et al 2010). Mining of microorganisms from unexploited or underexplored habitats is considered a promising approach to discover novel antibiotics (Baumann et al 2014). Soil is the most prominent and rich habitat for rare Actinobacteria. Other habitats such as water, ocean sediments, or beach sands can be regarded as neglected in terms of rare Actinobacteria isolation approaches. The ability of rare Actinobacteria to adapt to many different habitats opens up the possibility of finding
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